PSEB 8TH CLASS SCIENCE SIMPLIFIED MATERIAL MISSION 100% FULLY SOLVED

• These questions have been framed keeping in mind the students who score
  less than 40% marks in science subject or may fail in science .
  → students who have prepared these questions satisfactorily, there is no
  chance of failure.
• All the important questions in these questions have been prepared keeping
  in mind the old paper of P.S.E.B. and Model Test Paper 2023.
  Note:- This questionnaire has been prepared only for the weak students in
  science subject. By using this booklet you can pass but the entire syllabus
  should be read to get full marks.

Multiple Choice Questions (MCQs) for Class 8 Science

Here are 56 important multiple-choice questions from the Class 8 Science question bank to help students prepare for their exams. These questions cover various topics from the syllabus and are designed to strengthen fundamental concepts.

1 Mark Questions

1. Broadcasting is one method of:

• (a) Weeding
• (b) Sowing
• (c) Irrigation
• (d) Harvesting
  Answer: (b) Sowing

1. The type of irrigation best suited for places with water scarcity is:

• (a) Furrow irrigation
• (b) Sprinkle irrigation
• (c) Drip irrigation
• (d) Basin irrigation
  Answer: (c) Drip irrigation

1. Earthworms are used for the preparation of:

• (a) Compost
• (b) Manure
• (c) Green manure
• (d) Vermicompost
  Answer: (d) Vermicompost

1. The process of growing crops without chemical fertilizers is called:

• (a) Organic farming
• (b) Hybridization
• (c) Mixed cropping
• (d) Crop rotation
  Answer: (a) Organic farming

1. The three macronutrients are:

• (a) Phosphorus, Carbon, and Iron
• (b) Nitrogen, Phosphorus, and Potassium
• (c) Potassium, Calcium, and Magnesium
• (d) Nitrogen, Hydrogen, and Chlorine
  Answer: (b) Nitrogen, Phosphorus, and Potassium

1. The process of cleaning grains from chaff is called:

• (a) Harvesting
• (b) Broadcasting
• (c) Threshing
• (d) Winnowing
  Answer: (c) Threshing

1. Which of the following is not caused by a bacterial disease?

• (a) Typhoid
• (b) Tetanus
• (c) Cholera
• (d) Malaria
  Answer: (d) Malaria

1. Which one of the following cannot definitely be called living or non-living?

• (a) Virus
• (b) Algae
• (c) Bacteria
• (d) Fungi
  Answer: (a) Virus

1. Which of these can make its own food?

• (a) Algae
• (b) Bread mould
• (c) Diatoms
• (d) Amoeba
  Answer: (a) Algae

1. Which of these diseases is prevented by vaccination?
   • (a) Malaria
   • (b) Polio
   • (c) Ringworm
   • (d) Cholera
     Answer: (b) Polio
2. High-quality coal is:
   • (a) Peat
   • (b) Lignite
   • (c) Bituminous
   • (d) Anthracite
     Answer: (d) Anthracite
3. An inexhaustible source of energy is:
   • (a) Coal
   • (b) Petroleum
   • (c) Air
   • (d) Natural gas
     Answer: (c) Air
4. There are no coal mines in this state:
   • (a) Odisha
   • (b) Punjab
   • (c) Jharkhand
   • (d) West Bengal
     Answer: (b) Punjab
5. Coal product used to repel moths is:
   • (a) Coal tar
   • (b) Coke
   • (c) Naphthalene
   • (d) Benzene
     Answer: (c) Naphthalene
6. Which of the following gases is used in combustion?
   • (a) Hydrogen
   • (b) Oxygen
   • (c) Nitrogen
   • (d) Carbon dioxide
     Answer: (b) Oxygen
7. The burning of CNG (compressed natural gas) is an example of:
   • (a) Rapid combustion
   • (b) Spontaneous combustion
   • (c) Slow combustion
   • (d) None of the above
     Answer: (a) Rapid combustion
8. Which of the following is an example of spontaneous combustion?
   • (a) Burning of petrol
   • (b) Burning of magnesium ribbon
   • (c) Burning of camphor
   • (d) Burning of white phosphorus
     Answer: (d) Burning of white phosphorus
9. Minimum temperature at which fuel ignites:
   • (a) Melting temperature
   • (b) Boiling temperature
   • (c) Ignition temperature
   • (d) None of these
     Answer: (c) Ignition temperature
10. Biodiversity Day is celebrated on:
    • (a) 22nd February
    • (b) 22nd March
    • (c) 22nd April
    • (d) 22nd May
      Answer: (d) 22nd May
11. 100% of this species of animals is found in India:
    • (a) Elephants
    • (b) Tigers
    • (c) Asian Lions
    • (d) Wild buffaloes
      Answer: (c) Asian Lions
12. Flying squirrel is an endemic species of:
    • (a) Gir Forest, Gujarat
    • (b) Panchmari Biosphere Reserve
    • (c) Kaziranga National Park
    • (d) Jim Corbett National Park
      Answer: (b) Panchmari Biosphere Reserve
13. This species has become extinct from India:
    • (a) Cheetah
    • (b) Bengal tiger
    • (c) Wild dog
    • (d) Wild Ass
      Answer: (a) Cheetah
14. This species is endemic to Gujarat:
    • (a) Wild Ass
    • (b) Bengal tiger
    • (c) Rhinoceros
    • (d) Elephant
      Answer: (a) Wild Ass
15. Which of these are the male reproductive organs of humans?
    • (a) Sperm
    • (b) Ova
    • (c) Testes
    • (d) Ovaries
      Answer: (c) Testes
16. Which of the following is a hermaphrodite animal?
    • (a) Frog
    • (b) Cow
    • (c) Dog
    • (d) Earthworm
      Answer: (d) Earthworm
17. Where does fertilization take place in humans?
    • (a) Oviduct
    • (b) Uterus
    • (c) Ovary
    • (d) Vagina
      Answer: (a) Oviduct
18. In a mosquito, the eggs hatch to produce:
    • (a) Pupa
    • (b) Embryo
    • (c) Larva
    • (d) Adult mosquito
      Answer: (c) Larva
19. The fusion of sperm and egg produces:
    • (a) Zygote
    • (b) Gamete
    • (c) Embryo
    • (d) Oviduct
      Answer: (a) Zygote
20. Reproductive age in women starts when their:
    • (a) Menstruation starts
    • (b) Height increases
    • (c) Weight increases
    • (d) Menopause starts
      Answer: (a) Menstruation starts
21. The right meal for adolescents is:
    • (a) Noodles, coke, and chips
    • (b) Pizza, chips, and coke
    • (c) Pizza, noodles, and burgers
    • (d) Chapati, pulses, and vegetables
      Answer: (d) Chapati, pulses, and vegetables
22. Testes in males produce:
    • (a) Estrogen
    • (b) Testosterone
    • (c) Insulin
    • (d) Progesterone
      Answer: (b) Testosterone
23. Deficiency of iodine in the diet causes:
    • (a) Goitre
    • (b) Diabetes
    • (c) Menopause
    • (d) Menstruation
      Answer: (a) Goitre
24. The hormone whose deficiency may cause diabetes is:
    • (a) Estrogen
    • (b) Testosterone
    • (c) Insulin
    • (d) Thyroxine
      Answer: (c) Insulin
25. Which type of friction is greatest?
    • (a) Sliding friction
    • (b) Rolling friction
    • (c) Static friction
    • (d) None of these
      Answer: (c) Static friction
26. We use these measures to minimize friction:
    • (a) Make surfaces smooth
    • (b) Use ball bearings
    • (c) Apply oil or grease
    • (d) All of the above
      Answer: (d) All of the above
27. We adopt the following measures to increase friction:
    • (a) Use rollers
    • (b) Treads on tyres
    • (c) Use oil or grease
    • (d) Make surfaces smooth
      Answer: (b) Treads on tyres
28. Which of the following is an example of sliding friction?
    • (a) Dragging a sandbag on the floor
    • (b) Use of rollers in a trolley
    • (c) Use of ball bearings
    • (d) Laborers use rollers to pull logs of wood
      Answer: (a) Dragging a sandbag on the floor
29. This shape helps aquatic animals to swim in water:
    • (a) Flat body
    • (b) Streamlined body
    • (c) Broad body
    • (d) Rough body
      Answer: (b) Streamlined body
30. The amplitude of the sound decides its:
    • (a) Speed
    • (b) Loudness
    • (c) Pitch
    • (d) Source
      Answer: (b) Loudness
31. Sound can travel in:
    • (a) Gases only
    • (b) Liquids only
    • (c) Solids only
    • (d) Solids, liquids, and gases
      Answer: (d) Solids, liquids, and gases
32. When you hold a ringing bell with your hand:
    • (a) The bell stops vibrating and stops ringing
    • (b) The bell starts vibrating with inaudible frequency
    • (c) No change in vibration
    • (d) Amplitude increases
      Answer: (a) The bell stops vibrating and stops ringing
33. This is a good conductor of electricity:
    • (a) Bakelite
    • (b) Rubber
    • (c) PVC
    • (d) Graphite
      Answer: (d) Graphite
34. The coating of this metal on iron is called galvanization:
    • (a) Gold
    • (b) Silver
    • (c) Zinc
    • (d) Mercury
      Answer: (c) Zinc
35. Which liquid is not a good conductor of electricity?
    • (a) Lemon juice
    • (b) Distilled water
    • (c) Common salt solution
    • (d) Copper sulphate solution
      Answer: (b) Distilled water
36. It is based on the chemical effect of electricity:
    • (a) Electroplating
    • (b) Glowing of bulb
    • (c) Sublimation
    • (d) Distillation
      Answer: (a) Electroplating
37. Rims of vehicles are usually coated with:
    • (a) Gold
    • (b) Silver
    • (c) Chromium
    • (d) Copper
      Answer: (c) Chromium
38. Which of these are epidemic?
    • (a) Dengue
    • (b) Swine flu
    • (c) Cholera
    • (d) All of the above
      Answer: (d) All of the above
39. It is not an epidemic, but a pandemic:
    • (a) Dengue in Delhi
    • (b) Covid-19
    • (c) Plague of Bengal
    • (d) Drought in Ethiopia
      Answer: (b) Covid-19
40. The frequency of an earthquake is measured by:
    • (a) Barometer
    • (b) Anemometer
    • (c) Seismograph
    • (d) Letometer
      Answer: (c) Seismograph
41. Charge is produced by the transfer of:
    • (a) Electrons
    • (b) Protons
    • (c) Atoms
    • (d) Neutrons
      Answer: (a) Electrons
42. During lightning and thunder, we should take shelter:
    • (a) Under a tall tree
    • (b) Near an electric tower
    • (c) Inside a building
    • (d) Under an umbrella
      Answer: (c) Inside a building
43. Carry the sensation of sight to the brain:
    • (a) Rainbow
    • (b) Yellow spot
    • (c) Blind spot
    • (d) Optic nerve
      Answer: (d) Optic nerve
44. The least distance of distinct vision of a normal human eye is at:
    • (a) Infinity
    • (b) 50 m
    • (c) 25 cm
    • (d) 5 cm
      Answer: (c) 25 cm
45. Eye fluid present behind the lens in the eyeball:
    • (a) Aqueous humor
    • (b) Vitreous humor
    • (c) Tears
    • (d) Saliva
      Answer: (b) Vitreous humor
46. It can rotate one eye towards the backside and the other towards the front side:
    • (a) Butterfly
    • (b) Chameleon
    • (c) Housefly
    • (d) Owl
      Answer: (b) Chameleon
47. It is used to see different beautiful patterns:
    • (a) Solar filter
    • (b) Mirror
    • (c) Telescope
    • (d) Kaleidoscope
      Answer: (d) Kaleidoscope

These MCQs are designed to help Class 8 students revise key concepts and prepare effectively for their exams. For more study materials and solutions, visit Best Solution Class.

Prepared by: Neeraj Singh Kanwar (Science Master), GHS Bhagowal, Hoshiarpur.

Fill in the Blanks Questions for Class 8 Science

Here are 68 important fill-in-the-blank questions from the Class 8 Science question bank to help students prepare for their exams. These questions cover key concepts across various chapters of the syllabus.

1 Mark Questions

1. Any microorganism or animal that attacks crops is called a pest.
2. Only one type of plant grown in a field is called a crop.
3. Crops grown in winter are called Rabi crops.
4. Production and management of fish is called pisciculture.
5. Selling of crop yield in the market is called marketing.
6. Grains are also stored at home in iron sheet silos.
7. Microorganisms can be seen with the help of a microscope.
8. Lactobacillus is the organism that helps in the formation of curd.
9. Fungi like Aspergillus cause food poisoning.
10. During pasteurization, milk is heated from 70°C to 100°C and then suddenly chilled and stored.
11. Coal and petroleum are natural fossil fuels.
12. Air and sunlight, which cannot be totally consumed by human beings, are called inexhaustible natural resources.
13. Conversion of buried dead vegetation into coal is called carbonization.
14. Burning of coal in air or oxygen produces carbon dioxide gas.
15. The calorific value of LPG is 55000 KJ/Kg.
16. The outermost part of the flame is the hottest.
17. Oxygen gas or air is necessary for combustion.
18. Burning of wood and coal causes pollution of air.
19. A liquid fuel used in homes is LPG.
20. Fuel must be heated to its ignition temperature before it starts burning.
21. Fire produced by oil cannot be controlled by water.
22. Migratory birds come to India in winter season.
23. Endemic species are found only in a particular area.
24. Black buck, the state mammal of Punjab, is also an endangered animal.
25. The first week of October is celebrated as Wildlife Protection Week.
26. Kanjli wetland is situated in Kapurthala district of Punjab.
27. The process of converting fertile land into drought is called desertification.
28. The process of fusion of sperm and ovum is known as fertilization.
29. Union of gametes does not take place during asexual reproduction.
30. Binary fission occurs in Amoeba.
31. In humans, fertilization is internal.
32. The zygote, after repeated division, gives rise to an embryo.
33. If the ovum is fertilized by a sperm, a zygote is formed.
34. Endocrine glands release hormones directly into the blood.
35. The sex chromosome of the father determines the sex of the unborn baby.
36. The chemical substances secreted by glands are called hormones.
37. Acne and pimples are common during puberty due to the increased activity of oil and sweat glands.
38. Pressure is force per unit area.
39. Gravitational force is a non-contact force.
40. The south pole of a magnet attracts the north pole of another magnet.
41. To draw water from the well, we have to pull at the rope.
42. A charged object attracts an uncharged object towards it.
43. Frictional force is an opposing force that comes into play when one surface moves over another surface.
44. Friction on bodies moving through fluids is called fluid friction.
45. Rubbing both hands produces heat due to friction.
46. The time taken by an object to complete one vibration is called time period.
47. Sound requires a medium to travel.
48. Sound travels fastest in solids.
49. Hertz (Hz) is a unit of frequency.
50. Unwanted sound is called noise.
51. A sound with a frequency greater than 20,000 Hz is called ultrasound.
52. Shrillness of the sound is called pitch.
53. Metals are good conductors of electricity.
54. A magnetic tester uses the magnetic effect of electric current.
55. An electrical tester uses the electric effect of electrical current.
56. An electrolyte dissociates into ions when direct current passes through it.
57. Copper and brass utensils are coated with tin metal.
58. Covid-19 is an epidemic disease.
59. On rubbing two bodies, we get positive and negative charges.
60. An epidemic is the rapid spread of a disease in a large population in a particular area.
61. Air in motion is called wind.
62. An uncharged object can be charged by rubbing.
63. Absence of light is called darkness.
64. Light can pass through transparent bodies/mediums.
65. Sunlight is made up of seven colors.
66. In the human eye, the image is formed at the retina.
67. Chameleon can rotate its eyes in various directions.
68. Production and management of honey is called apiculture.

These fill-in-the-blank questions are designed to help Class 8 students revise important concepts and prepare effectively for their exams. For more study materials and solutions, visit Best Solution Class.

Prepared by: Neeraj Singh Kanwar (Science Master), GHS Bhagowal, Hoshiarpur.

True or False Questions for Class 8 Science

Here are 63 important True/False questions from the Class 8 Science question bank to help students prepare for their exams. These questions cover key concepts across various chapters of the syllabus.

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Mark (✓) for True and (✗) for False

1. Pisciculture deals with growing of fruits and vegetables.

• Answer: ✗ (False)

1. Excessive use of fertilizers can turn soil acidic or basic.

• Answer: ✓ (True)

1. Manure contains more nutrients than chemical fertilizers.

• Answer: ✗ (False)

1. A wooden plank is used for digging the soil.

• Answer: ✗ (False)

1. A plough is an agricultural tool used for tilling the soil.

• Answer: ✓ (True)

1. All living things can be seen with the naked eye.

• Answer: ✗ (False)

1. Anton van Leeuwenhoek was the first person to observe and describe single-celled organisms.

• Answer: ✓ (True)

1. Penicillin is prepared from Penicillium notatum.

• Answer: ✓ (True)

1. Microorganisms that are beneficial to plants and animals are called pathogens.

• Answer: ✗ (False)

1. Fossil fuels can be made in the laboratory.
   • Answer: ✗ (False)
2. CNG is more polluting than diesel.
   • Answer: ✗ (False)
3. Coke is almost the purest form of carbon.
   • Answer: ✓ (True)
4. Coal and petroleum are inexhaustible natural resources of energy.
   • Answer: ✗ (False)
5. Coal-tar is a mixture of various substances.
   • Answer: ✓ (True)
6. The burning of camphor is a rapid combustion.
   • Answer: ✗ (False)
7. Combustion is a physical change.
   • Answer: ✗ (False)
8. Air is essential for combustion.
   • Answer: ✓ (True)
9. Fire caused due to oil can be extinguished by water.
   • Answer: ✗ (False)
10. Cutting of trees is a natural cause of deforestation.
    • Answer: ✗ (False)
11. Wetlands of international level are called Ramsar wetlands.
    • Answer: ✓ (True)
12. Rehmapur Takhni wildlife sanctuary is situated in Hoshiarpur district in Punjab.
    • Answer: ✓ (True)
13. Panda is the endemic animal of Rajasthan.
    • Answer: ✗ (False)
14. Camel is the state animal of Punjab.
    • Answer: ✗ (False)
15. The fauna of a place includes herbs, shrubs, and trees.
    • Answer: ✗ (False)
16. The animals which lay eggs are called oviparous.
    • Answer: ✓ (True)
17. Each sperm is a single cell.
    • Answer: ✓ (True)
18. Hydra reproduces by binary fission.
    • Answer: ✗ (False)
19. A zygote is formed as a result of fertilization.
    • Answer: ✓ (True)
20. In humans, external fertilization takes place.
    • Answer: ✗ (False)
21. Balanced diet is not essential for adolescents.
    • Answer: ✗ (False)
22. The stoppage of menstruation is termed as menarche.
    • Answer: ✗ (False)
23. Ovaries produce testosterone hormone.
    • Answer: ✗ (False)
24. The change from larva to an adult frog is known as metamorphosis.
    • Answer: ✓ (True)
25. Hormones have no role in the growth and development of the body.
    • Answer: ✗ (False)
26. Liquid pressure is least at the bottom of the container.
    • Answer: ✗ (False)
27. Force of friction is a non-contact force.
    • Answer: ✗ (False)
28. North pole of the magnet repels the South pole of another magnet.
    • Answer: ✗ (False)
29. Gravitational force is a contact force.
    • Answer: ✗ (False)
30. A force can change the state of motion of an object.
    • Answer: ✓ (True)
31. Use of rollers in trolley bags makes it difficult to pull the trolley.
    • Answer: ✗ (False)
32. Oiling and greasing minimize the friction.
    • Answer: ✓ (True)
33. We throw sand on a slippery path to increase friction.
    • Answer: ✓ (True)
34. Sound having frequency less than 20 Hertz is known as infrasonic.
    • Answer: ✓ (True)
35. Sound can travel in a vacuum.
    • Answer: ✗ (False)
36. Sound having frequency more than 80dB is harmful.
    • Answer: ✓ (True)
37. Sound of a lion has more frequency than the sound of a mosquito.
    • Answer: ✗ (False)
38. The pitch of a sound depends on the amplitude of its vibrations.
    • Answer: ✗ (False)
39. Sound cannot travel through a string.
    • Answer: ✗ (False)
40. Electric current does not pass through liquids.
    • Answer: ✗ (False)
41. Electroplating uses the heating effects of current.
    • Answer: ✗ (False)
42. An electric tester is used to check if a wire or appliance carries current.
    • Answer: ✓ (True)
43. Artificial jewellery is costlier than gold jewellery.
    • Answer: ✗ (False)
44. Coating of chromium over iron is called galvanization.
    • Answer: ✗ (False)
45. Cyclones, hurricanes, and typhoons are all tropical storms.
    • Answer: ✓ (True)
46. During lightning and thunder, we should stand under a tall tree or an electric pole.
    • Answer: ✗ (False)
47. Lightning conductor is used to save tall buildings and towers from lightning.
    • Answer: ✓ (True)
48. The speed of wind is measured by a seismograph.
    • Answer: ✗ (False)
49. Do not use an umbrella during lightning.
    • Answer: ✓ (True)
50. A candle is a natural source of light.
    • Answer: ✗ (False)
51. The retina is the outermost layer of the eyeball.
    • Answer: ✗ (False)
52. The central hole of the iris is called the pupil.
    • Answer: ✓ (True)
53. Creatures of darkness can only see in bright light.
    • Answer: ✗ (False)
54. The Braille system of writing for blinds was invented by Helen Keller.
    • Answer: ✗ (False)

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These True/False questions are designed to help Class 8 students revise key concepts and prepare effectively for their exams. For more study materials and solutions, visit Best Solution Class.

Match the Column Questions for Class 8 Science

Here are important match-the-column questions from the Class 8 Science question bank to help students prepare for their exams. These questions cover key concepts across various chapters of the syllabus.

Match Column A with Column B

Set 1: Agriculture Tools and Crops

Column A	Column B

1. It is an agriculture tool/machinery which can reap and thresh grains | a. Urea
2. Keeping birds for meat and eggs is called | b. Rabi crops
3. It is a nitrogen rich fertilizer | c. Sharif crops
4. Barley and Mustard | d. Poultry
5. Maize and paddy | e. Combine

Answers:

1. e (Combine)
2. d (Poultry)
3. a (Urea)
4. b (Rabi crops)
5. c (Sharif crops)

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Set 2: Microorganisms

Column A	Column B

1. Streptococcus | a. Algae
2. Penicillium | b. Virus
3. Chlamydomonas | c. Bacteria
4. HIV | d. Fungi

Answers:

1. c (Bacteria)
2. d (Fungi)
3. a (Algae)
4. b (Virus)

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Set 3: Wildlife and Conservation

Column A	Column B

1. State mammal of Punjab | a. Red Data Book
2. Goat like wild deer found in Kandi area of Punjab and lower Himachal | b. Biodiversity
3. A book having record of endangered species of organisms | c. Extinct
4. Presence of so many species of plants, animals and microorganisms | d. Barking deer
5. Species which have totally vanished | e. Black buck

Answers:

1. e (Black buck)
2. d (Barking deer)
3. a (Red Data Book)
4. b (Biodiversity)
5. c (Extinct)

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Set 4: Reproduction

Column A	Column B

1. The process of producing young ones of own kind | a. Oviparous
2. A method of asexual reproduction in hydra | b. Zygote
3. Its fertilization takes place inside water | c. Reproduction
4. Egg laying animals | d. Frog
5. Sperm and egg/ovum fuse to form | e. Budding

Answers:

1. c (Reproduction)
2. e (Budding)
3. d (Frog)
4. a (Oviparous)
5. b (Zygote)

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Set 5: Endocrine Glands and Hormones

Column A	Column B

1. Pancreas | a. Goitre
2. Thyroid gland | b. Insulin
3. Testes | c. Estrogen
4. Pituitary gland | d. Testosterone
5. Ovary | e. Growth hormone

Answers:

1. b (Insulin)
2. a (Goitre)
3. d (Testosterone)
4. e (Growth hormone)
5. c (Estrogen)

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Set 6: Forces and Pressure

Column A	Column B

1. Press | a. Pull or push
2. Gravitational force | b. Working of a dropper
3. Atmospheric pressure | c. Force/area
4. Force | d. Opposes the motion of the body
5. Friction force | e. Non-contact force

Answers:

1. c (Force/area)
2. e (Non-contact force)
3. b (Working of a dropper)
4. a (Pull or push)
5. d (Opposes the motion of the body)

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Set 7: Friction and Motion

Column A	Column B

1. Ships, boats and airplanes are made in this shape | a. Ball bearing
2. The sole of shoes of the athletes have special feature called | b. Atmospheric friction
3. The opposing force due to fluid friction | c. Grooves
4. This phenomenon saves us from meteors or shooting stars | d. Streamlined
5. Machinery parts having least friction due to | e. Drag

Answers:

1. d (Streamlined)
2. c (Grooves)
3. e (Drag)
4. b (Atmospheric friction)
5. a (Ball bearing)

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Set 8: Sound

Column A	Column B

1. Noise | a. The unit of frequency
2. Larynx | b. The human organ that produces sound
3. Hertz | c. Loudness
4. Decibel | d. Musical instrument
5. Flute | e. Unwanted sounds

Answers:

1. e (Unwanted sounds)
2. b (The human organ that produces sound)
3. a (The unit of frequency)
4. c (Loudness)
5. d (Musical instrument)

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Set 9: Electricity

Column A	Column B

1. Flow of charge | a. Chromium
2. Source of electric current | b. Electroplating
3. Cycle handles are coated by this metal | c. Galvanization
4. Coating of superior metal over inferior metal using electric current | d. Current
5. Zinc coating on iron plates | e. Electric cell

Answers:

1. d (Current)
2. e (Electric cell)
3. a (Chromium)
4. b (Electroplating)
5. c (Galvanization)

---

Set 10: Natural Phenomena

Column A	Column B

1. In 2020 the pandemic that hit the whole world | a. Gold leaf electroscope
2. Cyclone that hit Orissa in May 2020 | b. Lightning
3. When two charged clouds approach each other it causes | c. Hypocenter
4. It is used to detect the charge on body | d. Covid-19
5. Point inside the earth where earthquake originates | e. Amphan

Answers:

1. d (Covid-19)
2. e (Amphan)
3. b (Lightning)
4. a (Gold leaf electroscope)
5. c (Hypocenter)

---

Set 11: Light and Vision

Column A	Column B

1. During reflection through mirrors the angle of reflection is equal to | a. Cornea
2. This part of eye gives colour to eyes | b. Sun
3. It is a natural source of light | c. Owl
4. It is the front transparent part of sclerotic or sclera | d. Angle of incidence
5. It is a nocturnal animal | e. Iris

Answers:

1. d (Angle of incidence)
2. e (Iris)
3. b (Sun)
4. a (Cornea)
5. c (Owl)

---

Set 12: Combustion and Fuels

Column A	Column B

1. LPG | a. KJ/Kg
2. Calorific value | b. Rapid combustion
3. Fire extinguisher | c. Non combustible
4. Glass | d. CO₂

Answers:

1. b (Rapid combustion)
2. a (KJ/Kg)
3. d (CO₂)
4. c (Non combustible)

---

Set 13: Fuels and Gases

Column A	Column B

1. Used as fuel in kitchens | a. CNG
2. Least polluting fuel for vehicles | b. Coal gas
3. This gas is produced during heating of coal | c. L.P.G

Answers:

1. c (L.P.G)
2. a (CNG)
3. b (Coal gas)

---

These match-the-column questions are designed to help Class 8 students revise key concepts and prepare effectively for their exams. For more study materials and solutions, visit Best Solution Class.

Prepared by: Neeraj Singh Kanwar (Science Master), GHS Bhagowal, Hoshiarpur.

2 MARKS IMPORTANT QUESTION ANSWRS

Question 1

Name two animals reared for milk.

• Cow
• Goat

Question 2

Write down any two ancient methods of irrigation.

• Qanat system
• Canal irrigation

Question 3

What is a plough?
A plough is an agricultural tool used to break and turn the soil to prepare it for the planting of seeds, facilitating aeration and nutrient incorporation.

Question 4

Where are fruits and vegetables stored?
Fruits and vegetables are typically stored in cool, dry places or in refrigerators to prolong freshness and prevent spoilage.

Question 5

Name the major groups of microorganisms.

• Bacteria
• Fungi
• Viruses
• Protozoa
• Algae

Question 6

What is food poisoning?
Food poisoning is a gastrointestinal illness caused by consuming contaminated food or beverages, often resulting from bacteria, viruses, or toxins.

Question 7

Name three diseases caused by fungi in plants.

• Powdery mildew
• Root rot
• Rust disease

Question 8

Name two diseases caused by bacteria in cattle.

• Bovine tuberculosis
• Brucellosis

Question 9

Name any two inexhaustible sources of energy.

• Solar energy
• Wind energy

Question 10

What are Petrochemicals?
Petrochemicals are chemical products derived from petroleum or natural gas, used as feedstock for manufacturing various chemicals, plastics, and fuels.

Question 11

Write the full name of CNG and LPG.

• CNG: Compressed Natural Gas
• LPG: Liquefied Petroleum Gas

Question 12

Which variety of coal is found in most of the coal mines in India?

• Anthracite coal and Bituminous coal are found in most coal mines in India, with Bituminous being the most prevalent.

Question 13

Where is natural gas found in India?

• Natural gas in India is primarily found in regions such as Assam, Gujarat, and in the Krishna-Godavari Basin along the east coast.

Question 14

List the conditions under which combustion can take place.

1. Presence of a combustible material (fuel)
2. Presence of an oxidizer (usually oxygen)
3. Ignition (sufficient heat)

Question 15

Define Ignition temperature.
Ignition temperature is the minimum temperature at which a material (fuel) must be heated for combustion to occur and sustain the fire.

Question 16

Name any two natural causes of deforestation.

1. Forest fires
2. Natural calamities (such as floods and landslides)

Question 17

Which plant is considered best for checking soil erosion?

• The vetiver grass (Chrysopogon zizanioides) is often considered one of the best plants for checking soil erosion.

Question 18

In which districts of Punjab are the following wildlife sanctuaries located?
a) Sito Gunno Wildlife Sanctuary – Located in the Fatehgarh Sahib district.
b) Kathlour Wildlife Sanctuary – Located in the Patiala district.

Question 19

Name any two endangered species found in India.

1. Bengal Tiger
2. Indian Rhino

Question 20

Define the following:
1) Fertilization: The process where a sperm cell combines with an egg cell to form a zygote, leading to the development of a new organism.
2) Metamorphosis: A biological process by which an organism undergoes a significant change in form and physiological state from an immature stage to an adult stage (e.g., a caterpillar transforming into a butterfly).
3) Hermaphrodite animals: Animals that possess both male and female reproductive organs, allowing them to produce both sperm and eggs (e.g., earthworms).
4) Reproduction: The biological process by which new individual organisms are produced from their parents, ensuring the continuation of a species.

:

Question 21

What is male gamete in human called?

• The male gamete in humans is called sperm.

Question 22

Name the different stages in the life cycle of a butterfly.

1. Egg
2. Larva (Caterpillar)
3. Pupa (Chrysalis)
4. Adult Butterfly

Question 23

What is a Zygote?

• A zygote is the fertilized egg that forms when a sperm cell combines with an egg cell, marking the beginning of the development of a new organism.

Question 24

Define adolescence.

• Adolescence is the transitional developmental stage between childhood and adulthood, typically occurring from ages 10 to 19, characterized by physical, emotional, and psychological changes.

Question 25

What will happen if tadpoles are in iodine deficient pond water?

• Tadpoles may develop thyroid-related issues, leading to growth problems and developmental abnormalities, as iodine is essential for their growth and metabolic processes.

Question 26

Why are endocrine glands known as ductless glands?

• Endocrine glands are known as ductless glands because they release hormones directly into the bloodstream rather than through ducts, allowing hormones to be distributed throughout the body.

Question 27

What is force?

• Force is a push or pull acting upon an object, which can cause the object to change its velocity (accelerate), direction, or shape. It is measured in newtons (N).

Question 28

What are contact forces?

• Contact forces are forces that occur when two objects physically touch each other, such as friction, tension, and normal force.

Question 29

What are non-contact forces?

• Non-contact forces are forces that act on an object without physical contact, such as gravitational force, electromagnetic force, and nuclear force.

Question 30

How did early man learn to make fire?

• Early man is believed to have learned to make fire through natural occurrences, such as lightning strikes, and by observing its effects. This knowledge prompted them to create fire using methods like striking flint stones, rubbing sticks together, or using friction techniques to produce heat and ignite tinder.

Question 31

What is drag?

• Drag is a type of frictional force experienced by an object moving through a fluid (such as air or water). It opposes the motion of the object and is influenced by the object’s shape, speed, and the properties of the fluid.

Question 32

Why do we use roller trolleys to pull trolley luggage?

• Roller trolleys reduce friction between the luggage and the ground, making it easier to move heavy luggage. The wheels allow for smooth movement, requiring less force to pull the luggage compared to dragging it directly on the ground.

Question 33

Write two methods for increasing friction.

1. Increasing the surface roughness: By using materials with rough surfaces, such as sandpaper or rubber, friction can be increased.
2. Applying more force: Increasing the weight or normal force pressing the two surfaces together can increase friction.

Question 34

Write any two situations where friction is experienced.

1. Walking: Friction between the soles of shoes and the ground prevents slipping and allows us to walk.
2. Driving a car: Friction between the tires of the car and the road surface allows the vehicle to accelerate, decelerate, and turn.

Question 35

What is the name of the organ that produces sound in humans?

• The organ that produces sound in humans is called the larynx (commonly known as the voice box).

Question 36

What is the difference between noise and music?

• Noise is typically characterized as an unpleasant, unwanted, or chaotic sound that can be disruptive. Music, on the other hand, is a structured combination of sounds that is usually harmonious and pleasing to the ear, consisting of rhythm, melody, and pitch.

Question 37

Define one vibration.

• One vibration is a complete cycle of movement of an object from its equilibrium position to one extreme, back to the equilibrium, and then to the other extreme. It represents a repetitive motion around a central point.

Question 38

What are ultrasonics and infrasonics?

• Ultrasonics refers to sound waves with frequencies above the audible range of human hearing (greater than 20,000 Hz). They are used in applications such as cleaning, medical imaging, and pest control.
• Infrasonics refers to sound waves with frequencies below the audible range (less than 20 Hz). These low-frequency sounds can be produced by natural phenomena, such as earthquakes or waves, and can affect humans and animals.

Question 39

Name the unit for measuring loudness and pitch.

• The unit for measuring loudness is the decibel (dB).
• The unit for measuring pitch is hertz (Hz), which measures the frequency of sound waves.

Question 40

What is the relation between frequency and time period?

• The frequency (f) and the time period (T) of a wave are inversely related. This relationship is expressed by the formula:
  [
  f = \frac{1}{T}
  ]
  or
  [
  T = \frac{1}{f}
  ]
  where frequency is the number of cycles per second, and the time period is the duration of one cycle.

Question 41

What is LED?

• LED stands for Light Emitting Diode. It is a semiconductor device that emits light when an electric current passes through it. LEDs are widely used in lighting, displays, and as indicator lights due to their energy efficiency and long lifespan.

Question 42

Define electric current.

• Electric current is the flow of electric charge, typically measured in amperes (A). It is the movement of electrons through a conductor, such as a wire, and can be classified as direct current (DC) or alternating current (AC).

Question 43

What is a conductor? Give an example.

• A conductor is a material that allows the flow of electric charge (electric current) easily due to the presence of free electrons. An example of a conductor is copper.

Question 44

Give two examples of electrolytes.

1. Sodium chloride (NaCl) – Common table salt, which dissociates into sodium and chloride ions in solution.
2. Potassium chloride (KCl) – A salt that dissociates into potassium and chloride ions in solution.

Question 45

Name the instrument used to detect current flowing through a wire.

• The instrument used to detect current flowing through a wire is an ammeter.

Question 46

What is an Epidemic?

• An epidemic is an outbreak of a disease that occurs when the number of cases of a disease exceeds what is normally expected in a particular geographic area or population over a specific period of time.

Question 47

Define Wind.

• Wind is the movement of air from an area of high pressure to an area of low pressure. It is caused by the uneven heating of the Earth’s surface by the sun, leading to variations in temperature and pressure.

Question 48

Where do the cyclones originate which hit the west coast of India?

• Cyclones that hit the west coast of India typically originate in the Arabian Sea.

Question 49

Name two methods to charge an uncharged object.

1. Conduction – Charging by direct contact, where electrons are transferred from one object to another.
2. Induction – Charging without direct contact, where a charged object is brought near an uncharged object, causing a redistribution of charges within the uncharged object.

Question 50

Define epicenter of an earthquake.

• The epicenter of an earthquake is the point on the Earth’s surface directly above the location where the earthquake originates (the focus or hypocenter). It is often where the strongest shaking is felt.

Question 51

Define opaque body.

• An opaque body is an object that does not allow light to pass through it. This means that no light is transmitted, and the object cannot be seen through; instead, it reflects or absorbs light. Examples include wood and metals.

Question 52

What is a mirror?

• A mirror is a reflective surface, typically made of glass coated with a metallic layer, that reflects light to form an image of whatever is in front of it. Mirrors are commonly used for viewing oneself, in optical devices, and in various applications in science and technology.

Question 53

What are nocturnal animals?

• Nocturnal animals are species that are active during the night and rest during the day. They have adaptions that allow them to see and hunt in low-light conditions. Examples include owls, bats, and raccoons.

Question 54

How can visually challenged persons read and write?

• Visually challenged persons can read and write using tools such as Braille, a tactile writing system where raised dots represent letters and numbers. They may also use assistive technology like screen readers and audio books to access written content.

Question 55

Name two organisms whose eyes have multiple lenses.

1. Insects (such as flies and bees) – They have compound eyes composed of thousands of tiny lenses called ommatidia.
2. Crustaceans (such as shrimp and crabs) – They also possess compound eyes with multiple lenses that help them detect motion and shapes.

Question 56

What is a weed? Write the names of two weeds and one method of removing them.

• A weed is an unwanted plant that competes with cultivated plants for nutrients, space, and light. They can be invasive and hinder agricultural productivity.
  Two examples of weeds:

1. Dandelion (Taraxacum officinale)
2. Crabgrass (Digitaria spp.)
   Method of removing them:

• Weeding (manual removal of weeds by pulling them out, including their roots) or using herbicides specifically designed to target weeds.

Question 57

What is Hybridization? How is it useful?

• Hybridization is the process of breeding two different varieties or species of organisms to create a hybrid, which often has desirable traits from both parents. It is useful in agriculture and horticulture to develop crops with improved characteristics, such as higher yield, pest resistance, or environmental adaptability.

Question 58

What is Biofertilizers?

• Biofertilizers are natural fertilizers that contain living microorganisms, which enhance the nutrient content of the soil and promote plant growth. They help in nutrient cycling, soil fertility, and are often more sustainable than chemical fertilizers. Common examples include Rhizobium, mycorrhizal fungi, and certain nitrogen-fixing bacteria.

Question 59

What are the different methods of sowing seeds?

1. Broadcasting: Scattering seeds evenly over the soil surface.
2. Row sowing: Planting seeds in rows at a specific spacing, which makes it easier to manage and harvest.
3. Transplanting: Pre-growing seeds in a nursery and then transferring the seedlings to the desired location.
4. Drilling: Using a seed drill to place seeds at a uniform depth and spacing in the soil.

Question 60

What do you mean by transplantation?

• Transplantation refers to the process of moving a plant or seedling from one location or medium (such as a nursery or pot) to another, usually into the ground or a larger container. This is often done to give the plant more space to grow, improve its chances of survival, or to manage the establishment of crops.

Question 61

What is a pest? Give examples.

• A pest is any organism that is considered harmful to crops, livestock, or humans. Pests can cause damage to plants, spread diseases, and interfere with human activities.
  Examples of pests:

1. Locusts – Insects that can swarm and cause devastation to crops.
2. Cockroaches – Pest insects that can contaminate food and spread disease.
3. Weeds – Undesirable plants that compete with cultivated crops for resources.

Question 62

What are viruses? Name three diseases caused by viruses.

• Viruses are microscopic pathogens that can only reproduce inside living host cells. They consist of genetic material (DNA or RNA) encased in a protein coat and can infect various types of organisms.
  Three diseases caused by viruses:

1. Influenza (Flu)
2. HIV/AIDS
3. COVID-19 (caused by the SARS-CoV-2 virus)

Question 63

What are various varieties of coal?

• The various varieties of coal, classified based on carbon content and usage, include:

1. Anthracite – Hard, high carbon content, and burns clean with high energy output.
2. Bituminous – The most common type, used for electricity generation and steel production.
3. Sub-bituminous – Lower carbon content than bituminous, used primarily for electricity generation.
4. Lignite – Brown coal with the lowest carbon content, used for electricity generation in power plants.

Question 64

What are exhaustible natural resources? Give examples.

• Exhaustible natural resources are resources that are finite and can be depleted when used excessively. They cannot be replenished in a human timeframe.
  Examples:

1. Coal
2. Oil
3. Natural gas
4. Minerals (like copper and iron)

Question 65

How are various products of coal obtained?

• Various products of coal are obtained through processes such as:

1. Coal gasification – Converting coal into gas (syngas).
2. Pyrolysis – Heating coal in the absence of air to produce coke, coal tar, and coal gas.
3. Carbonization – Producing coke, a porous carbon used in steel-making.
4. Coke manufacturing – Heating bituminous coal to drive off volatile compounds, leaving solid coke.

Question 66

Why is natural gas called cleaner fuel?

• Natural gas is considered a cleaner fuel because, when burned, it emits significantly lower amounts of harmful pollutants such as sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and particulate matter compared to other fossil fuels like coal and oil. It primarily produces carbon dioxide (CO₂) and water vapor, which contribute less to air pollution and climate change.

Question 67

Write some harmful effects of burning fossil fuels.

1. Air Pollution: Emission of pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter can lead to respiratory problems and environmental issues.
2. Greenhouse Gas Emissions: Burning fossil fuels contributes to carbon dioxide emissions, which is a significant factor in global warming and climate change.
3. Acid Rain: Pollutants from fossil fuels can lead to acid rain, which harms the environment, ecosystems, and infrastructure.
4. Health Issues: Prolonged exposure to air pollution is linked to various health problems, including asthma, lung cancer, and cardiovascular diseases.

Question 68

Water is not used to control fires involving electrical equipment. Why?

• Water conducts electricity, and using it on electrical fires can create a risk of electric shock or electrocution. Additionally, water can lead to further electrical hazards, as it may allow electricity to travel through the water.

Question 69

Paper itself catches fire easily whereas a piece of paper wrapped around an aluminum pipe does not. Why?

• Paper catches fire easily because it has a low ignition temperature and a high surface area, allowing it to ignite quickly. However, when wrapped around an aluminum pipe, the heat from the fire may be conducted away by the metal, preventing the paper from reaching its ignition temperature. Additionally, the aluminum can provide a barrier that limits airflow to the paper, reducing combustion.

Question 70

Name the unit to measure the calorific value of fuel.

• The calorific value of fuel is typically measured in Megajoules per kilogram (MJ/kg) or kilocalories per kilogram (kcal/kg). In some contexts, it can also be expressed in British Thermal Units (BTUs).

Here are the answers to your questions:

Question 71

What do you understand by deforestation and reforestation?

• Deforestation is the large-scale removal of forest or tree cover from a land area, leading to ecological imbalances and loss of biodiversity. It is often driven by agricultural expansion, logging, urbanization, and infrastructure development.
• Reforestation is the process of replanting trees in an area where forest cover has been reduced or destroyed. It aims to restore ecosystems, combat climate change, and improve biodiversity by re-establishing forested areas.

Question 72

How does a wildlife sanctuary help in the conservation of wildlife?

• A wildlife sanctuary provides a protected area where animals can live and thrive without the threat of poaching, habitat destruction, or human encroachment. Sanctuaries often promote breeding programs for endangered species, habitat restoration, research, and environmental education. By conserving natural habitats, wildlife sanctuaries support biodiversity and help maintain healthy ecosystems.

Question 73

Write three causes for the extinction of animals.

1. Habitat Loss: Destruction of natural habitats due to human activities such as deforestation, urbanization, and agriculture.
2. Pollution: Contamination of air, water, and soil can harm wildlife and disrupt ecosystems, leading to population declines.
3. Overexploitation: Unsustainable hunting, fishing, and trade can deplete animal populations faster than they can recover, pushing species towards extinction.

Question 74

What is cell division?

• Cell division is the process by which a parent cell divides into two or more daughter cells. It is essential for growth, development, and maintenance of all living organisms. There are two main types of cell division: mitosis, which is responsible for growth and repair, producing two identical daughter cells, and meiosis, which is involved in sexual reproduction, producing four genetically diverse gametes.

Question 75

Write the difference between asexual reproduction and sexual reproduction.

Aspect	Asexual Reproduction	Sexual Reproduction
Definition	Involves a single parent producing offspring.	Involves two parents contributing genetic material to offspring.
Genetic Variation	Offspring are genetically identical to the parent (clones).	Offspring have genetic variation due to the combination of genes from both parents.
Examples	Binary fission in bacteria, budding in yeast.	Fertilization in plants and animals, such as humans.
Speed	Generally faster; can quickly colonize an area.	Usually slower; requires finding a mate and completion of fertilization.

Question 76

Why is reproduction important?

• Reproduction is vital for the continuation of species. It ensures the survival of genetic material across generations, promotes genetic diversity (which helps populations adapt to changing environments), and enables organisms to replace those that die, maintaining population stability. Ultimately, reproduction is fundamental for the evolution and sustainability of life on Earth.

Question 77

What is binary fission?

• Binary fission is a type of asexual reproduction in which a single organism divides into two genetically identical daughter cells. This process is common in unicellular organisms like bacteria and amoebas. During binary fission, the organism duplicates its genetic material and then splits into two parts, each receiving a copy of the original DNA.

Question 78

How does Hydra reproduce?

• Hydra primarily reproduces asexually through a process called budding, where a new individual develops from a small outgrowth (bud) on the parent’s body. The bud grows and eventually detaches to become a separate organism. Hydra can also reproduce sexually, producing gametes that lead to the formation of a zygote.

Question 79

Explain the difference between viviparous and oviparous animals.

Aspect	Viviparous Animals	Oviparous Animals
Definition	Animals that give birth to live young. The embryos develop inside the mother’s body and receive nourishment from her.	Animals that lay eggs outside their bodies, with the embryos developing and hatching from those eggs.
Examples	Humans, dogs, and most mammals.	Birds, reptiles, and most insects.
Development	Internal development, usually with a placenta.	External development in eggs.

Question 80

How does fertilization occur in a frog?

• In frogs, fertilization occurs externally. The female frog lays eggs in water, and the male frog releases sperm over the eggs. The sperm then penetrates the eggs, leading to fertilization. Once fertilized, the eggs develop into embryos, eventually hatching into tadpoles.

Question 81

Differentiate between menopause and menarche.

Aspect	Menopause	Menarche
Definition	The time in a woman’s life (typically around age 50) when menstrual cycles permanently cease.	The first occurrence of menstruation in a female, marking the beginning of reproductive capability.
Age Range	Usually occurs between ages 45 and 55.	Usually occurs between ages 9 and 16.
Hormonal Changes	Associated with a decrease in estrogen and progesterone levels.	Initiated by hormonal changes, including increased levels of estrogen and progesterone.

Question 82

Why do adolescents get acne and pimples on the face at the time of puberty?

• During puberty, hormonal changes occur, particularly an increase in androgens. These hormones stimulate the sebaceous (oil) glands to produce more oil, which can clog pores and lead to the growth of bacteria. This results in acne and pimples on the face and other areas.

Question 83

Why is physical exercise important for adolescents?

• Physical exercise is important for adolescents for several reasons:

1. Physical Health: It promotes healthy growth and development, helps maintain a healthy weight, and reduces the risk of chronic diseases.
2. Mental Health: Exercise can improve mood, reduce stress, and enhance academic performance by boosting concentration and cognitive function.
3. Social Skills: Participating in sports and physical activities helps adolescents develop teamwork, communication, and social skills.

Question 84

Give two examples of contact force and non-contact force.

• Contact Forces:

1. Frictional Force – The resistance that occurs when two surfaces slide or attempt to slide across each other.
2. Tension Force – The force carried along a rope, cable, or string when it is pulled tight.

• Non-contact Forces:

1. Gravitational Force – The attraction between two masses, such as the Earth and an object.
2. Electrostatic Force – The attractive or repulsive force between charged objects.

Question 85

What is the force of friction?

• The force of friction is the resistance that one surface or object encounters when moving over another. It acts in the opposite direction of motion and can affect the acceleration and velocity of moving objects. Friction can be influenced by the nature of the surfaces in contact and the normal force between them.

Question 86

What is electrostatic force?

• Electrostatic force is the attraction or repulsion between charged particles. Like charges repel each other, while opposite charges attract. This force is responsible for various phenomena, such as static electricity and the behavior of charged objects in electric fields.

Question 87

Explain the difference between contact and non-contact forces.

Aspect	Contact Forces	Non-contact Forces
Definition	Forces that require physical contact between objects.	Forces that act over a distance without physical contact.
Examples	Friction, tension, and normal force.	Gravitational force, electrostatic force, and magnetic force.

Question 88

How does the atmosphere save us from shooting stars?

• The atmosphere acts as a protective shield for Earth, causing most meteoroids (commonly referred to as shooting stars) to burn up due to the friction they encounter as they enter at high speeds. This results in a light display as they incinerate before reaching the surface.

Question 89

Why are ships, boats, and airplanes made streamlined?

• Ships, boats, and airplanes are designed with streamlined shapes to reduce drag and resistance when moving through water or air. A streamlined shape allows these vehicles to move more efficiently, improving speed and fuel efficiency while facilitating smoother movement through their respective mediums.

Question 90

Why do we rub our hands in winter?

• We rub our hands together in winter to create friction, which generates heat through the movement of the surfaces against each other. This frictional heat helps warm our hands and provides comfort against the cold temperature.

Question 91

A pendulum oscillates 50 times in 5 seconds. Find its time period and frequency.

• Frequency (f) is calculated as the number of oscillations per second.
  [
  f = \frac{\text{Number of oscillations}}{\text{Time in seconds}} = \frac{50 \text{ oscillations}}{5 \text{ seconds}} = 10 \text{ Hz}
  ]
• Time Period (T) is the reciprocal of frequency.
  [
  T = \frac{1}{f} = \frac{1}{10 \text{ Hz}} = 0.1 \text{ seconds}
  ]

Question 92

The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of vibration?

• The time period (T) is the reciprocal of the frequency (f).
  [
  T = \frac{1}{f} = \frac{1}{500 \text{ Hz}} = 0.002 \text{ seconds} \text{ or } 2 \text{ milliseconds}
  ]

Question 93

What is the audible and inaudible frequency range for humans?

• Audible Frequency Range: Approximately 20 Hz to 20,000 Hz (20 kHz).
• Inaudible Frequency Range: Frequencies below 20 Hz are referred to as infrasound, while frequencies above 20 kHz are referred to as ultrasound.

Question 94

Define the following.

1. Loudness: Loudness is the perception of the intensity of a sound by the human ear, which is influenced by the sound’s amplitude. It is measured in decibels (dB).
2. Pitch: Pitch is the perceived frequency of a sound, determining how high or low a sound seems to the human ear. It is influenced by the frequency of vibration; higher frequencies correspond to higher pitches, and lower frequencies correspond to lower pitches.
3. Quality or Timbre: Quality, or timbre, refers to the unique characteristics of a sound that distinguish it from others, even if they have the same pitch and loudness. It is determined by the harmonic content and the sound wave’s complexity.

Question 95

How can pure water be made an electrolyte?

• Pure water is a poor conductor of electricity. To make it an electrolyte, a soluble ionic compound, such as salt (sodium chloride), can be dissolved in it. This dissociation produces ions, which carry electric current.

Question 96

Draw a labeled diagram of an electric tester.
Unfortunately, I can’t draw in this text environment, but I can describe it for you.

• Electric Tester Diagram:
• A simple electric tester often consists of:
  • A bulb (LED or incandescent) that lights up to indicate current flow.
  • Wires connecting to the bulb.
  • Probes at the ends of the wires for touching the electronic component or circuit to be tested.

Please refer to a textbook or online resource for an exact visual representation.

Question 97

Why do electricians wear rubber gloves and rubber shoes?

• Electricians wear rubber gloves and rubber shoes because rubber is an insulator. It prevents electric current from passing through and protects electricians from electrical shocks while they work on live wires or circuits.

Question 98

What is a pandemic? Name any two pandemics.

• A pandemic is an outbreak of a disease that occurs on a global scale, affecting a large number of people and spreading across multiple countries or continents.
• Two Examples of Pandemics:
  1. The 1918 Influenza Pandemic (Spanish Flu).
  2. The COVID-19 Pandemic (caused by the coronavirus SARS-CoV-2).

Question 100

Draw the labeled diagram of a gold leaf electroscope and give its construction.
Again, I can’t provide visual drawings here, but I can describe it.

• Gold Leaf Electroscope Diagram Overview:
  • A metal rod connected to a pair of gold leaves suspended from the bottom of the rod.
  • A glass or plastic container holds the setup to prevent air currents from affecting it.
  • A metal base that connects to the ground.

Construction:

1. The electroscope consists of a metal rod that is fixed vertically, with the top connected to a conductor.
2. The gold leaves, usually extremely thin, hang from the bottom of the rod.
3. When the top conductor is electrically charged, it induces a charge on the gold leaves, causing them to repel each other due to like charges.

Question 101

Write any three safety measures during lightning.

1. Seek Shelter: Stay indoors or seek cover in a sturdy building or a car to avoid being outdoors during a thunderstorm.
2. Avoid Electrical Appliances: Do not use wired phones, computers, or electrical appliances during a lightning storm to reduce the risk of electric shock.
3. Stay Away from Open Fields and Tall Objects: Avoid open spaces, trees, and metal objects, as they can attract lightning. If caught outside, crouch low to the ground and minimize contact with it.

Question 102

How does a Seismograph work?
A seismograph is an instrument used to measure and record the motion of the ground during an earthquake. It works on the principle of inertia. When an earthquake occurs, the ground shakes, causing the base of the seismograph to move. The suspended mass (or pendulum) tends to remain still due to inertia. As the base moves, the relative motion between the mass and the base is recorded on a rotating drum or digital display, creating a seismogram. The seismogram shows the amplitude and frequency of the seismic waves which help in analyzing the earthquake’s size and impact.

Question 103

What is Newton’s disc?
Newton’s disc is a circular disk divided into segments of different colors corresponding to the colors of the spectrum (red, orange, yellow, green, blue, indigo, violet). When spun rapidly, the colors blend together due to the persistence of vision, creating the illusion of white light. This demonstration illustrates how white light is made up of various colors and was part of Isaac Newton’s experiments with light and color.

Question 104

Write all the colours of the spectrum of white light in sequence.
The colors of the spectrum of white light, in order, are:

1. Red
2. Orange
3. Yellow
4. Green
5. Blue
6. Indigo
7. Violet

Question 105

What is persistence of vision?
Persistence of vision is a phenomenon where the human eye retains an image for a brief moment after the source of the image has disappeared. This effect allows us to perceive a series of rapidly changing images as a continuous motion, which is the principle behind movies, animations, and even the operation of devices like the zoetrope.

Question 106

In which state of India is the largest coal mine located?
The largest coal mine in India is located in the state of Jharkhand. The Jharia coalfield in Jharkhand is one of the largest coal reserves in the country and is known for its vast quantity of high-quality coal.

Question 107

Define vaccination; name three diseases that can be prevented through vaccination.
Vaccination is the process of administering a vaccine to stimulate an individual’s immune system to develop adaptive immunity against a specific pathogen. Vaccines contain an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the pathogen, its toxins, or one of its surface proteins.

Three diseases that can be prevented through vaccination:

1. Measles
2. Polio
3. Hepatitis B

Question 108

What do you mean by carbonisation?
Carbonisation is the process of converting organic material into carbon or carbon-rich residue through the application of heat in the absence of oxygen (pyrolysis). During carbonisation, volatile substances are released, and what remains is carbon-rich material that can be used as fuel (e.g., charcoal) or in other industrial applications.

Question 109

What is the difference between endangered species and extinct species?

• Endangered Species: These are species that are at risk of extinction in the near future due to a decline in their population or habitat. Efforts are often made to conserve and protect these species to prevent extinction.
• Extinct Species: These are species that no longer exist anywhere on Earth. Extinction means that there are no living individuals of the species remaining, either in the wild or in captivity.

Question 110

What is the Red Data Book?
The Red Data Book is a comprehensive reference work that provides information on the conservation status of various wildlife species. It lists species that are threatened with extinction, categorizing them into various levels of risk, such as vulnerable, endangered, and critically endangered. The book serves as a crucial tool for conservationists and researchers to monitor and protect biodiversity.

Question 111

It is difficult to burn green leaves, but dry leaves catch fire easily. Explain.
Green leaves contain a significant amount of water and other substances such as chlorophyll, which makes them difficult to ignite. The moisture content prevents combustion, as a higher temperature is needed to evaporate the water before combustion occurs. In contrast, dry leaves have lower moisture content and are more easily ignited due to their light and porous structure, which allows for better airflow and quicker heat generation, making combustion easier.

Question 112

What is menstruation? Explain.
Menstruation is a monthly biological process in which the lining of the uterus (endometrium) thickens in preparation for a potential pregnancy. If fertilization does not occur, this lining sheds and is expelled from the body through the vagina, along with blood and mucus, resulting in what is known as a menstrual period. Menstruation typically lasts between 3 to 7 days and is part of the menstrual cycle, which is regulated by hormones. It signifies fertility and the reproductive health of individuals with a uterus.

Question 113

What is gravitational force?
Gravitational force is the attractive force that pulls objects towards one another due to their mass. It is one of the four fundamental forces of nature and is responsible for the attraction between celestial bodies, such as planets, stars, and moons, as well as objects on Earth. The strength of the gravitational force between two masses depends on their masses and the distance between them, as described by Newton’s Law of Universal Gravitation. On Earth, the gravitational force gives weight to physical objects and governs motion in our daily lives.