Class 8

Students can Download Kannada Chapter 1 Natural Resources Questions and Answers, Summary, Notes Pdf, KSEEB Solutions for Class 8 Science, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka Board Class 8 Science Chapter 1 Natural Resources

KSEEB Class 8 Science Chapter 1 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statements. Choose the right answer:

Question 1.
One of the following does not belong to the group.
(a) Water
(b) forests
(c) petrol
(d) soil
Answer:
(c) petrol

Question 2.
Government has banned hunting of wild animals. This helps to.
(a) maintain biodiversity
(b) promote tourism
(c) provide food to animals
(d) maintain soil fertility.
Answer:
(a) maintain biodiversity

II. Fill in the blanks with suitable words:

Question 1.
Resources that get replenished in nature are called …………….
Answer:
Renewable natural resource

Question 2.
Petrol and Kerosene are ……………. forms of natural resources.
Answer:
Non – renewable

Question 3.
If there is rise in water table, soil becomes ………..
Answer:
Saline

Question 4.
Soil provides ……….. and …………… to terrestrial plants.
Answer:
Minerals and water

Question 5.
An example for renewable resources is ……….
Answer:
Solar energy

III. Answer the following:

Question 1.
What are natural resources?
Answer:
The things that occur in nature and that are useful to us are called natural resources.

Question 2.
Differentiate between renewable and non-renewable resources.
Answer:

Renewable Resources:

• These resources can be replenished.
• These are continuously available for use and are inexhaustible.

Non-renewable Resources:

• These resources cannot be replenished.
• They get depleted, i.e. they are exhaustible.

Question 3.
List the uses of water?
Answer:
The uses of water are as follows :

1. Water is very much essential for the existence of life.
2. It is a factor for many aspects of life such as environmental stability, biodiversity conservation, fuel security, and even healthcare.
3. Water is used for various human activities like drinking, agricultural purposes washing, and recreation.
4. Water is used for heat exchange processes industries and fire extinguishers.
5. The largest use of water occurs in the agricultural sector.
6. Water is used for producing electricity by the hydroelectric power plant.

Question 4.
What is mining?
Answer:
Mining is the process of extraction and processing of minerals.

Question 5.
What happens if too many fossil fuels is used?
Answer:
Fossil fuels are non-renewable resources. They Cannot be replenished once depleted. Too much of the usage of fossils fuels leads to energy crises in the near future

Question 6.
A student argues that a nation will be rich if its forests are conserved. Explain
Answer:

1. Forest provides many products like resins gums, dyes, lace, fibers, wax, honey, medicines.
2. Forest provides raw materials for various wood-based industries such as paper, board, rayon, etc.
3. Forest provides timber which is an important material in constructing buildings and furniture.
4. Forest have aesthetic value and provide opportunities in tourism.
5. Therefore the forest plays an important role in the country’s economy.

KSEEB Class 8 Science Natural Resources Additional Questions & Answers

Question 1.
What are the natural resources?
Answer:
The things that occur in nature and that are useful to us are called natural resources.

Question 2.
Give any two examples of living resources.
Answer:
Forest and wildlife are examples of living resources.

Question 3.
Give any Four examples of non¬living resources.
Answer:
Land, water, air and mineral ores are examples of non-living resources.

Question 4.
Give reason
I) water should be used judiciously.
Answer:
Nearly 97% of water on earth is held in ocean and Seas, about 2.4% of water is found in glaciers and polar ice-caps. Only a small percentage is available for human use, therefore, water should be used judiciously.

Question 5.
What are the reasons for the depletion of water?
Answer:
The reason for the depletion of water are :

1. Increase in population.
2. Pollution and Destruction of forests.
3. Improper use of water.

Question 6.
Mention the importance of the soil.
Answer:
The importance of soil as follows :

1. Soil is a natural resource that provides minerals and water to all land plants.
2. Soil is a primary nutrient base for agricultural crops.
3. Soil is the place of living for a wide, variety of organisms like earthworms, crabs, insects, and microorganisms.

Question 7.
How does desertification occur?
Answer:
Due to waterlogging and Salinisation are the main causes of another serious problem in which once fertile lands are becoming barren and useless. This condition is called desertification.

Question 8.
Mention the importance of Forests.
Answer:
The importance of forests are as follows

1. Forest are renewable natural resources that have innumerable contributions to the environment.
2. Forests maintain the water cycle.
3. They provide habitat for wild animals.
4. They maintain Soil quantity by preventing Soil erosion.
5. They provide timber and many other useful products and services.
6. They are indicators of the natural wealth of a nation.

Question 9.
Define the term wildlife.
Answer:
The term wildlife is used to describe the species of plants and animals living in the wild.

Question 10.
What are the reasons for the extinction of many species?
Answer:
The reasons for the extinction of species are.

1. Destruction of their natural habitats.
2. Human activities such as hunting, poaching, and capturing meat, furs, horns skin, ivory, etc…

Question 11.
Write the measures for the conservation of living resources.
Answer:
The measures are taken to conserve the living resources are,

1. Proper maintenance of their natural habitats.
2. Establishment of National Parks, wildlife sanctuaries bird sanctuaries.
3. Restriction or hunting, poaching or animals by strict legislation.
4. Protection of sample population in zoos and botanical gardens and other man-made situations.
5. The Creation of seed banks, gene banks, and similar genetic resource centers.

Question 12.
What are fossils fuels? How are they formed?
Answer:
The non-renewable resources such as Coal, petroleum products and natural gas represents fossil fuels. They are formed by the result of the photosynthetic activity of green plants. Which were existing millions of years ago?

Question 13.
Name the types of coal and their carbon content.
Answer:
The types of coal are

1. Anthracite – Carbon content is about 80%, it is very hard.
2. Lignite – Carbon content is about 60%-65%.
3. Bituminous Coal – Carbon content is less than 40%.

Question 14.
Name a few petroleum products.
Answer:
Petrol, diesel, Kerosene, lubricating oils and naptha represent various forms of petroleum products.

Question 15.
Natural gas is considered as eco-friendly give reason.
Answer:
The low sulphur content of natural gas makes it the least pollutive Source of fuel. Therefore it is considered eco-friendly fuel.

Question 16.
What are minerals?
Answer:
Minerals the metallic compounds, naturally found in the earth’s crust and not formed from living matters.

Question 17.
Minerals are also considered as non-renewable resources. Give reason.
Answer:
The rule of formation of such minerals is very slow compared to the rate at which they are being used by human Such resources which cannot be replenished. Once depleted are called Non-renewable resources.

Question 18.
Non-Renewable Resources are popular why?
Answer:

1. Gives energy quickly
2. Easy to store and transportation is easy.
3. High efficiency
4. Leaves no residue

 

 

Karnataka Board Class 8 Science Chapter 15 Heat

KSEEB Class 8 Science Chapter 15 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statements/questions. Choose the right answer.

Question 1.
When an object is heated, the molecules that make up the object
a) begin to move faster
b) lose energy
c) become heavier
d) become lighter
Answer:
a) begin to move faster

Question 2.
The temperature of a body is an indicator of
a) The total energy of the molecules of an object
b) The average energy of the molecules of an object
c) The total velocity of the molecules of the object
d) The average kinetic energy of the. molecules of an object.
Answer:
d) The average kinetic energy of the molecules of an object.

Question 3.
A and B are two objects. The temperature of A is greater than that of B. This means that
a) The molecules of A move faster on an average than the molecules of B
b) The total energy of A is greater than the total energy of the molecules of B
c) The average potential energy of A is greater than the average potential energy of B.
d) The heat content of A will always be greater than that of B.
Answer:
a) The molecules of A move faster on an average than the molecules of B

II. Fill in the blanks with suitable words.

Question 1.
The degree of hot or cold of a body is called ………
Answer:
heat/temperature

Question 2.
Temperature is expressed in degree ……………….
Answer:
degree centigrade/ Joule

Question 3.
Substances changes from liquid to a gas at a constant temperature, it is called …………
Answer:
condensation/boiling point

Question 4.
The temperature of boiling water in the Celsius scale of temperature is ……………
Answer:
C (100/373/212/32)

Question 5.
The SI unit of heat is ……………..
Answer:
Joule/ Celsius

III. State whether the following statement is true or False :

Question 1.
Liquid expands on heating
Answer:
True

Question 2.
The unit of heat and temperature are the same
Answer:
False

Question 3.
The bi-metal strip is used in Fan
Answer:
False

IV. Answer the following:

Question 1.
Distinguish between heat and temperature.
Answer:

1. Heat :
   • Heat is a form of energy
   • Heat energy depends upon the speed of the particles, the number of particles and size or mass, and the type of particles in an object.
   • It is the sum of energies of all molecules,
   • SI unit of heat is Joule.
2. Temperature :
   • Temperature is a measure of the degree of hot or cold. lt is a number that is related to energy, but it is not energy itself.
   • Temperature does not depend on the size or mass of an object. For example, the temperature of a small cup of water is the same as the temperature of a tub of water.
   • It is the average kinetic energy of the molecules.
   • SI unit of temperature is Kelvin.

Question 2.
Mention three different effect produced by heat.
Answer:
The three effects produced by heat are

1. Increase in temperature
2. Thermal expansion
3. Change in the physical state
4. Change in chemical change

Question 3.
Give one example to illustrate that heat can be generated from the energy of motion.
Answer:
If we rub our palms vigorously or rubbing a metal strip of an iron nail on a stone several times that is produced. There are examples to illustrate that heat can be generated from the energy of motion.

Question 4.
Describe an experiment to prove that solids expand on heating.
Answer:

Take two aluminum rods measuring 7 cm each to fix it to a stand with a paper-thin gap between the rods. Connect to a circuit. Heat the rod by a spirit lamp. Due to heat rods expand and touch each making the circuit closed. The bulb burns. This shows that solids expand due to heat.

Question 5.
Name two devices which use bimetallic strip.
Answer:
Thermal expansion of bimetallic strips used as a heat operated switch in the circuit of automatic equipment like an iron box, fire alarms, electric heater, etc. Some thermometers work on the principle of expansion of liquids In automobile engines useful work is done by the expansion of gases.

Question 6.
A Thick glass tumbler often cracks when boiling water is poured into it why?
Answer:
If we put boiling water in a thick glass tumbler. It cracks immediately, this is due to the fact that glass is a poor conductor of heat. When boiling water is put in the glass tumbler the inner surface of the glass becomes hot. So the wall expands, But the outer surface of the glass wall does not expand quickly. This uneven expansion cracks the glass.

Question 7.
State similarities and differences between the laboratory thermometer and the clinical thermometer.
Answer:
Similarities:
The laboratory or clinical thermometer is used to measure temperature or temperature changes. They are made of glass with mercury. Both are made on the property of the expansion of liquids on heating.
Differences:

1. Laboratory thermometer
   • Used to measure the temperature of any substance
   • has a long graduated capillary tube
   • The range of laboratory thermometer is 0°C to 100°C
2. Clinical thermometer
   • Used to measure the only temperature in Humans or animals
   • has a short capillary tube with a narrow constriction
   • The range of clinical thermometer 3 5°C to 42°C

Question 8.
Convert 100°F into Celsius and Kelvin scale of temperature.
Answer:
°C = \(\frac { 5 }{ 9 }\) ( °F – 32 )
°C = \(\frac { 5 }{ 9 }\) ( 100 –  32 )
°C = \(\frac { 5 }{ 9 }\) × 68 = \(\frac { 340 }{ 9 }\)
°C = 39.77 = 40°
I = °C + 273
k = 40 + 273
k = 313

V . Match the following

Answer:

1. g
2. F
3. e
4. b

KSEEB Class 8 Science Chapter 15 Additional Questions & Answers

Question 1.
What is the temperature?
Answer:
An increase in average kinetic energy is called temperature.

Question 2.
What is meant by heat?
Answer:
The total kinetic energy of all the molecules in a substance is called heat. The SI unit of heat is Joule (J)

Question 3.
Mention the different effect produced by heat.
Answer:
The three effect produced by heat are

1. Increase in temperature
2. Thermal expansion
3. Change in physical state
4. Chemical change

Question 4.
In industries, metal pipelines are provided with loops at regular intervals. Why?
Answer:
In industries, hot water or molten liquid is transferred from one place to another through metal pipelines. The expansion and contraction might bend or break the pipe. To overcome this, these metal pipelines are provided with loops at regular intervals. The expansion of pipelines causes the size of the loop to increase slightly so the pipe does not break.

Question 5.
Mention the application of thermal expansion.
Answer:
Thermal expansion of bimetallic strips used as a heat operated switch in the circuit of automatic equipment like an iron box, fire alarms, electric heater etc. Some thermometers work on the principle of expansion of liquids In automobile engines useful work is done by the expansion of gases.

Question 6.
What is meant by anomalous expansion?
Answer:
The sensual property of water between 0°C to 4°C is called anomalous expansion i.e. water on cooling contracts up to 4°C and afterward it starts expanding till it freezes into ice at 0° C.

Question 7.
What is a thermometer?
Answer:
A thermometer is an instrument that measures the temperature of a system quantitatively.

Question 8.
Name different types of thermometers.
Answer:
There are three commonly used scales of temperature.

1. Celsius scale of temperature  °C
2. Fahrenheit scale of temperature °F
3. Kelvin scale of temperature  K

Question 9.
What do you mean by the Bimetallic strip thermometer?
Answer:
Bimetallic strip thermometers include two different metals that are bonded together and expand at different rates as they warm up often, long bimetallic, strips are wound into a coil and used with a dial they have a different rate of exemption.

Question 10.
Draw a diagram of a Laboratory thermometer.
Answer:

Question 11.
Draw a diagram of a clinical thermometer.
Answer:

Question 12.
Mention the two special features of the clinical thermometer.
Answer:
The capillary has a narrow bend called constriction. The range of clinical thermometer is between 35° C and 42° C.

Question 13.
What are the precautions to be taken while using a clinical thermometer?
Answer:

1. Precautions to be taken while using a clinical thermometer.
2. The thermometer should be washed before and after each use, preferably with an antiseptic solution.
3. Do not wash the thermometer with hot water.
4. Ensure that before use the mercury level is below 35° C.
5. Read the thermometer keeping the level of mercury along the line of sight.
6. Handle the thermometer with care, as you handle any glass articles.
7. Don’t hold the thermometer by the bulb while reading it.

Question 14.
Write an experiment to find the boiling point of water?
Answer:

Take about 50 Cm³ of water in a round -bottom flask and add a few fragments of broken porcelain. Heat the flask and note the temperature when boiling begins. Take readings every thirty seconds for five minutes, i.e., ten readings in all. and take the average as the boiling point.

Question 15.
Write the principle on which the thermometer is made.
Answer:
The thermometer is made on the property of the expansion of liquids on heating.

Question 16.
How does a pressure cooker work?
Answer:
As the pressure increases the boiling point of water also increases. In the pressure cookers the boiling point of water increases due to the pressure created by blocking of the steam by weight. The weight rises up and lets out the steam of the pressure crosses a certain limit. Due to the increases in the boiling points, the food substances are cooked within less time. Thus it saves energy.

Question 17.
Write an experiment to show the melting point of ice.
Answer:

Small ice cubes are taken in a Funnel. The funnel is fixed to a stand as shown in Figure. The thermometer bulb is kept in the funnel such that it is surrounded by ice cubes, keeps a glass bottle below the funnel. Ice begins to melt utilizing the heat of the surrounding air. Water thus formed drops out of the funnel. After 10 minutes note down the level of mercury in the thermometer and take the reading which shows the melting point of ice.

Question 18.
At what temperature do the Celsius and Fahrenheit thermometers show the same measurement? Prove it by calculation.
Answer:
Celsius scale has divisions between 0 and 100 while the Fahrenheit has divisions from 32 to 212 ie. 180 divisions. Since Celsius and Fahrenheit scales are equal.
\(\begin{array}{l}{\frac{C-0}{100}=\frac{F-32}{180}} \\ {C=\frac{5}{9}(F-32)} \\ {F=\frac{9}{5} C+32}\end{array}\)
∴ – 40° C = – 40°F
Give scientific reasons:

Question 19.
Ice melts when heated.
Answer:
Every solid substance melt at a definite temperature on heating. Hence, when we heat ice, the kinetic energy increases and they get separated and free to move.

Question 20.
Telephone wires sag during summer.
Answer:
The metallic wires tend to expand due to the heat of the summer, therefore they sag.

Question 21.
Space is left between small stretches while making cemented roads.
Answer:
Space is left between small stretches while making cemented roads in order to avoid accidents due to the expansion.

Question 22.
Before use, the clinical thermometer is jerked.
Answer:
Before use, the clinical thermometer is jerked so that the mercury flows back into the bulb.

Question 23.
Water cannot be used as a liquid in a thermometer.
Answer:

1. The capillary tube required to be very long.
2. The increase in the water level cannot be easily visible.

Question 24.
Common salt is added to ice.
Answer:
Common salt is added to ice in order to reduce the melting point so that ice will not melt soon.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 19 Nutrition and Respiration

KSEEB Class 8 Science Chapter 19 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement/ question. Choose the right answer.

Question 1.
The process of obtaining food and utilizing it in the body is ……………
(a) respiration
(b) nutrition
(c) excretion
(d) reproduction.
Answer:
(b) nutrition

Question 2.
One of these is a product of photosynthesis …………….
(a) Starch
(b) glucose
(c) Maltose
(d) sucrose.
Answer:
(a) Starch

Question 3.
Insectivorous plants commonly grow in areas where soil is deficient in
(a) carbon
(b) nitrogen
(c) potassium
(d) phosphorus.
Answer:
(b) nitrogen

Question 4.
A person applies hydrogen peroxide on his wound This is to kill
a) anaerobic bacteria
b) aerobic bacteria
c) fungi
d) protozoa.
Answer:
c) fungi

Question 5.
Amylase Converts Starch to
(a) glucose
(b) Sucrose
(c) lactose
(d) maltose
Answer:
(d) maltose

II. Answer the Following.

Question 1.
What are life processes?
Answer:
The processes such as respiration, nutrition, growth, movement, response to stimuli, excretion and reproduction that help to support and sustain life are called as life processes.

Question 2.
Explain the method of testing a leaf for starch.
Answer:
Collect a Few leaves From a plant put it in water For Some time and the take out, It is then dipped in spirit and then in Iodine Solution. Observe that the leaf turns blue-black Showing the presence of Starch.

Question 3.
Explain an experiment to demonstrate that oxygen is released during photosynthesis.
Answer:

Take two troughs Filled with water Add a few Crystals of Sodium bicarbonate to both. Place Hydrilla plants in both the troughs and invert large Funnels over them Take two test tubes, place Small pieces of Steel wool into their bottoms.

Fill the test tubes with water and invert them over the narrow ends of each of the Funnel, place one of the troughs in a bright Sunny area Whereas the other trough in dark Cupboard For about by introduced Splinters.

The Splinter burns brightly in the gas collected in the test tube which is kept outside, but not which is kept in the Cupboard. From this experiment, we can show that the gas released during photosynthesis is oxygen.

Question 4.
Differentiate between the two phases of photosynthesis
Answer:

Light reaction	Dark reaction
1. Light reaction takes place in the presence of sunlight.	1. Dark reaction takes place in the absence of sunlight (night)
2. It takes place in the grana region	2. It takes place in the stroma region

Question 5.
What are parasites? Give two examples.
Answer:
The organism which obtains Food from other organism is called a parasite. There are two types of parasites.

1. Semi parasite
   Eg: Viscum
2. Total parasite
   Eg: Cuscuta, intestinal worms like tapeworm, roundworm, etc.

Question 6.
Amoeba Cannot digest Fats Why?
Answer:
Amoeba has no enzyme to digest Fats Therefore amoeba Cannot digest Fats.

Question 7.
Explain the respiration in the cockroach.
Answer:
The tracheal system of a cockroach includes stigmata, Trachea, and Tracheoles. Stigmata are the respiratory openings in a cockroach. These are present on the lateral sides of the body. Trachea and Tracheoles carry oxygen from the diffused air to all parts of the body.

Cells take in oxygen and give out carbon dioxide to the tracheole. Haemolymph the blood of cockroach is involved in the gaseous exchange. between the cells, The carbon dioxide is diffused out through the spiracle openings.

Question 8.
Explain respiration in human beings.
Answer:
Air enters into the nasal cavity through the nostrils. Dust particles present in the air are prevented from entering the lungs. Air passes to the pharynx and then into the trachea. It has ‘C’ shaped rings which prevent it from collapsing.

The trachea is divided into bronchi and into bronchioles and a number of alveoli. Blood circulating around the alveoli gives out CO₂. This oxygenated blood reaches the cells and gives oxygen to the cells and is used for oxidizing glucose. CO₂ formed as a product is carried by the blood to the alveoli and exhaled along the same pathway.

Question 9.
Draw a diagram of the human digestive system label the parts.
Answer:

KSEEB Class 8 Science Chapter 19 Additional Questions & Answers

Question 1.
What are autotrophs?
Answer:
The organisms which prepare their own food are called autotrophs.
Example: Green plants

Question 2.
What is photosynthesis?
Answer:
The process by which the green plants manufacture Organic Compound by using CO₂ and H₂O in the presence of sunlight and Chlorophyll.

Question 3.
What are Stomata?
Answer:
The minute Opening on the leaf Surface is called Stomata.

Question 4.
Draw a neat diagram of the cross-section of the leaf.
Answer:

Question 5.
Mention the two phases of photosynthesis
Answer:
The two phases of photosynthesis are

1. Light reaction
2. Dark reaction (Light independent reaction)

Question 6.
Draw a neat labelled diagram of Chloroplast
Answer:

Question 7.
What arc insectivorous plants? Give example.
Answer:
photo Synthetic plants which are growing in the soil, poor in nitrogen content try to obtain nitrogen by trapping and digesting insects are Called insectivorous plants.
Example: Rosecrans, Nepenthes.

Question 8.
What are epiphytes? Give example.
Answer:
Some plants Capable of photosynthesis take shelter in the host tree Such plants are Called epiphytes
Example: Orchids.

Question 9.
What are Saprophytes? Give example.
Answer:
The organism which obtains Food From dead and decaying organic matter by decomposing the Same is Called as Saprophytes
Example: bacteria, Fungi

Question 10.
What is the benefit of E-Coli bacteria in a man?
Answer:
E – Coli bacteria present in the intestine of man provide the Vital B – Complex Vitamins.

Question 11.
Define the term Symbiosis/ mutual-ism.
Answer:
The mode of nutrition in which two organisms live together and are mutually benefited is called mutual-ism or Symbiosis.

Question 12.
Mention the steps involved in Horologic nutrition.
Answer:
The Horologic nutrition involves Five steps namely

1. ingestion
2. digestion
3. absorption
4. assimilation and
5. egestion.

Question 13.
Define the following terms.

1. Ingestion
2.  Digestion
3.  Absorption
4. Assimilation
5. Egestion.

Answer:

1. Ingestion: The process of taking the Food is called ingestion.
2. Digestion: Conversion of Complex larger molecules into simple smaller molecules by the action of enzymes for easy absorption is called digestion.
3. Absorption: Taking in of Soluble digested nutrients into the blood is called absorption.
4. Assimilation: The process of converting the digested food into protoplasm I.e storing or utilizing in the ells is called assimilation.
5. Egestion: Elimination of undigested Food From the animal body is called egestion.

Question 14.
Explain the nutrition in Amoeba.
Answer:
Amoeba feeds on bacteria, diatoms, unicellular algae, minute protozoa, and even dead organic matter The pseudopodia help in surrounding and ingesting the prey into Food vacuole Digestive enzymes amylase and pro-tease Secreted in the Food Vacuole digest the carbohydrates and proteins respectively into Simple Forms.

The digested Food is diffused into the cytoplasm and circulates so that all the parts of the receives the nutrients, It is used For all the life activities. The undigested Food is egested with the help of pseudopodia.

Question 15.
What are antennae? Write its Functions.
Answer:
The pair of Feelers in the head region of Cockroach is called antennae. It senses the Food and pushes the Food into the mouth.

Question 16.
Draw a neat labeled diagram to show the digestive System of Cockroach
Answer:

Question 17.
Name the parts of alimentary canal of man.
Answer:
The alimentary Canal in eludes the mouth pharynx esophagus stomach Small intestine, large intestine and anus.

Question 18.
Mention the acid present in the gastric juice Mention its Function.
Answer:
The gastric juice contains hydrochloric acid, It kills the microbes that enters in to the stomach through Food and water.

Question 19.
Name the enzymes present in gastric juice and mention its Function.
Answer:
Enzymes present in gastric Juice are

1. pepsin : convert proteins in to polypeptides
2. Rennin : converts the soluble milk proteins insoluble curds.

Question 20.
Mention the juice produced by the liver and where is, it stored?
Answer:
Bile juice is produced by the liver and it is stored in the gall bladder. Bile juice emulsifies Fats.

Question 21.
Mention the enzymes present in pancreatic juice mention its Function.
Answer:
The pancreatic juice contains two enzymes are

1. Amylase:  diverts Starch into maltose
2. Lipase: Converts fats into simple fats

Question 22.
Mention the enzymes present in intestinal juice, mention its Functions.
Answer:

1. Enzymes present in intestinal juice are Maltose – Converts Maltose into glucose.
2. Sucrose – Converts Cane sugar into glucose
3. Lactate – Converts Milk sugar into glucose
4. Peptidase – Converts Peptidase into amino acids
5. Lipase – converts Fats into fatty acids and glycerol

Question 23.
What are villi?
Answer:
The Finger-like projection of the Small intestine which absorbs the digested Food are called villi

Question 24.
What is respiration? Name the two types of Respiration.
Answer:
Respiration is a process by which energy is liberated by oxidation of Food.

1. Aerobic respiration
2. Anaerobic respiration

Question 25.
Differentiate between aerobic and anaerobic respiration.
Answer:

1. Aerobic respiration:
   • oxygen is used to break down organic CO₂ and H₂O
   • A large amount of energy is liberated
   • Occurs in higher Forms of organisms
   • Glucose + Oxygen + Carbon dioxide + water + energy.
   • C₆H₂O₆ + O₂ → 6CO₂+ 6H₂O+ H₂O + Energy.
2. Anaerobic respiration
   • organic compounds are broken in the absence of oxygen, producing alcohol and CO₂
   • Small amount of energy is liberated.
   • occurs in lower Forms of organisms.
   • Glucose + Ethos Alcohol + Carbon dioxide + Energy
   • C₆H₂O₆ → 2C₂H₅OH + 2CO₂ + Energy.

Question 26.
What are spiracles?
Answer:
The respiratory openings in Cockroach are called spiracles.

Question 27.
Draw a neat labelled diagram of the Respiratory System of Cockroach.
Answer:

Question 28.
Draw a neat labeled diagram of human Respiratory System.
Answer:

Question 29.
Define the Following.

1. bronchi
2. bronchioles
3. alveoli

Answer:

1. bronchi: Trachea is divided into two branches called the bronchi
2. bronchioles: The bronchi are Further branched, inf to bronchioles.
3. Air sacs: are present at the terminals of bronchioles. These are called alveoli

Question 30.
Green plants are called as auto tropes? Give reason
Answer:
Green plants can prepare their won Food. Hence, they are called autotrophs.

Question 31.
Amoeba is called as an omnivore.
Answer:
Amoeba feeds on bacteria, diatoms, unicellular algae, minute protozoa, and even dead organic matter, there Fore, Amoeba is called an omnivore.

Question 32.
Parasites have haustoria, Give reason.
Answer:
parasites have haustoria to absorb water and minerals From the host plant.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 14 World of Sounds

KSEEB Class 8 Science Chapter 14 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement/ question. Choose the right answer:

Question 1.
Imagine that you are listening to a popular song from a radio. Using volume control knob, you slightly increase the volume. The factor related to sound wave in this process is increase in.
a. frequency
b. velocity
c. amplitude
d. both frequency and wavelength
Answer:
c. amplitude

Question 2.
The velocity of sound is highest in.
a. air
b. water
c. glass
d. vacuum
Answer:
c. glass

Question 3.
In an unoccupied hall of a choultry you will experience the echo effect of sound. If the same hall is furnished with almirahs, tables, chairs and other commodities, you may not experience the echo clearly It is because,
a. Sound waves get absorbed by the objects in the hall
b. the are of reflecting surface decreases
c. reflected sound is reflected again
d. sound does not get reflected
Answer:
a. sound waves get absorbed by the objects in the hall.

Question 4.
The factor that is transmitted in wave motion is.
a. particles of the medium
b. vibrations of particles
c. energy of the cause of the wave
d. electrons of the medium
Answer:
a. particles of the medium

II. Fill in the blanks with suitable words:

Question 1.
The product of frequency and wave length of a sound waves is called ………..
Answer:
velocity

Question 2.
The SI unit of wave length is ………….
Answer:
Lambda

Question 3.
The velocity of sound in air at 25°C is approximately …………..
Answer:
346 m/sec

III. Answer the following :

Question 1.
Why is sound a longitudinal wave?
Answer:
Sound is a longitudinal wave because it is a mechanical wave in which the vibration of particles is parallel to the direction of the sound.

Question 2.
Explain an activity to show that sound can do work.
Answer:
Take a thin strip of paper. Hold it against sound from a loud speaker the paper starts moving. This shows that sound can do work.

Question 3.
Describe an activity to show that the sound is produced by vibration of materials.
Answer:
Take a rubber string stretch it tightly between two supports. Pluck the string, the string begins to vibrate. Then we will be able to heard some sound, stop the movement of the string. Even the sound also stops. From this activity we can show that the sound is produced by the vibration of material.

Question 4.
Make a list of five musical instrument, state how each of them produce sound.
Answer:

Musical instrument	The way it produce sound
1 .Harmonium	By the vibration of air
2.Tabla	By the vibration of the membrane
3.Sitar	By the vibration of string
4.Guitar	By the vibration of string
5. Flute	By the vibration of air

Question 5.
List two applications of reflection of sound.
Answer:

1. Ultrasound scanner: This is an invaluable diagnostic tool for examining fluid-filled organs such as bladders, kidneys, etc
2. Eco-ranging: By using an ultrasound signal sent by soar and knowing the velocity of sound in water the depth of the sea can be calculated.

Question 6.
Describe an activity that the sound requires a material medium for its propagation.
Answer:

Suspend a mobile phone inside an airtight glass bell jar as shown in the diagram connect the bell to a vacuum pump, when a call is made to that phone, the ringing tone is heard. Start removing the air from the jar by using a vacuum pump. The ringing tone feeble and feeble and cannot hear anymore. This experiment shows that sound cannot travel in a vacuum, it needs a material medium for its propagation.

Question 7.
Represent a wave graphically. Show in the diagram, the wavelength, and amplitude.
Answer:

Question 8.
Why is sound both a boon and a bone?
Answer:
A pleasant sound like Hello sir/Hello madam while addressing a person or hearing musical notes are boon and a loud sound may cause irritation, headache and loss of concentration. Long exposure to such sounds may lead to loss of sleep, tension and stress, high blood pressure, heart trouble etc. Therefore such sounds are bone to us.

Question 9.
What measures would you take to minimize the sound disturbance caused to others?
Answer:
The steps to be taken to minimize the sound disturbance are as follows

1. Turn off your electronic systems. When not in use and also to not play them too loudly
2. Soundproof your music playing area.
3. Plant more trees.
4. Regular maintenance of vehicles and machines.
5. Use earplugs.

KSEEB Class 8 Science Chapter 13 Additional Questions & Answers

Question 1.
What is sound?
Answer:
Sound is a form of energy which excites in our ears the sensation of hearing.

Question 2.
What produces sound?
Answer:
Sound is produced by a vibrating object.

Question 3.
When do materials produce sound?
Answer:
Materials generally produce sound when they move back and forth rapidly. We call such motion as ‘Vibration’

Question 4.
How is the sound produced in the Human body?
Answer:
We have a special apparatus called Larynx or voice box which is located at the upper end of the windpipe. There are two membranes called vocal cords which stretch across the larynx. The narrow slit loft between them controls the passage of air. When we push the air through the slit causes the vocal cords to vibrate which produces the sound.

Question 5.
What are the waves?
Answer:
Any energy moves through a medium by creating a disturbance in it. These disturbances may repeat themselves at regular intervals. Such periodic disturbances constitute a pattern, are called waves.

Question 6.
What are the transverse waves?
Answer:
Transverse waves are the waves, on which the particles of the medium vibrate perpendicularly to the line of propagation.
Ex: water waves.

Question 7.
How do Dolphins and whales live in water communicate?
Answer:
Dolphins and whales produce and use different kinds of sounds and whistles. These sounds travel through water and pass on messages to others. Some species of dolphins send special sounds to identify themselves.

Question 8.
What is meant by wavelength?
Answer:
The distance between two successive compressions is called the wavelength of the sound wave. This is equal to the distance between two successive rarefaction. The wavelength is represented by Lambda (‘A’)

Question 9.
What is the frequency? Explain.
Answer:
The number of times an object vibrates in on second is called Frequency. The number of compressions that pass through a point in one second also gives Frequency SI unit of Frequency is ‘hertz’.
The symbol is Hz.  1 hertz (Hz) = 1 wave per second or cycle per second.

Question 10.
What is meant by the amplitude of a sound wave?
Answer:
The highest displacement of a particle from its rest position is the amplitude of the sound.

Question 11.
What is an Amplifier?
Answer:
Amplifier is a device that increases the amplitude of a wave.

Question 12.
What is the speed of sound?
Answer:
Speed of sound is the distance traveled by it in one second. The SI unit of speed is meter per second we write this as ms^-1.

Question 13.
What is meant by the Echo?
Answer:
The reflection of sound is called Echo.

Question 14.
What do you mean by Sonic boom?
Answer:
When a plane travels faster than the speed of sound the plane breaks the sound barrier and produces a loud sound. This is called the Sonic boom.

Question 15.
Does the experiment show that sound reflects?
Answer:

There are two identical cardboard tubes P and Q with metal surface AB and screen S between the two tubes as shown in the figure. Keep a small clock at the other end of the tube ‘P’ and ear at the end of the tube Q. The tick-tick of the clock can be heard if the angle is the same.

Question 16.
What is meant by Noise?
Answer:
Some sound cause disturbance to humans and other animals, such unwanted sound is called Noise, or Unpleasant sound is called Noise [High-frequency sound].

Question 17.
Mention the harmful effects of noise pollution.
Answer:
Unwanted sound leads to noise pollution.
Effects of noise pollution.

1. 1. Loud sound may cause irritation, headache, and loss of concentration.
   2. Long exposure to such sounds may lead to loss of sleep, tension, and stress

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 10 Energy and its Forms

KSEEB Class 8 Science Chapter 10 Textual Questions & Answers

I. Four alternative are given to each of the following incomplete statement/ question. Choose the right answer :

Question 1.
The type of energy that can be easily converted into other forms is.
a) sound
b) light
c) heat
d) electricity
Answer:
d) electricity

Question 2.
Kinetic energy present in the following is.
a) water stored in a dam
b) stretched rubber band
c) water released from a dam
d) compressed spring
Answer:
c) water released from a dam

Question 3.
The correct formula to find the velocity of a body with kinetic energy ‘K’ is.
a) \(\mathrm{v}=\frac{2 \mathrm{k}}{\mathrm{m}}\)
b) \(v=\sqrt{\frac{2 k}{m}}\)
c) \(\mathrm{v}=\frac{4 \mathrm{k}^{2}}{\mathrm{m}}\)
d) \(v=\frac{1}{2} k m\)
Answer:
b) \(v=\sqrt{\frac{2 k}{m}}\)

Question 4.
The correct sequence of energy changes in hydroelectric power station is.
a) kinetic to potential, to mechanical to electrical
b) potential to kinetic to mechanical to electrical
c) potential to electrical to mechanical
d) potential to electrical to kinetic to mechanical
Answer:
b) potential to kinetic to mechanical to electrical

Question 5.
Which of the following object has higher potential energy?
a) mass = 10 kg, g = 9.8 ms^-2, h = 10 m
b) mass = 5 kg, g = 9.8 ms^-2, h = 12 m
c) mass = 8 kg, g = 9.8 ms^-2, h = 100 m
d) mass = 6 kg, g = 9.8 ms^-2, h = 20 m
Answer:
c) mass = 8 kg, g = 9.8 ms^-2, h = 100 m

II. Fill in the blanks with suitable words

Question 1.
Unit of power is …………
Answer:
watt

Question 2.
Unit of energy is ………….
Answer:
joule

Question 3.
If a candle is burnt the chemical energy is transformed into …………..
Answer:
light and heat energy

Question 4.
The water stored in an overhead tank possesses ……….. energy
Answer:
potential energy

Question 5.
In a cinema theater electrical energy is transformed in to ………… and ………… energy
Answer:
light and sound

III. Answer the following:

Question 1.
State whether the energy possed in the following is kinetic or potential.

1. compressed spring
2. stretched bow
3. moving arrow
4. water stored in a dam
5. a stone at the top of the building
6. bird resting on the branch of a tree

Answer:

1. potential energy
2. potential energy
3. kinetic energy
4. potential energy
5. potential energy
6. potential energy

Question 2.
Distinguish between potential energy and kinetic energy.
Answer:

1. Kinetic energy
   • The energy that the body possesses due to its motion.
   • It depends on the mass of the body and velocity with which it is moving kinetic energy = 1/2 mv²
2. Potential energy
   • The energy which a body possesses either due to its position or due to its deformation.
   • It depends on mass of the body and height to which it is raised from ground
   • The potential energy = m × g × h

Question 3.
A bus and a car are moving at the same speed. Which of the two has greater kinetic energy.
Answer:
The bus has greater kinetic energy since it has got greater mass than car. even though they are moving with the same speed.

Question 4.
A ball of mass 200 grams falls from height of 5 meter ? What is its kinetic energy when it just reaches the ground ?
(g = 9.18 ms^-2)
Answer:
m = 200 grams = 0.2 kg
h = 5 m
u = 0
v = 7
Solution:
v² – u² = 2gh
v²– 0² = 2 x 9.8 x 5
v² = 98
kinetic energy, KE = \(\frac{1}{2} m v^{2}\)
\(\frac { 1 }{ 2 }\) × \(\frac { 200 }{ 1000 }\) × 98 = 9.8 joule

Question 5.
There are a number of devices in common use that change energy from one form to another, Name some devices that change

1. electrical energy into light energy
2. electrical energy into mechanical energy
3. electrical energy into heat
4. sound energy into electrical energy
5. chemical energy into electrical energy

Answer:

1. electric bulb
2. motor
3. electric heater
4. microphone
5. electric cell

Question 6.
Describe the mode of energy trans. formation in a mechanical and quartz clock.
Answer:
In a mechanical clock, the spring is compressed by winding, it attains potential energy. The releasing of the spring slowly is the kinetic energy, using that the wheels of the clock turn, therefore potential energy is converted into kinetic energy. PE → KE → mechanical energy.

In the quartz clock, the electric cell gives, the electrical energy and it is converted into mechanical energy by which the wheels of the clock turns. Therefore the energy transformation is chemical energy → electrical energy → mechanical energy.

Question 7.
What kind of energy transformation takes place at the thermal power station?
Answer:
In a thermal power station, coal is used to generate heat and water is boiled, the resulting steam is used to drive the turbine which is connected to a generator, so the energy transformation at the thermal power station can be written as. Chemical energy → heat energy → mechanical energy → electrical energy.

KSEEB Class 8 Science Chapter 9 Additional Questions & Answers

Question 1.
What is work? Mention the factors on which the work done by a force depends on?
Answer:
Work is said to be done when the point of application of a force moves.
W = F x d
The work done by the force on a body depends on two factors.

1. Magnitude of the force and
2. distance that the body moves

Question 2.
How is work done measured?
Answer:
Work done by moving a body is equal to the product of force exerted on the body and the distance moved by the body in the direction of the force.
i.e, work = force x distance

Question 3.
Write the unit of work.
Answer:
Work done by moving body is equal to the product of force exerted on the body and the distance moved by the body in the direction of a force. Work = Force x Distance moved in the direction of force.

Question 4.
Define Joule
Answer:
Joule can be defined as when a force of on newton moves a body through a distance of one meter in its own direction.

Question 5
What is energy crisis?
Answer:
If the demand for energy is more than 1 the supply then it leads to energy crisis.

Question 6.
Name the types of mechanical energy.
Answer:
The two forms of mechanical energy are

1. Potential energy and
2. Kinetic energy

Question 7.
What is kinetic energy? Mention the factors that the kinetic energy of a body depends.
Answer:
The energy possessed a body by virtue of its motion is called kinetic energy. KE = 1/2 mv²
Kinetic energy depends on

1. the mass of the body and
2. velocity with which it is moving

Question 8.
What is potential energy? Mention the factors that the potential energy of a body depends.
Answer:
The energy which a body possesses either due to its position or due to its deformation is called potential energy.
PE = m × g × h
The potential energy of a body depends on

1. the mass of a body and
2. the height to which it is raised from the ground.

Question 9.
Give example for the potential energy.
Answer:
A stretched rubber band, Mangoes in the tree, water stored in the dam, stretched bow pressed spring stretched sling of a catapult.

Question 10.
Give example for the kinetic energy.
Answer:
The moving air, the moving ball, the flowing water, the moving Striker.

Question 11.
A car is moving with a uniform velocity of 15 ms^-1 What is the kinetic energy of a boy of mass 40 kg sitting in the car?
Answer:
m = 40 kg
v = 15 ms^-1
KE = ?
Solution :
Velocity of the boy = velocity of the car kinetic energy possessed by the boy
\(=\frac{1}{2} \mathrm{mv}^{2},=\frac{1}{2} \times 40 \mathrm{kg} \times\left(15 \mathrm{ms}^{-1}\right)^{2}=4500 \mathrm{J}\)

Question 12.
If two bodies of equal masses move with a uniform velocity of‘v’ and ‘3v what will be the ratio of their kinetic energies?
Answer:
Mass of first body = m
Velocity of the first body = v
mass of second body = m
velocity of second body = 3v
The ratio of the kinetic energy of the two bodies

The ratio of the kinetic energy  of the bodies = 1:9

Question 13.
A bag of wheat weighs 200 kg to what height should it be raised so that its potential energy is 9800 joule (g = 9.8 ms²)
Answer:
m = 200 kg
g = 9.8 ms²
PE = 9800 J
PE = m × g × h
9800 J = 200 kg x 9.8 ms^-2 x h
h = 9800
J = 200 kg x 9.8 ms^-2
h = 5 m
Thus, the bag of wheat should be raised to a height of 5 m.

Question 15.
What is power?
Answer:
The rate of doing work.
power = \(\frac{\text { Work }}{\text { time }}\)
The unit of power is called Watt.
1 kilowatt = 1000 w.
The unit or power is called Watt.
1kilowatt = 1000 w.

Question 16.
A body does 20 joules of work in 5 seconds. What is its power?
Answer:
W = 20 j
t = 5 seconds
P = 4 w
P = \(\frac{W}{t}\)
P = \(\frac{20}{5}\) = 4 W
P = 4 W

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 13 Water

KSEEB Class 8 Science Chapter 13 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement/questions. Choose the right answer.

Question 1.
Magnesium sulfate crystals are commonly called …………..
a) Gypsum salt
b) Epsom slat
c) green vitriol
d) Alum
Answer:
b) Epsom slat

Question 2.
When you buy washing soda from the market, you will get it in powder form because ………….
a) The crystals of washing soda quickly lose water molecule
b) The shop keeper prefers to power the crystal.
c) washing soda does not form crystals
d) washing soda is a drying agent
Answer:
a) The crystals of washing soda quickly lose water molecule

Question 3.
A sample of hard water is heated in a utensil a white deposit of calcium carbonate is formed. This is due to the presence of ….
a) calcium chloride
b) magnesium sulfate
c) calcium bicarbonate
d) calcium hydroxide
Answer:
c) calcium bicarbonate

Question 4.
The salt that cause hardness in water and that liberates carbon dioxide on heating is
a) magnesium bicarbonate
b) calcium chloride
c) magnesium sulfate
d) calcium sulfate
Answer:
a) magnesium bicarbonate

Question 5.
When steam is passed over red hot …………. iron we get the following products
a) Ferric hydroxide and hydrogen
b) Ferric oxide and hydrogen
c) Ferrous hydroxide and hydrogen
d) Ferrous ferric oxide and hydrogen
Answer:
d) Ferrous ferric oxide and hydrogen

II. Fill in blanks with suitable words :

Question 1.
The chemical name of Epsom salt is ………..
Answer:
sulfate (Magnesium)

Question 2.
The chemical used to soften hard water is …………..
Answer:
sodium carbonate

III. Match the following :

Answer:

1. d
2. a
3. b
4. c

IV. Answer the following:

Question 1.
Water is tasteless, but we experience different tastes of water in different places. Why?
Answer:
Water obtained from different places has several salts dissolved in it, therefore, water has different taste even though pure water is tasteless.

Question 2.
Write the balanced equations for the reaction of sodium, potassium and calcium on cold water.
Answer:

1. 2Na + 2H₂O → 2NaOH + H₂ ↑
2. 2K + 2H₂O → 2 KOH + H₂ ↑
3. Ca + 2H₂O → Ca(OH)₂ + H₂ ↑

Question 3.
What happens When steam is passed over red hot iron? Write the equation.
Answer:
When steam is passed over red hot iron hydrogen is liberated along with the formation of ferric oxide.
3Fe + 4H₂O → Fe ↑ + 4H₂

Question 4.
Define the terms efflorescence and Deliquescent.
Answer:

1. Efflorescence: Certain hydrates lose water when exposed to air of moderate humidity are called substances.
2. Deliquescence: Certain water-soluble substances, when exposed to the atmosphere at ordinary temperature, absorb moisture from the atmospheric air to become moist and ultimately dissolved in the absorbed water. Such substances are called deliquescent substances.

Question 5.
Give two reasons to prove that water is a compound and not an element.
Answer:
Though water contains combustible hydrogen and supporter of combustion oxygen, water is neither a supporter of combustion nor a combustible substance. Water has a different property which hydrogen and oxygen do not have i.e., it is a very good fire extinguisher, compound does not show the properties of elements by which it is formed but it will have a different property since it is a new substance. By this one can prove that water is a compound.

Question 6.
Name three metals which do not react with water under normal conditions.
Answer:
Copper, tin and aluminium are the three metals which do not react with water under normal conditions.

Question 7.
Name the products formed when the following oxides are dissolved in water. Write balance of equation.

1. Sulfur dioxide
2. potassium oxide
3. calcium oxide
4. Carbon dioxide

Answer:

1. When sulfur dioxide dissolves in water sulfurous acid is formed.
   SO₂ + H₂O → H₂SO₃
2. When potassium oxide dissolves in water-potassium hydroxide is formed
   KO + H₂O → KOH
3. When calcium oxide dissolves in water calcium hydroxide is formed.
   CaO +H₂O → Ca(OH)₂
4. When carbon dioxide dissolves in water carbonic acid is formed.
   CO₂+ H₂O → H₂CO₃

Question 8.
State the reasons for hardness in water.
Answer:
Presence of water soluble calcium and magnesium bicarbonate sulfates and chlorides cause hardness in water.

V. Give reasons for the following :

Question 1.
Sodium metal should be stored under Kerosene.
Answer:
Sodium is to be kept under kerosene as it can react with oxygen and water vapors present in air and kerosene has no affinity towards sodium.

Question 2.
Washing soda loses its crystal structure quickly.
Answer:
Washing soda loses its crystal structure quickly as it loses water when exposed to air of moderate humidity. It is efflorescent substance.

Question 3.
When calcium nitrate crystals are exposed to air a solution is formed?
Answer:
Calcium nitrate when exposed to air absorb moisture from the atmospheric air to become moist and dissolve in the absorbed water therefore it cannot be in the crystal form. It is deliquescent substance.

KSEEB Class 8 Science Chapter 13 Additional Questions & Answers

Question 1.
Explain the biological significance of water.
Answer:
Water is one of the most abundant and important compounds in the world. It is the major constituent of all living organism, some plants contain more percentage of water, the human body has about 65% of water. Neither plants, animals nor human beings can survive without water.

Question 2.
Water is called the universal solvent. Why?
Answer:
Water is called the universal solvent because it dissolves more substance than any other solvent.

Question 3.
What is the chemical formula of water?
Answer:
The chemical formula of water is H₂O

Question 4.
Write the molecular structure of water molecule
Answer:

Question 5.
Many metals and their alloys are used to prepare utensils why?
Answer:
Many metals and their alloys are used to prepare utensils because they do not react with water under normal conditions.

Question 6.
What happens when potassium is dipped in water?
Answer:
When potassium is dipped in water forming respective hydroxides liberating hydrogen gas.

Question 7.
What happens when sodium is dipped in water?
Answer:
Sodium piece rushes here and there reacting with water violently. It gradually diminishes in size and finally disappears. It dissolves in water forming sodium hydroxide and hydrogen.

Question 8.
Write the equation for the reaction between potassium and water.
Answer:
2k + 2H₂O →  2kOH + H₂ ↑

Question 9.
Rusting is quick in rainy season why?
Answer:
Rusting is quick in the rainy season because the humidity will be more in the rainy season, which promotes rusting..

Question 10.
What happens when steam is passed over red hot metals like zinc, iron, magnesium. Write a balanced equation.
Answer:
When steam is passed over red hot metals like zinc, iron, magnesium we get respective oxides and hydrogen gas.
Zn + H₂O → ZnO+ H₂ ↑
3Fe + 4H₂O → Fe₃O₄ + 4H₂O ↑
Mg + H₂O →  MgO+H₂ ↑

Question 11.
What happens when steam is passed over red hot coke and silicon.
Answer:

1. When steam is passed over red hot coke, a mixture of carbon monoxide and hydrogen is formed.”
   C + H₂O → CO ↑ + H₂↑
2. When steam is passed over red hot silicon, which is a non-metal silicon dioxide and hydrogen gas are formed.
   Si + 2H₂O → SiO₂  +2H₂  ↑

Question 12.
What happens when carbon dioxide dissolves in water.
Answer:
When carbon dioxide dissolves in water carbonic acid is formed.
CO₂  + H₂O → H₂CO₃ (Carbonic acid) Carbonic acid is present in soft drinks.

Question 13.
What happens when calcium oxide reacts with water. Write a balanced equation.
Answer:
When calcium oxide reacts with water it forms calcium hydroxide
CaO + H₂O → Ca(OH)₂ 

Question 14.
Give some examples of the substances which can absorb moisture.
Answer:
The substances which absorb moisture are magnesium chloride, solid sodium hydroxide, solid potassium hydroxide, anhydrous calcium chloride, calcium nitrate Ferric chloride, and sodium nitrate.

Question 15.
Define deliquescence.
Answer:
Certain water-soluble substances, when exposed to the atmosphere at ordinary temperature, absorb moisture from the atmospheric air to become moist and ultimately dissolved in the absorbed water. Such substances are called deliquescent substances.

Question 16.
Give some examples of desiccants.
Answer:
Concentrated sulfuric acid and calcium chloride monohydrate are examples for desiccants.

Question 17.
Define Efflorescent substances.
Answer:
Certain hydrates that lose water when exposed to air of moderate humidity are called substances.

Question 18.
Give an example of efflorescent substances.
Answer:
Sodium sulfate, (NaSO₄10H₂O) washing soda (Na₂CO₃H₂O).

Question 19.
Calcium carbonate does not cause hardness. Why?
Answer:
Calcium carbonate does not cause hardness because it is insoluble in water.

Question 20.
Name the salts causing hardness in water.
Answer:
Calcium and magnesium bicarbonates, sulfates, and chlorides cause hardness in water.

Question 21.
What is meant by hard water?
Answer:
The water which does not give lather with soap is called hard water.

Question 22.
What is meant by soft water?
Answer:
The water which gives lather readily with soap is called soft water.

Question 23.
Why is hard water not used in industrial boilers?
Answer:
Hard water contains calcium and magnesium soluble salts. If it is used in industrial boilers, it forms insoluble salts of calcium and magnesium. They produce scales on the inner walls of the boilers, which reduce heating efficiency. There is a chance of an explosion of boilers due to foaming. It also corrodes the boilers.

Question 24.
Mention methods of removal of hardness of the water.
Answer:
Hardness can be removed by two methods.

1. If hard water contains only magnesium and calcium bicarbonate it can be made soft by boiling. In this reaction, bicarbonates are converted into insoluble carbonate and CO₂
   Ca (HCO₃)₂ → CaCO₃ + H₂O + CO₂↑
   Mg (HCO₃)₂ → MgCO₃+ H₂O + CO₂↑
2.  Hardness can be removed by the addition of washing soda to water. In this reaction, the soluble salts of calcium and magnesium are converted into insoluble carbonates. The soluble sodium salts do not cause hardness.
   CaCl₂+ Na₂CO₃  → CaCO₃ + 2NaCl  ↓
   CaHCO₃ +Na₂CO₃ → CaCO₃↓ + 2NaHCO₃
   CaSO₄ + Na₂CO₃ → CaCO + Na₂SO₄

Question 25.
Experiment to show the removal of hardness by washing soda.
Answer:
Materials required:

1. beaker
2. glass rod
3. washing soda
4. hard water

Take some hard water in a beaker, and add a small quantity of washing soda to it stir it with a glass rod. Allow the insoluble carbonates to settle down or precipitate. Filter or decant the liquid. Water so obtained is soft water. But it is unfit for drinking as it contains an excess of washing soda and excess of sodium salts.

Question 26.
What is meant by Desalinization?
Answer:
Desalinization is an artificial process by which saline water (generally seawater) is converted into freshwater.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 23 Earth and Beyond

KSEEB Class 8 Science Chapter 23 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement/ questions. Choose the right answer.

Question 1.
The constellation that helps to locate north star is.
(a) Cassiopeia
(b) Orion
(c) Taurus
(d) Leo
Answer:
(a) Cassiopeia

Question 2.
The second biggest planet of the solar system has.
(a) lowest density
(b) density equal to water
(c) highest density
(d) density equal to earth.
Answer:
(a) lowest density

Question 3.
The poles of this planet faces the sun for longer periods of time than any other planet.
(a) Mars
(b) Uranus
(c) Jupiter
(d) Saturn
Answer:
(a) Mars

Question 4.
Polar ice caps of the planet mars are due to.
(a) Solidified water
(b) solidified carbon dioxide
(c) volcanoes erupted near the poles
(d) cover of dust particles that reflect
Answer:
(b) solidified carbon dioxide

Question 5.
Heatwaves are trapped to the maximum extent in the planet.
(a) Mercury
(b) Venus
(c) Earth
(d) Neptune
Answer:
(b) Venus

II. Fill in the blanks with suitable words:

Question 1.
Radio signals are emitted by the planet ………….
Answer:
Jupiter

Question 2.
The color of the planet Mars is ………….
Answer:
Reddish

Question 3.
Winter season constellation is ………….
Answer:
Orion

Question 4.
Asteroids are mainly found between the orbits of ………..
Answer:
Mars and Jupiter

Question 5.
Ultraviolet rays from the sun can be filtered by the earth’s atmospheric layer called …………
Answer:
Ozone layer present in the upper regions of the Stratosphere.

III. Match the following:

Answer:

1. (e)
2. (d)
3. (f)
4. (a)

IV. Answer the following:

Question 1.
Which planet is called morning star or evening star?
Answer:
Venus.

Question 2.
Which planet was removed from the list of 9 planets in 2006?
Answer:
Pluto.

Question 3.
Express the following in km.

1. 10 light minutes
2. 10 light days
3. 10 Light year

Answer:

1. light minutes
   10 × 60 × 300000 = 180000000 km = 180 million km
2. 10 light days
   10 × 24 × 60 × 60 × 300000 = 259300000000 km = 259200 million km
3. 10 light years
   10 × 365 × 24 × 60 × 60 × 300000 = 94608000000000 = 94608000 million km

Question 4.
Name the following:

1.  Most fascinating planet with a set of ring systems as viewed from a telescope.
2.  Nearest planet to earth.
3.  Nearest planet to the sun
4.  Biggest planet of the solar system

Answer:

1. Saturn
2. Venus
3. Mercury
4. Jupiter

Question 5.
How are satellites different from planets?
Answer:
Planets:

1. planets are natural celestial objects
2. planets revolve round the sun
3. planets are big in size Satellites:
4. Satellites may be natural or artificial objects.
5. Satellites revolve round the planets.
6. Satellites are smaller in size than planets.

Question 6.
Which satellite has active volcanoes?
Answer:
In a satellite of Jupiter has active volcanoes.

Question 7.
Give a reason for the following.
Answer:

1. A person in England can recognize the pole star easily than a person in Bangalore: Pole star appears to be stationary above the Earth’s North Pole since England lies in the Northern side Northern hemisphere a person in England can recognize pole star than a person in Bangalore.
2. Mercury in difficult to observe: It is very difficult to observe mercury because it is very close to the sun and most the time it is hidden by the glare of the sun. However, it can be seen just before sunrise and just after sunset.
3. A day on Venus is longer than its year: The period of rotation of Venus is 243 days and the period of revolution is 224 days. Since the period of rotation is longer than a period of revolution, a day on Venus is longer than its year.
4. The greenhouse effect is prominent on Venus: Venus is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. This dense atmosphere of carbon-dioxide blocks the long-wavelength infrared radiation and heat is trapped inside, hence the greenhouse effect is prominent on Venus.

V. State true or false:

Question 1.
Saturn has the highest density.
Answer:
False

Question 2.
Venus can be seen overhead in the night sky.
Answer:
False

Question 3.
Aries (Mesha) is zodiacal constellations.
Answer:
True

Question 4.
Mars contains oxygen in its atmosphere.
Answer:
True

Question 5.
Moon has no atmosphere.
Answer:
True

Question 6.
Titan is the satellite of Jupiter.
Answer:
False

KSEEB Class 8 Science Chapter 23 Additional Questions & Answers

Question 1.
Define the following terms

1. celestial objects
2. celestial sphere
3. horizon

Answer:

1. celestial objects: The objects in the sky are called celestial objects.
2. celestial sphere: The imaginary sphere centered around us is called the celestial sphere.
3. horizon: The imaginary circle along which the sky appears to meet the ground is called the horizon.

Question 2.
Write the differences between the geocentric model and the heliocentric model.
Answer:

1. Geocentric model:
   • Earth is considered the center of the universe.
   • all other celestial objects move around the earth.
   • This model scientifically not accepted.
   • It was not possible to explain many events like solar eclipses and the variation in the path of planets.
2. Heliocentric model:
   • Sun is at the center of the observable universe.
   • All other celestial objects including the earth move around the sun.
   • Kepler and Galileo provided scientific evidence.
   • Possible to explain the events like solar eclipses and gravitational laws helped in better undering of Heliocentric model.

Question 3.
Explain our solar system?
Answer:
Our solar system comprises of the following:

1. The sun which is the center of the solar system.
2. Eight planets are mercury, Venus, Earth, mars, Jupiter, saturnuranus and Neptune,
3. The Asteroid belt between the orbits of mars and Jupiter
4. Satellites of the planets, which are also Called the moons of the planets.
5. Comets such as Halley.
6. Artificial Satellites and space crafts,

Question 4.
What is meant by light year?
Answer:
The light year is the distance traveled by light in one year, traveling at the speed of 3,00,00 Km/S through Vacuum.

Question 5.
What is  meant by period of rotation
Answer:
The time taken by a planet or a satellite to rotate once around its own axis is called period of rotation.

Question 6.
What is meant by period of revolution.
Answer:
The Time taken by a member of solar system to go around the sum once is called period of revolution.

Question 7.
What factors made us to think about the existence of some form of life in mars?
Answer:
Some places in mars hove moderate range of temperature, It has Oxygen, nitrogen and water It has Frozen Carbon dioxide near the poles factors that mode us to think about the existence of some Formic of life on mars.

Question 8.
What are asteroids?
Answer:
Thousands of irregular Shaped lumps of rocks that orbit the sun are called asteroids,

Question 9.
Name Some of the largest asteroids.
Answer:
Ceres, pallas, Juno and Vesta are the some largest asteroids.

Question 10.
What are Meteoroids?
Answer:
Meteoroids are the Chunks of matter which may originate from asteroid belt that may enter the earth’s atmosphere and burn due to neat generated by Friction.

Question 11.
What are meters?
Answer:
The meteoroids which bum completely are called meteors and also called as Shooting stars or Falling Stars

Question 12.
What are Meteorites?
Answer:
The Bigger meteorites Sometimes Survive the Journey and hit the earth Surface resulting Craters and vent on the earth’s crust they are called as meteorites.

Question 13.
Which is the biggest planet of the solar system.
Answer:
Jupiter is the biggest planet of the solar system.

Question 14.
Name the Galilean Satellites.
Answer:
Io, Europa, Ganymede, and Callisto are the Four satellites identified by Galileo.

Question 15.
What are comets?
Answer:
Comets are considered as the guests of the solar system made up of silicates and frozen gases, and dust which have a very long orbital period and appear rarely

Question 16.
Name the Second biggest planet of the solar system.
Answer:
Saturn’s The second biggest planet of the solar system, Its special feature is permanent ring system.

Question 17.
What are constellations?
Answer:
The region around recognizable pattern of a group of stars is called Constellation.

Question 18.
What are Zodiacal constellation?
Answer:
The 12 Constellation which is located in the Zodiacal belt is called Zodiacal constellation.

Question 19.
What is meant by the zodiac belt?
Answer:
The movement of the sun, the planets, and the moon appear to Follow a path From east, to west This apparent path is called zodiac belt.

Question 20.
Name the zodiacal constellations
Answer:

1. Aries (Mesha)
2. Tautds (Vrishabha)
3. Gemini (Mithuna)
4. Cancer (Karka)
5. Leo(Somha)
6. Virgo (Kanya)
7. Libra (tula)
8. Scorpius (vrischika)
9. Sagittarius (Dhanu)
10. Capri cornus (Makara)
11. Aquarius (Kumbha)
12. Pisces (Meera)

Question 21.
Stars appear small even they arc very large, Give reason.
Answer:
Stars appear very Small because they are far away from the earth.

Question 22.
Saturn Can plot on water Give reason.
Answer:
The specific gravity of Saturn is (0,13) less than that of water hence it can Float on water

Question 23.
Why do comets develop tails as they approach the sun?
Answer:
Comets are silicates and matter made up of frozen gases. As they approach the sun, their frozen gases gradually vaporize. The energetic particles produced by the sun push the gases away leading to the formation of tail.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 17 Our Colourful World

KSEEB Class 8 Science Chapter 17 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statements questions. Choose the right answer.

Question 1.
Rearview mirror of motor vehicles contain
(a) plain mirror
(b) convex mirror
(c) concave mirror
(d) convex lens
Answer:
(b) convex mirror

Question 2.
If a ray light is traveling from denser medium to rarer medium and if the angle of incidence is greater than the critical angle, the following takes place.
(a) Total Internal
(b) refraction
(c) dispersion
(d) multiple refractions
Answer:
(a) Total Internal

Question 3.
A concave mirror forms magnified inverted image when the object is placed at
(a) F
(b) C
(c) between F and C
(d) beyond C
Answer:
(c) between F and C

Question 4.
On a new stainless steel spoon if you set the image of your face upside down, then that part of the spoon acts like
(a) convex lens
(b) concave mirror
(c) convex mirror
(d) concave lens
Answer:
(b) concave mirror

Question 5.
You can see the image of your face on the surface of still water. But if the water is disturbed your image will not be clear because of
a) total internal reflection
b) refraction
c) irregular reflection
d) dispersion
Answer:
c) irregular reflection

II. Fill in the blanks with suitable words:

Question 1.
The letter ‘P’ looks like ……….. in a plane mirror.
Answer:
q

Question 2.
The type of lens used by watch repairers is ………..
Answer:
convex lens

Question 3.
Bending of light when it passes from one transparent medium to another is called ……….
Answer:
refraction

Question 4.
Formation of the rainbow is due to …………
Answer:
dispersion of light

III. Answer the following

Question 1.
Give one reason to prove that light is a form of energy.
Answer:

1. Plants can carry out photosynthesis with the help of light energy and prepare food. Since light has the ability to do work it is a form of energy.
2. One form of energy can be transferred into other forms. Since photocell can change the light into electrical energy. It is a form of energy.

Question 2.
What is the difference between regular and irregular reflection?
Answer:

Regular reflection	Irregular reflection
1. happens in a perfectly flat surface or     polished surface	1. happens if the reflecting surface is rough
2. image formed will be clear	2. image will not be clear
3.pattern of incident light is present in reflecting  light	3. since the light get scattered the pattern of incident light is not found in reflected light

Question 3.
State the laws of reflection.
Answer:

1.  Angle of incidence is equal to the angle of reflection.
2.  The incident ray, the normal drawn to the mirror at the point of incidence and the reflected ray all lie on the same plane

Question 4.
Mention the uses of a concave mirror.
Answer:
Concave mirrors are used by dentists and in the solar furnace and in the headlight of motor vehicles.

Question 5.
Why is the convex mirror used as a rearview mirror in motor vehicles?
Answer:
Convex mirrors always produce erect diminished virtual images of the objects. The driver gets a clear image of the vehicles coming from behind, therefore it is used as a rearview mirror in motor vehicles.

Question 6.
Mention any two effects of refraction of light in daily life.
Answer:

1. A coin in a cup that is just invisible can be made visible by pouring water in the cup.
2. The bottom of a water tank appears to be raised.

Question 7.
What are the conditions for total internal reflection to take place?
Answer:
The condition for total internal reflection takes place are

1. If the light ray travels from a denser medium to a rarer medium.
2. Angle of incidence must be greater than the critical angle for the two media.

Question 8.
Draw the diagrams to show the refraction of parallel rays of light in

1. convex lens
2. concave lens.

Answer:

Question 9.
Mention any four devices that contain a convex lens.
Answer:
The convex lens is used in a simple microscope, compound microscope, telescope, and also in the spectacles used by the people who have hypermetropia.

Question 11.
What is the dispersion of light?
Answer:
The splitting up of white light into its constituent colors is called dispersion.

IV. Match the following :

Answer:

1. (e)
2. (d)
3. (b)
4. (c)

KSEEB Class 8 Science Chapter 17 Additional Questions & Answers

Question 1.
What is light?
Answer:
Light is a form of energy enable us to see the things

Question 2.
Mention the sources of light.
Answer:
Major source of light is the sun. Light can also be produced with the help of candles bulbs. Fluorescent lamps, gas lamps etc.

Question 3.
Write an experiment to prove the laws of reflection.
Answer:

Keep a white sheet of paper on one side of the hollow box and pin it at the four corners. Make incisions on the box to the size of the cardboard slit and mirror and the cardboard slit perpendicularly in the incisions made, pass light from a torch through the opening of the cardboard slit, in an oblique manners.

We can see light ray getting reflected after striking the mirror. Mow carefully draw lines with the help of pencil to mark the position of the mirror the incident ray and the reflected ray on the paper remove the mirror comb and torch. Draw perpendicular line to the mirror at a point where the incident ray strikes the mirror.

Which is called as normal measure the angle of incidence and angle of reflection. We can find that angle of incidence is equal to the angle of reflection. The incident ray, normal and reflected ray all lie on the same plane.

Question 4.
Mention the characteristic of the image formed by a plane mirror.
Answer:

1. The image is laterally inverted.
2. It is virtual.
3. The image on the plane mirror is erect.
4. The image is as far behind the mirror as the object in front of it.

Question 5.
What is meant by lateral inversion?
Answer:
Lateral inversion means lift of the object will become right of the image and right of the object will become left of the object.

Question 6.
Draw a ray diagram to show the laws of reflection by a plane mirror.
Answer:

Keep a white sheet of paper on one side of the hollow box and pin it at the four corners. Make incisions on the box to the size of the cardboard slit and mirror and the cardboard slit perpendicularly in the incisions made, pass light from a torch through the opening of the cardboard slit, in an oblique manners.

We can see light ray getting reflected after striking the mirror. Mow carefully draw lines with the help of pencil to mark the position of the mirror the incident ray and the reflected ray on the paper remove the mirror comb and torch. Draw perpendicular line to the mirror at a point where the incident ray strikes the mirror.

Which is called as normal measure the angle of incidence and angle of reflection. We can find that angle of incidence is equal to the angle of reflection. The incident ray, normal and reflected ray all lie on the same plane.

Question 7.
What are spherical mirror and mention the types?
Answer:
Spherical mirror is a part of a sphere with polished surface on one of the side.
The two types of spherical mirror are

1. concave mirror
2. convex mirror.

Question 8.
Draw diagrams to show the reflection of parallel rays of light in
1. Concave mirror
2. convex mirror.
Answer:

Question 9.
What is meant by the following terms?

1. Pole of the mirror
2. principal focus
3. focal length
4. center of curvature
5. radius of cunaiure
6. principal axis
7. Object distance
8. image distance.

Answer:

1. Pole of the mirror : pole of the mirror is the center of the reflecting surface. The ray of light along the principal axis  which is incident on the pole of the mirror retraces its path along the principal axis.
2. Principal focus : It is the point of convergence of a parallels beam of light which are also parallel to principal after  reflection. It is denoted by ‘F’.
3. Focal length : The distance between the pole of the mirror and the point of focus reflected parallel rays of light which  are incident on the mirror is called focal length. It is denoted by ‘P’.
4. Center of curvature : It is center of the sphere of which the mirror is a part. It is denoted by ‘C’.
5.  Radius of curvature : The radius of the sphere of which the mirror apart is called radius of curvature it is denoted by ‘V’. the radius of curvature is twice the focal length r = 2 ‘f’
6. Principal axis : The imaginary extended line on which the pole of the mirror, the point of focus and the center of the  curvature are located is called principle axis.
7. Object distance : The distance of the object from the pole of the mirror is called object distance it is denoted by ‘V’.
8. Image distance : The distance between the mirror and the image is called image distance it is denoted by ‘V’.

Question 10.
Write the equation to show the relation among focal length object length and image length.
Answer:
\(\begin{array}{l}{\text { Focal length }=\frac{\text { Product of image distance }}{\text { Sum of image distance }}} \\ {=\frac{\text { and object distance }}{\text { and object distance }}}\end{array}\)

Question 11.
What is refraction?
Answer:
The bending of light when it passes from one transparent medium to another is called refraction.

Question 12.
What happens when a ray of light passes from one transparent medium to another transparent medium?
Answer:
Water is a denser medium than air when an oblique ray of light travels from rarer medium to denser medium it bends towards the normal that means angle of incidence will be greater than angle of reflection.

Question 13.
What is total internal reflection?
Answer:
The phenomenon of reflection of light when a ray of light traveling in a denser medium gets incident at the interface of two media at an angle greater than critical angle is called total internal reflection.

Question 14.
Write the application of total internal reflection.
Answer:
The applications of total internal reflection are.

1. To explain the sparking nature of diamond.
2. To explain the formation of mirages
3. It is used in optic fiber cable
4. It is used in endoscopy.

Question 15.
What do you mean by endoscopy?
Answer:
Endoscopy is an instrument by which doctors can really see the inside of the stomach. This in statement works using the principle of total internal reflection.

Question 16.
Define mirage? How is it formed.
Answer:
Mirage is an optical illusion created by total internal reflection of light Under normal circumstances the density of air is uniform on tar roads and hence light travels in straight line. The air layer in contact with earth gets heated up and becomes rare when compared to the upper strata of atmosphere.

Light coming from the distant objects is total internally reflected. This creates an illusion of reflection in water. The inverted image caused due to the hot air volume below is responsible for this. This phenomenon is rare in case of positions above the level of the observer.

Question 17.
What is a lens? Name the types of lens.
Answer:
Any curved piece of transparent medium is called a lens.
The two types of lens are

1. convex lens
2. concave lens.

Question 18.
What is Spectrum?
Answer:
A band of seven colors (VIBGYOR) formed by splitting of white light is called a spectrum.

Question 19.
Draw a neat diagram to show the refraction of light in a prism.
Answer:

Question 20.
The bottom of a water tank appears to be raised.
Answer:
The bottom of the water tank appears to be raised because the light gets refracted when it enters a different medium.

Question 21.
A pencil partially immersed in an oblique manner in water appears to be bent.
Answer:
A pencil partially immersed in an oblique manner in water appears to be bent due to the refraction of light.

Question 22.
Stars appear to twinkling.
Answer:
Stars appear to be twinkling as the beams of light deviate from their path due to refraction.

Question 23.
In the rainbow, we may not see all the seven colors.
Answer:
In the rainbow, we may not see all the seven colors due to the overlapping of colors.

Question 24.
Diamond sparkles.
Answer:
Diamond sparkles due to the effect of total internal reflection.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 22 Evolution of Life

KSEEB Class 8 Science Chapter 22 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement / question choose the right answer.

Question 1.
The term not dilute soup was used by.
(a) Oparin
(b) Darwin
(c) Haldane
(d) Pasteur
Answer:
(c) Haldane

Question 2.
Which gas was absent in the atmosphere at the time of origin of life.
(a) Ammonia
(b) Hydrogen
(c) Oxygen
(d) Methane
Answer:
(c) Oxygen

Question 3.
The first organisms on primitive earth were
(a) Autotrophic
(b) Heterotrophic and anaerobic
(c) Parasitic
(d) Prokaryotic and autotrophic
Answer:
(b) Heterotrophic and anaerobic

Question 4.
The greatest weakness in Darwin’s theory was his Failure to explain.
(a) Over production
(b) Survival of the fittest
(c) Struggle for existence
(d) Variations
Answer:
(d) Variations

II. Fill in the blanks with suitable words:

Question 1.
Earth was a hot revolving ball of ………… about 4.8 billions of years age.
Answer:
Gas

Question 2.
Lightest element hydrogen was found in the ………… layer of the earliest earth.
Answer:
Outermost

Question 3.
Variations caused by sudden genetic changes are called ………..
Answer:
Mutation

Question 4.
Darwin explained the survival of the fittest but not their ………..
Answer:
Arrival

III. Match the following:

Answer:

1. (d)
2. (c )
3. (b)
4. (e)

IV. Answer the followings:

Question 1.
What is organic evolution
Answer:
The slow gradual process by which living organism have undergone changes from the single celled forms to the many celled forms of life is known as organic evolution.

Question 2.
Explain Lamarck’s theory of use and disuse of organs with suitable example.
Answer:
A Lamarck’s theory is based on three main ides namely new needs, use and disuse of organs and inheritance of acquired characters. The appearance of new needs forces the organism to put in additional efforts to fulfill. It may put a part of a body into more and more frequent use.

Similarly, it may also be necessary for an organism to put a part of its body into less use or may not use at all. This idea is known as use and disuse of organs. Any part of the body that is more and more used is likeiy to grow larger and become better and stronger.

In the same way any part of body which is less frequently used has the tendency to become less prominent and may even ultimately disappear. Thus by a differential over use and disuse of various body parts, an organism would change to some extent and acquire new characters.

For example: for over use: Giraffe’s ancestors were small as deer. Giraffes started stretching their neck and forelimbs in order to reach the leaves of taller plants due to the severe competition from other herbivores and drought. This continued for several generations and as a result neck and forelimbs became longer. Example for disuse: The ancestors of snake had four well developed limbs. Snakes were hunted by more advanced group of animals. In order to survive they started crawling on the ground and spent most of -heir time hiding in crevices and holes. This resulted in the limbs becoming degenerate and ultimately disappear.

Question 3.
What is the role of variations in evolution?
Answer:
Darwin found that generally, the young ones of an organism show differences compared to the parent. He described the differences as variations which are the rule of nature which helps an organism to adjust better to the environment.

Question 4.
What is the mutation?
Answer:
Sudden changes to the genetic makeup of an organism when it is subjected to higher environmental temperature or high energy radiation is called a mutation.

Question 5.
What is neo – Darwinism?
Answer:
Neo Darwinism is the modern theory on organic evolution, the synthesis of ideas from the theory of natural selection, and mutation theory in the light of present knowledge on how mutation occurs.

Question 6.
Which organisms changed the earth’s atmosphere from reducing to oxidizing type?
Answer:
The appearance of autographs in the form of blue-green algae changed the situation on earth. These organisms released free molecular oxygen into the atmosphere, gradually transforming it into an oxidizing type.

Question 7.
What were the limitations found in Darwinism and Lamarck ism?
Answer:

1. Limitation in Darwinism
   • Darwin failed to recognize the source of variations in organisms
   • He had no idea of the mechanism of inheritance.
   • He explained the survival of fittest but not their arrival.
2. Limitation of Lamarck ism
   • His theory cannot explain how body cells pass on the acquired characteristic to reproductive cells.
   • Experiments have shown that acquired characters are not inherited and inherited characters are not acquired.

KSEEB Class 8 Science Chapter 22 Additional Questions & Answers

I. Answer the following :

Question 1.
Who is the scientist conducted a swan-necked flask experiment?
Answer:
The famous swan-necked flask experiment was conducted by Louis Pasteur.

Question 2.
Explain swan-necked flask experiment.
Answer:
The famous swan-necked flask experiment was conducted by Louis Pasteur. and he proved beyond doubt that all forms of life arise only from preexisting life.

Question 3.
Who proposed theory of chemical evolution?
Answer:
Theory of chemical evolution was proposed by oparin and Handane independently.

Question 4.
Write the assumptions of theory of chemical evolution.
Answer:
Assumptions of theory of chemical evolution are:

1. The Earth’s surface and atmosphere during the first billion years of its existence were radically different from those of days conditions.
2. The primitive earth’s atmosphere did not have oxygen.
3. The first life arose from a series of chemical reactions.
4. Solar radiation, ultraviolet rays, and lightning must have been the chief sources of energy for these chemical reactions.

Question 5.
Explain the initial days of Earth’s.
Answer:
In the initial days of earth’s formation, heavy elements such as iron and nickel were present in the center of the earth. Comparatively lighter ones like aluminum and silicon formed the middle layer, elements like hydrogen, oxygen and carbon were found in the outermost layer. Due to the high temperature, the atoms of these elements could not combine to the molecule as the earth started cooling gradually the atoms started combining to form molecules.

Question 6.
Mention the earliest molecules formed which became the basic molecules for the origin of life.
Answer:
The earliest molecules formed were those of H_2, N_2, NH_3, CH_4, CO₂ and water vapor which became the basic molecules for the origin of life.

Question 7.
Name the earliest organic molecules formed.
Answer:
Simple sugars, fatty acids, glycerol, amino acids and nitrogen bases were the earliest organic molecules formed which helped in the origin of life.

Question 8.
Explain Haldane’s view on origin of life.
Answer:
As the earth cooled. The simple organic compound combined among them selves to form complex organic compounds, due to the accumulation of these complex organic molecules, the sea water ultimately became a sort of a ‘hot dilute soup’. In this soup, molecules interacted and aggregated to form more complex molecules called coaCervantes.

Due to their affinity towards water molecules an envelope of water molecules formed which increased the chemical reactions and stalled exhibiting the basic properties of life such as metabolism growth and reproduction. In course of time coacervates became established in to the first living system known as prolobionts.

Which functioned as the first enzymes and leading to the formation of first cells. The first forms of life obtained energy by the fermentation of organic compounds they were thus heterotrophs and anaerobic organisms.

Question 9.
What is organic evolution?
Answer:
The slow gradual process by which living organisms have undergone changes from the single-celled forms to the many-celled forms of life is known as organic evolution.

Question 10.
Mention the principles of Lamarck ism theory.
Answer:
The Lamarck ism theory is based on three principles they are:

1. New needs
2. use and disuse of organs and
3. Inheritance of acquired characters.

Question 11.
Mention the drawbacks of Lamarck’s ideas.
Answer:
Lamarck’s ideas had some-drawbacks.

1. His theory cannot explain how body cells pass on the acquired characteristic to reproductive cells.
2. Experiments have shown that acquired characters are not inherited and inherited characters are not acquired.

Question 12.
Who proposed a theory of Natural Selection.
Answer:
Charles Darwin proposed a theory of Natural selection in 1859. It is more popularly known as ‘Darwinism’.

Question 13.
Mention the principles of Darwinism theory.
Answer:
Darwinism theory is based on the following principles.

1. Overproduction
2. Struggle for existence
3. Variation
4. Natural selection
5. Survival of the fittest.

Question 14.
Explain Darwin’s theory of overproduction.
Answer:
Overproduction: All organisms have a natural capacity to produce a large number of young ones. This capacity is known as overproduction.

Question 15.
Explain Darwin’s theory of the struggle for existence.
Answer:
As a result of high rate of reproduction, there must be competition between individuals. It is for sharing food water, living space and other resources. This competition was described by Darwin as a struggle for existence.

Question 16.
Explain Darwin’s principles of variation.
Answer:
Generally, the young ones show differences compared to the parents. This is variation and they help the organisms to adjust better to the environment.

Question 17.
Explain Darwin’s principles of Natural selection.
Answer:
According to Darwin nature selects only those organisms that have favorable variations.

Question 18.
Explain the survival of the fittest.
Answer:
The naturally selected organisms which have developed advantageous variations have a better chance of survival less adopted or not adopted get eliminated. This idea is known as survival of the fittest.

Question 19.
Mention the drawbacks of Darwin’s theory.
Answer:
Darwin failed to recognize the source of variations in organisms. He had no idea of the mechanism of inheritance. He explained the survival of fittest but not their arrival.

KSEEB Solutions for Class 8 Science

Karnataka Board Class 8 Science Chapter 9 Force and Newton’s Laws of Motion

KSEEB Class 8 Science Chapter 9 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statement/ question. Choose the right answer.

Question 1.
Which one of the following is not correct – Action and reaction
a) act on the same body
b) are equal
c) are opposite
d) act on different bodies
Answer:
d) act on different bodies

Question 2.
If the forces acting on an object are balanced then
a) the object will be accelerated
b) the object will be in motion
c) the object will have zero acceleration,
d) the object loses its shape
Answer:
c) the object will have zero acceleration

Question 3.
The correct way to write S.I. unit of force is
a) Newtons
b) newton
c) newtons
d) newton
Answer:
b) newton

II. Fill in the blanks

Question 1.
Inertia of an object is proportional to its ……………
Answer:
mass

Question 2.
The SI unit of momentum is ………..
Answer:
kg ms^-1

Question 3.
To cause acceleration in an object, the necessary factor is unbalanced ……….
Answer:
force

Question 4.
Newton’s first law of motion is also called law of …………..
Answer:
inertia

Question 5.
The suitcases kept in a moving bus move forward when the brakes are applied suddenly this is due to ……….
Answer:
inertia

III. Answer the following.

Question 1.
In a tug of war game if the two teams exert equal forces none of the team wons. Why?
Answer:
In a tug of war game, if the two team exert equal forces none of the team wons since it maintain the tug in the equilibrium position or in the same state as the forces are balanced forces.

Question 2.
Which of the following has greater momentum?
a) An object of mass 2 kg moving with uniform velocity of 2 ms^-1
b) An object of 1 kg mass moving with uniform velocity of 3 ms^-1
Answer:
a) Mass = 2 kg
Velocity = 2 ms^-1
Momentum M = mass × velocity
= 2 x 2 = 4 kg ms^-1

b) Mass m = 1 kg
Velocity v = 3 ms^-1
Momentum M = mass × velocity
= 1 x 3 = 3 kg ms^-1
Therefore object of mass 2 kg moving with uniform velocity of 2 ms^-1 has greater momentum.

Question 3.
Which of the following has greater inertia?
a) 50 paisa coin
b) one rupee coin
c) five rupee coin
Answer:
c) five rupee coin has greater inertia.

Question 4.
State any two illustrations for Newton’s third law of motion.
Answer:

1. A swimmer pushes the water backward to move forward
2. A boatman Standing in a boat which is in the river pushes the river bank with the help of a long pole. So the boat moves forward, equal to the force applied in the opposite direction.

Question 5.
Distinguish between balanced and unbalanced forces.
Answer:

1. Balanced forces :
   • The effect of the force cannot be observed.
   • No change in the speed or direction of the motion or both.
   • Equilibrium position is maintained,
2. Unbalanced force :
   • The effect of the force can be observed.
   • Change in the speed or direction of the motion or both.
   • Equilibrium position is not maintained.

Question 6.
State newton’s second law of motion in the terms of momentum.
Answer:
The acceleration given to a body by a force applied to it is directly proportional to the force and in the same direction of the force and inversely proportional to the mass of the body. F = ma

IV. Give a reason for the following.

Question 1.
It is dangerous to get down from a moving bus even if the bus is moving slowly.
Answer:
The person getting down from a moving bus runs for a certain distance in the direction of the bus due to inertia which may lead to an accident. Therefore it is dangerous to get down from a moving bus.

Question 2.
An athlete in a long-jump runs a distance before taking the leap.
Answer:
It is possible to jump a longer distance if the athlete runs a distance before taking the leap. This is because the acceleration given to a body by a force applied to it is directly proportional to the force. When a body moves, it wilt continue to move with some velocity when no force acts on it. According to this principle, if an athlete runs from a distance, he/she can jump a longer distance with the same force.

Question 3.
Usually, a fielder in a cricket match takes a catch by moving his hands in the direction of the motion of a cricket ball.
Answer:
Usually, a fielder in a cricket match takes a catch by after taking the moving his hands in the direction of the motion Of cricket ball. Due to inertia, the ball continues in its state of uniform motion in a straight line in the same direction. So the impact on the hands will be less.

V. Solve the problems.

Question 1.
Calculate the force required to change the velocity, of an object of mass 8kg from 4 ms-1 to 6 ms-1 in 2 seconds.
Answer:
Data :
m = 8 kg
u = 4 ms^-1
v = 6 ms^-1
t = 2 sec
a = ?
F = ?
Solution:
a = \(\frac { v-u }{ t }\)
= \(\frac { 6-4 }{ 2 }\)
= \(\frac { 2 }{ 2 }\) = 1 ms^-1
F = ma
=8 × 1 = 8 kg ms^-2 = 8 N

Question 2.
A force of 25 newtons is applied on an object of mass 10 kg moving with a velocity of 5 ms^-1 If the object gains a velocity of 10
ms^-1. Calculate the time interval.
Answer:
Data :
F = 25 N
m = 10 kg
u = 5 ms^-1
v = 10 ms^-1
a = ?
t = ?
Solution :
F = ma
ma = F
10 a = 25
a = \(\frac { 25 }{ 10 }\) = 2.5 ms^-2
v = u + at
10 = 5 + 2.5 t
2.5 t = 10 – 5
2.5 t = 5
t = \(\frac {5 }{ 2.5 }\) = 2 sec

KSEEB Class 8 Science Chapter 9 Additional Questions & Answers

Question 1.
Define force? Mention the effect of force.
Answer:
Force is a physical quantity that changes the state of the rest of a body or that changes the velocity of a body. Effects of force applied on an object can

1. Change the velocity of an object
2. Change the shape of an object.

Question 2.
What are unbalanced forces?
Answer:
The effect of force will be observed when an unbalanced force acts on an object. Unbalanced forced acting on an object, changes its speed or direction of motion.

Question 3.
What are balanced forces?
Answer:
If two or more forces acting on the same object keep the object in equilibrium position or in the same state, then the forces are balanced forces.

Question 4.
What is meant by Frictional force?
Answer:
Friction is the opposing force which comes, whenever there is relative motion between two bodies.

Question 5.
What is meant by inertia?
Answer:
The tendency of the objects to remain at rest or state of motion when no forces act on them is called inertia.

Question 6.
State Newton’s first law of motion.
Answer:
Everybody continues in its state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it.

Question 7.
What are the SI units of mass and acceleration?
Answer:
SI unit of mass is kg SI unit of acceleration is ms-2

Question 8.
Calculate the force required to change the velocity of an object of mass 4 kg from 2 ms^-2 to 4 ms^-2 in one second.
Answer:
Solution
F = ma
m = 4 kg
a = 2 ms^-2
F = ?
F = 4 kg x acceleration
F = 4 x 2
= 8 kg ms^-1 or 8 newton or 8 N.

Question 9.
An object of mass 10 kg is moving with an initial velocity of 2 ms^-1. To make it come to rest in one second, what should be the unbalanced force?
Answer:
Solution,
initial velocity = 2 ms^-1
velocity at rest = 0 ms^-1
time interval = 1 second
mass m = 10 kg
change in velocity in one second or acceleration
= \(\frac { 0-2 }{ 1 }\) = 2 ms^-1
F = ma
F = 10 × 2
= 20 kg ms^-2 or -20 newton or-20 N.
The negative sign tells us that the force exerted is opposite to the direction of motion.

Question 10.
An object of mass 20 kg is moving with an initial velocity of 2 ms^-1. If its velocity changes to 4 ms^-1 in one second. What should be the force acting on it? What will be the direction of the motion?
Answer:
Solution
F = ma
m = 20 kg
a = \(\frac { 4-2 }{ 1 }\) = 2 ms^-1
F = 20 x 2 = 40 newton or 40 N.
The object continues to move in the same direction as the force applied is in the same direction.

Question 11.
State the conservation of momentum
Answer:
Conservation of momentum states that the total momentum of a system conserved when the net external force acting on the system is zero.
mv + MV = 0 or mv = – MV

Question 12.
State Newton’s third law of motion.
Answer:
“To every action there is always an opposed and equal reaction or The mutual actions of two bodies upon each other are always equal and directed in opposite direction.

Question 13.
A bullet of mass 25 g is fired from a rifle of mass 2 kg. Imagine that no other forces are acting on the system. If the bullet travels with a velocity of 2 ms^-1, what will be the velocity of the recoil of the rifle?
Answer:
Momentum of the rifle = momentum of the bullet
Mass of the rifle × velocity of recoil = mass of the bullet × Velocity of the bullet
2 × velocity of recoil = \(\frac { 25 }{ 1000 }\) × 2
2 × velocity of recoil = \(\frac { 1\times 2 }{ 40 }\) = \(\frac { 1 }{ 2 }\)
velocity of recoil = \(\frac { 1 }{ 2 }\) ×  \(\frac { 1 }{ 20 }\) =  \(\frac { 1 }{ 40 }\) =0.0025 ms^-1

KSEEB Solutions for Class 8 Science