Pedagogy

CTET Science MCQ with Answers, Paper 2

353 practice questions on Science and its Pedagogy (Paper II) for CTET Paper II (Mathematics and Science), with answers; most also have an explanation or a worked solution. Try each one before you open its answer.

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1. Q.151

   Which of the following pairs of a plant and the usual means of dispersal of its seeds is NOT correctly matched?

   1. A Coconut – water
   2. B Xanthium – wind
   3. C Drumstick – wind
   4. D Castor – bursting of the fruit
   Show answer

   Correct answer: (B) Xanthium – wind

   Xanthium fruits have spines and hooks that cling to the fur of animals, so its seeds are dispersed by animals. Coconut floats on water, drumstick seeds are winged and carried by wind, and castor fruits burst to scatter their seeds.

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2. Q.152

   The handles of frying pans and pressure cookers are made of bakelite. The main reason is that bakelite is:

   1. A A thermoplastic that softens easily on heating
   2. B A metal that is a good conductor of heat
   3. C A natural fibre that does not burn at all
   4. D A thermosetting plastic and a poor conductor of heat
   Show answer

   Correct answer: (D) A thermosetting plastic and a poor conductor of heat

   Bakelite is a thermosetting plastic: once moulded it does not soften on heating, and it is a poor conductor of heat and electricity. That is why it is used for handles of utensils and for electrical switches.

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3. Q.153

   To find out whether sugar dissolves faster in hot water, a student puts one spoon of sugar in 100 mL of hot water and two spoons of sugar in 50 mL of cold water. What is wrong with this investigation?

   1. A Sugar should never be used in experiments about how substances dissolve
   2. B Temperature cannot affect how fast a substance dissolves
   3. C More than one factor has been changed, so it is not a fair test
   4. D The student should have used only cold water in both
   Show answer

   Correct answer: (C) More than one factor has been changed, so it is not a fair test

   In a fair test only the factor being investigated, here temperature, is changed; the amount of sugar and the volume of water must stay the same. Because three things changed at once, any difference cannot be linked to temperature.

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4. Q.154

   Match the scientist in List I with the contribution in List II.

   List I: A. Alexander Fleming B. Edward Jenner C. Robert Koch D. Louis Pasteur

   List II: 1. Proving that a bacterium causes anthrax 2. Penicillin 3. Vaccine for smallpox 4. Showing that microorganisms cause fermentation

   1. A A-3, B-2, C-4, D-1
   2. B A-2, B-1, C-3, D-4
   3. C A-4, B-3, C-1, D-2
   4. D A-2, B-3, C-1, D-4
   Show answer

   Correct answer: (D) A-2, B-3, C-1, D-4

   Fleming found penicillin, produced by a mould; Jenner developed the vaccine for smallpox; Koch proved that a bacterium (Bacillus anthracis) causes anthrax; and Pasteur showed that fermentation is brought about by microorganisms.

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5. Q.155

   A group of students is caught in an open field when lightning starts. There is no building or vehicle nearby. What should they do?

   1. A Squat low, with hands on the knees and head between the hands
   2. B Lie flat on the ground with their arms and legs stretched out
   3. C Take shelter under the tallest isolated tree in the field
   4. D Stand still and hold an open umbrella above their heads
   Show answer

   Correct answer: (A) Squat low, with hands on the knees and head between the hands

   In the open, one should squat low, placing the hands on the knees and the head between the hands, so as to be the smallest target. Lying flat, standing under an isolated tall tree or holding an umbrella is unsafe.

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6. Q.156

   In a practical class, students follow numbered steps on a worksheet and fill in blanks whose answers the sheet already hints at. To make this more inquiry-based, the teacher should:

   1. A Pose a question and let students plan how to test it, predict, and explain their results
   2. B Replace the practical work with reading the textbook aloud
   3. C Give the expected results in advance so that time is saved
   4. D Add many more numbered steps to the worksheet so that no student can possibly make a mistake
   Show answer

   Correct answer: (A) Pose a question and let students plan how to test it, predict, and explain their results

   'Cookbook' practicals, where students follow fixed steps to reach a known answer, develop little thinking. Turning them into investigations in which students plan, predict, test and explain uses the process skills that inquiry teaching aims at.

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7. Q.157

   Assertion (A): Water should not be used to put out a fire involving oil or petrol.

   Reason (R): Water is heavier than oil, so it sinks below the oil and the oil keeps burning on top.

   Choose the correct option.

   1. A Both A and R are true, and R is the correct explanation of A
   2. B Both A and R are true, but R is not the correct explanation of A
   3. C A is true, but R is false
   4. D A is false, but R is true
   Show answer

   Correct answer: (A) Both A and R are true, and R is the correct explanation of A

   Both statements are true and R explains A. For fires involving oil, petrol or electrical equipment, carbon dioxide is a better extinguisher, because it covers the fire like a blanket and cuts off its contact with oxygen.

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8. Q.158

   It takes more effort to start moving a heavy box across the floor than to keep it moving once it has started. Why?

   1. A Sliding friction is slightly greater than static friction
   2. B Static friction is slightly greater than sliding friction
   3. C The box becomes lighter once it starts to move
   4. D Friction acts on the box only while it is at rest
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   Correct answer: (B) Static friction is slightly greater than sliding friction

   Before the box moves, the irregularities of the two surfaces interlock firmly and static friction must be overcome. Once it slides, the interlocking is less, so sliding friction is a little smaller; friction does not disappear.

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9. Q.159

   The leaves of a plant show parallel venation, as in grass or wheat. What type of roots is this plant most likely to have?

   1. A A tap root with smaller lateral roots
   2. B Roots growing out from the margins of the leaves
   3. C Fibrous roots arising from the base of the stem
   4. D A single thick root with no branches at all
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   Correct answer: (C) Fibrous roots arising from the base of the stem

   Plants whose leaves have parallel venation generally have fibrous roots, while plants with reticulate venation generally have a tap root with lateral roots. Grass, wheat and maize have fibrous roots.

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10. Q.160

    Muddy water is left undisturbed in a glass until the mud settles at the bottom, and then the clear water above is gently poured into another glass. The two processes used, in order, are:

    1. A Sedimentation and decantation
    2. B Decantation and filtration
    3. C Evaporation and condensation
    4. D Filtration and sedimentation
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    Correct answer: (A) Sedimentation and decantation

    The settling of the heavier insoluble mud is sedimentation, and pouring off the clear liquid without disturbing the sediment is decantation. Filtration would need a filter such as filter paper.

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11. Q.161

    Which statement about a 'test-tube baby' is correct?

    1. A The baby develops fully inside a test tube in a laboratory
    2. B Fertilisation is outside the body; the baby grows in the mother's uterus
    3. C Fertilisation takes place inside the body, but the baby develops in a test tube
    4. D The baby is produced from a single parent without any fertilisation
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    Correct answer: (B) Fertilisation is outside the body; the baby grows in the mother's uterus

    In in vitro fertilisation the egg and sperms are brought together outside the body; the early embryo is then placed in the mother's uterus, where complete development takes place. The name 'test-tube baby' is therefore misleading.

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12. Q.162

    Match List I with List II:

    List I: (A) Ursa Major (B) Orion (C) Cassiopeia (D) Sirius

    List II: (1) Looks like a distorted letter W or M (2) Also called the Great Bear; its seven bright stars form the Saptarishi (3) Also called the Hunter; its three middle stars form his belt (4) The brightest star in the night sky

    1. A A-2, B-3, C-1, D-4
    2. B A-3, B-2, C-1, D-4
    3. C A-2, B-3, C-4, D-1
    4. D A-1, B-3, C-2, D-4
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    Correct answer: (A) A-2, B-3, C-1, D-4

    Ursa Major is the Great Bear, and its seven bright stars form the Saptarishi (Big Dipper); Orion is also called the Hunter, its three middle stars forming his belt; Cassiopeia looks like a distorted W or M; and Sirius, the brightest star in the night sky, lies close to Orion.

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13. Q.163

    Which test item best assesses the process skill of controlling variables?

    1. A 'Riya tests if salt water speeds up rusting. What must she keep the same in both tubes?'
    2. B 'Draw a neat diagram of a test tube held in a stand, and label each of its parts clearly.'
    3. C 'Name two conditions that are needed for iron to rust.'
    4. D 'Define rusting in your own words.'
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    Correct answer: (A) 'Riya tests if salt water speeds up rusting. What must she keep the same in both tubes?'

    Controlling variables means identifying the factors that must be kept constant so that only the factor being tested changes. The item about Riya's test tubes asks exactly that; the others test recall, drawing or understanding of a term.

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14. Q.164

    Porters at railway stations often place a round, folded piece of cloth on their heads before lifting a heavy load. This helps because the cloth:

    1. A Reduces the weight of the load that is being carried
    2. B Increases the area of contact, so the pressure on the head is less
    3. C Increases the pressure on the head so the load stays steady
    4. D Reduces the force of gravity that acts on the load
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    Correct answer: (B) Increases the area of contact, so the pressure on the head is less

    Pressure is force per unit area. The cloth spreads the same weight over a larger area of the head, so the pressure, and the discomfort, is less; the weight of the load does not change.

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15. Q.165

    Consider the following statements about children's alternative conceptions in science:

    1. They often arise from everyday experience and make sense from the child's point of view.

    2. They are usually held by only one or two children in a class.

    Which of the statements is/are correct?

    1. A Only 1
    2. B Only 2
    3. C Both 1 and 2
    4. D Neither 1 nor 2
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    Correct answer: (A) Only 1

    Alternative conceptions are built from everyday experience and language and seem sensible to the child, so they deserve to be taken seriously. Research shows that the same conceptions are commonly shared by many learners, even in different countries, so statement 2 is wrong.

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16. Q.166

    At the end of each activity, students write in a journal what they understood, what confused them and what they will try next. This practice is best described as:

    1. A Assessment of learning
    2. B Summative assessment
    3. C Assessment as learning
    4. D Norm-referenced testing
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    Correct answer: (C) Assessment as learning

    In assessment as learning, students monitor and reflect on their own learning, which builds self-regulation. Assessment of learning is a summative judgement made at the end of a period of teaching.

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17. Q.167

    Match the feature (List I) with how it helps the animal (List II):

    A. Long ears of a deer

    B. Eyes on the sides of a deer's head

    C. Light brown colour of a lion

    D. Eyes in front of a lion's face

    1. Helps it hide in dry grass while hunting

    2. Gives a correct idea of where its prey is

    3. Lets it look in all directions for danger

    4. Picks up the movements of predators

    1. A A-3, B-4, C-2, D-1
    2. B A-4, B-2, C-1, D-3
    3. C A-1, B-3, C-4, D-2
    4. D A-4, B-3, C-1, D-2
    Show answer

    Correct answer: (D) A-4, B-3, C-1, D-2

    A deer's long ears pick up the movements of predators and its eyes on the sides of the head let it look in all directions. A lion's light brown colour helps it hide in dry grass, and its eyes in front give a correct idea of where its prey is.

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18. Q.168

    Two students measure the length of the same table with their handspans. One gets 9 handspans and the other 10. The main reason for the difference is that:

    1. A One of the two students must have counted the number of handspans wrongly
    2. B A handspan differs from person to person, so it is not a standard unit
    3. C The length of the table changed between the two measurements
    4. D Handspans are suitable only for measuring curved lengths
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    Correct answer: (B) A handspan differs from person to person, so it is not a standard unit

    Body-based units such as the handspan, cubit and footstep vary from person to person, so they give different results for the same length. This is why standard units such as the metre, accepted everywhere, are used.

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19. Q.169

    Most students in a Class 8 believe that a heavier stone falls faster than a lighter one. The most effective way for the teacher to address this misconception is to:

    1. A Tell them that Galileo proved long ago that this is wrong
    2. B Ignore it, as children will outgrow it on their own
    3. C Let them drop two balls of different mass from the same height at the same time and discuss what they observe
    4. D Mark the answer wrong in the test and move on to the next topic
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    Correct answer: (C) Let them drop two balls of different mass from the same height at the same time and discuss what they observe

    Misconceptions are resistant to mere assertion. Creating cognitive conflict through a direct experience that contradicts the belief, followed by discussion, helps the learner reconstruct the concept.

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20. Q.170

    Assertion (A): Dolphins and whales come up to the surface of the water from time to time.

    Reason (R): They do not have gills and breathe in air through blowholes (nostrils) on the upper part of the head.

    1. A Both A and R are true, and R is the correct explanation of A
    2. B Both A and R are true, but R is not the correct explanation of A
    3. C A is true, but R is false
    4. D A is false, but R is true
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    Correct answer: (A) Both A and R are true, and R is the correct explanation of A

    Dolphins and whales live in water but have no gills; they breathe air through blowholes on top of the head. So they must come to the surface from time to time to breathe, which is why R explains A.

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21. Q.171

    On a sunny day, many small round patches of light are seen on the ground under a tree with dense leaves, even though the gaps between the leaves have irregular shapes. These patches are:

    1. A Spots where the leaves focus the light as lenses do
    2. B Images of the Sun formed by the small gaps acting like pinholes
    3. C Reflections of the sky from the shiny surfaces of the leaves
    4. D Shadows of the round fruits hanging from the tree
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    Correct answer: (B) Images of the Sun formed by the small gaps acting like pinholes

    Each small gap between the leaves acts like a pinhole and forms an image of the Sun on the ground. Since the Sun is round, the images are round whatever the shape of the gaps.

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22. Q.172

    A turmeric (haldi) stain on a white shirt turns red when the shirt is washed with soap. The best explanation is:

    1. A Soap solution is acidic and turns turmeric red
    2. B Hot water used for washing changes the colour of turmeric
    3. C Soap reacts with the cotton to form a red dye
    4. D Soap solution is basic and turns turmeric red
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    Correct answer: (D) Soap solution is basic and turns turmeric red

    Turmeric is a natural indicator that turns red in a basic solution and stays yellow in acidic or neutral ones. Soap solution is basic, so the yellow stain turns red.

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23. Q.173

    Characteristics are passed on from parents to offspring by genes. Where in the cell are genes located?

    1. A In the plastids in the cytoplasm
    2. B On the chromosomes in the nucleus
    3. C On the outer surface of the cell membrane
    4. D Inside the large central vacuole
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    Correct answer: (B) On the chromosomes in the nucleus

    The nucleus contains thread-like chromosomes, which carry genes; the gene is the unit of inheritance that transfers characters from parents to offspring. The nucleus also controls the activities of the cell.

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24. Q.174

    Trees in cold mountain regions are often cone-shaped, with sloping branches and needle-like leaves. How does this help them?

    1. A Rainwater and snow slide off them easily
    2. B Their roots can grow deeper into frozen soil
    3. C They can store more water in their leaves
    4. D Grazing animals cannot reach their leaves
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    Correct answer: (A) Rainwater and snow slide off them easily

    The cone shape, sloping branches and needle-like leaves let rainwater and snow slide off easily.

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25. Q.175

    When a zinc granule is placed in blue copper sulphate solution, the blue colour fades and a brown deposit forms. A copper strip placed in zinc sulphate solution shows no change. This shows that:

    1. A Copper is more reactive than zinc
    2. B Zinc and copper are equally reactive
    3. C Zinc sulphate is more reactive than zinc
    4. D Zinc is more reactive than copper
    Show answer

    Correct answer: (D) Zinc is more reactive than copper

    A more reactive metal can displace a less reactive metal from its compound in solution, but not the other way round. Zinc displaces copper from copper sulphate, so zinc is more reactive than copper.

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26. Q.176

    A teacher compares an electric circuit with water flowing through a closed loop of pipes. To use this analogy well, the teacher should:

    1. A Avoid analogies altogether, since they always create misconceptions
    2. B Present the analogy to the class as an exact description of how electricity behaves
    3. C Ask students to memorise the analogy as the definition of electric current
    4. D Discuss which features match the real circuit and where the analogy breaks down
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    Correct answer: (D) Discuss which features match the real circuit and where the analogy breaks down

    Analogies link the unfamiliar to the familiar, but every analogy has limits; for example, nothing spills out when a wire is cut. Discussing where it fits and where it fails keeps the analogy from becoming a new misconception.

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27. Q.177

    Match the nutrient in List I with the disease caused by its deficiency in List II.

    List I: A. Vitamin A B. Vitamin B1 C. Vitamin D D. Iron

    List II: 1. Rickets 2. Anaemia 3. Beriberi 4. Loss of vision in the dark

    1. A A-4, B-3, C-1, D-2
    2. B A-3, B-4, C-2, D-1
    3. C A-4, B-1, C-3, D-2
    4. D A-2, B-3, C-1, D-4
    Show answer

    Correct answer: (A) A-4, B-3, C-1, D-2

    Vitamin A deficiency causes poor vision and loss of vision in the dark, vitamin B1 deficiency causes beriberi, vitamin D deficiency causes rickets (soft, bent bones), and iron deficiency causes anaemia.

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28. Q.178

    In a fast-growing town, open ground has been covered with concrete roads, pavements and buildings. Even with normal rainfall, the water table there keeps falling. The most likely reason is that:

    1. A Concrete soaks up groundwater from below the surface
    2. B The weight of the new buildings pushes the groundwater deeper down
    3. C Less rainwater seeps in, so groundwater is not recharged
    4. D Concrete makes rainwater evaporate before it falls
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    Correct answer: (C) Less rainwater seeps in, so groundwater is not recharged

    Groundwater is recharged when rainwater seeps into the ground through open soil. Concrete and other paved surfaces stop this, while drawing out of water continues, so the water table falls.

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29. Q.179

    Which statement correctly distinguishes a scientific law from a scientific theory?

    1. A Laws hold only inside laboratories, while theories hold in everyday life
    2. B A law is only an informed guess, while a theory is a fact that has been fully proved by experiments
    3. C A theory becomes a law once enough experiments have proved it to be true
    4. D A law describes what regularly happens in nature; a theory explains why it happens
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    Correct answer: (D) A law describes what regularly happens in nature; a theory explains why it happens

    A law states what regularly happens, while a theory explains why it happens; they are different kinds of knowledge. The idea that a theory 'grows into' a law once it is proved is a common misunderstanding about the nature of science.

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30. Q.180

    In the earlier series of NCERT science textbooks for Classes VI to VIII, two child characters, Paheli and Boojho, appear throughout. They mainly serve to:

    1. A Summarise each chapter for revision before the examinations
    2. B Model curiosity by raising the kind of questions children are likely to ask
    3. C Present the life stories of famous scientists
    4. D Provide the correct answers to the exercises given at the end of each chapter
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    Correct answer: (B) Model curiosity by raising the kind of questions children are likely to ask

    Paheli and Boojho voice the questions that curious children ask, encouraging learners to wonder, question and investigate rather than wait for ready-made answers.

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31. Q.181

    Which of the following practices does NOT help challenge the stereotype that science is mainly for boys?

    1. A Using gender-neutral language in worksheets and test questions
    2. B Including the work of women scientists such as the botanist E.K. Janaki Ammal in lessons
    3. C Using examples in which only boys build models and only girls help with the cooking
    4. D Using pictures that show both girls and boys doing experiments
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    Correct answer: (C) Using examples in which only boys build models and only girls help with the cooking

    Examples that show only boys doing technical work reinforce the stereotype. Women role models such as E.K. Janaki Ammal, a pioneering Indian botanist, balanced pictures and neutral language help every child see science as open to them.

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32. Q.182

    An earthworm moves more easily on a rough surface such as soil or rough paper than on a smooth glass plate. This is because:

    1. A Its bones and joints can bend properly only on rough surfaces
    2. B Its body releases less slime when it is on a rough surface
    3. C It has suckers on its head that stick only to rough surfaces
    4. D Tiny bristles under its body grip rough surfaces
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    Correct answer: (D) Tiny bristles under its body grip rough surfaces

    An earthworm has no bones; it moves by alternately stretching and contracting the muscles of its ringed body. Tiny bristles on the underside, connected with muscles, grip the ground, but on smooth glass they get no grip.

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33. Q.183

    Sunita has two identical-looking iron bars, only one of which is a magnet. Which observation proves for sure that a bar is a magnet?

    1. A One end of it repels an end of a known magnet
    2. B It attracts one end of a known magnet
    3. C It is attracted by both ends of a known magnet
    4. D It is heavier than the other iron bar
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    Correct answer: (A) One end of it repels an end of a known magnet

    A magnet attracts even an unmagnetised piece of iron, so attraction cannot tell the two bars apart. Repulsion happens only between like poles of two magnets, so it is the sure test.

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34. Q.184

    Students of Class 7 watch a candle burning under an inverted glass jar placed in a tray of water. Which of the following student statements is an INFERENCE rather than an observation?

    1. A The flame went out because the oxygen inside the jar was used up
    2. B The flame became smaller and smaller
    3. C The water level inside the jar rose
    4. D The flame went out after some time
    Show answer

    Correct answer: (A) The flame went out because the oxygen inside the jar was used up

    An observation is what the senses directly record (flame shrinking, flame going out, water rising). An inference is an explanation drawn from those observations, such as attributing the extinguished flame to the consumption of oxygen.

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35. Q.185

    Consider the following statements:

    1. Creepers are plants with weak stems that cannot stand upright and spread on the ground.

    2. Climbers are plants with thick, woody stems that stand upright without any support.

    Which of the statements given above is/are correct?

    1. A Only 1
    2. B Only 2
    3. C Both 1 and 2
    4. D Neither 1 nor 2
    Show answer

    Correct answer: (A) Only 1

    Statement 1 is correct. Statement 2 is wrong: climbers also have weak stems, but they take support on neighbouring structures and climb up; a thick woody stem that stands on its own is a feature of trees.

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36. Q.186

    In the circuit symbol of an electric cell, two parallel lines of unequal length are drawn. The longer line represents the:

    1. A Negative terminal
    2. B Switch in the 'on' position
    3. C Positive terminal
    4. D Filament of the bulb
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    Correct answer: (C) Positive terminal

    In the symbol of a cell, the longer line stands for the positive terminal and the shorter, thicker line for the negative terminal. A battery is shown by joining several such cell symbols.

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37. Q.187

    Which of the following teacher behaviours is MOST consistent with the inquiry approach to teaching science?

    1. A Asking 'What do you think will happen if we add salt to the water? How can we find out?'
    2. B Giving precise definitions and asking students to memorise them
    3. C Dictating notes on the topic from a reference book
    4. D Demonstrating the experiment and asking students to copy the result
    Show answer

    Correct answer: (A) Asking 'What do you think will happen if we add salt to the water? How can we find out?'

    In inquiry, the teacher poses questions that invite students to predict, design investigations and find out for themselves. Definitions, dictation and copying results keep the learner passive.

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38. Q.188

    During a thunderstorm, electric charges in a cloud become separated. Where do they collect?

    1. A Positive charges near the upper edges, negative charges near the lower edges
    2. B Negative charges near the upper edges, positive charges near the lower edges
    3. C Both kinds of charge spread evenly throughout the whole cloud
    4. D All the charges leave the cloud at once and go into the ground
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    Correct answer: (A) Positive charges near the upper edges, negative charges near the lower edges

    Rising air currents and falling water droplets separate the charges: positive charges gather near the upper edges of the cloud and negative charges near the lower edges, and positive charges also collect near the ground. When the charges become very large, the air can no longer resist their flow and lightning occurs.

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39. Q.189

    Which of the following statements about viruses is correct?

    1. A They are larger than bacteria and fungi
    2. B They make their own food with the help of sunlight
    3. C They grow on bread and pickles like moulds
    4. D They reproduce only inside the cells of a host organism
    Show answer

    Correct answer: (D) They reproduce only inside the cells of a host organism

    Viruses are microscopic and reproduce only inside the cells of a host organism, which may be a bacterium, a plant or an animal. They cannot make food and do not grow on bread like moulds.

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40. Q.190

    Seeds stored in a dry jar for months show no growth, yet the same seeds sprout when given water, air and warmth. What does this show?

    1. A Seeds become living only after water is added
    2. B Seeds are non-living because they did not grow in the jar
    3. C Seeds are living only while attached to the parent plant
    4. D Seeds are living but need favourable conditions to grow
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    Correct answer: (D) Seeds are living but need favourable conditions to grow

    A seed is a living thing that stays inactive until it gets water, air and suitable warmth, and then it germinates. The same seed sprouting later shows it was alive all along; water did not make it living.

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41. Q.191

    Assertion (A): When we rub our palms together briskly for some time, they feel warm.

    Reason (R): Friction between two surfaces produces heat.

    1. A Both A and R are true, and R is the correct explanation of A
    2. B Both A and R are true, but R is not the correct explanation of A
    3. C A is true, but R is false
    4. D A is false, but R is true
    Show answer

    Correct answer: (A) Both A and R are true, and R is the correct explanation of A

    Rubbing the palms works against friction, and this produces heat, which is why the palms warm up; striking a matchstick works the same way. R correctly explains A.

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42. Q.192

    Which of the following human diseases is NOT caused by a virus?

    1. A Typhoid
    2. B Measles
    3. C Polio
    4. D Chicken pox
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    Correct answer: (A) Typhoid

    Typhoid is caused by bacteria and spreads through contaminated water. Measles, polio and chicken pox are viral diseases.

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43. Q.193

    Compared with the same amount of carbohydrates, fats give the body:

    1. A About the same energy
    2. B Much less energy
    3. C Much more energy
    4. D No energy, only body-building material
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    Correct answer: (C) Much more energy

    Both carbohydrates and fats are energy-giving foods, but fats give much more energy than the same amount of carbohydrates. Body-building is mainly the work of proteins.

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44. Q.194

    According to NCF 2005, the science textbook should be treated as:

    1. A The only authentic source of knowledge for the class
    2. B A document whose content is to be memorised for the examination
    3. C One of many resources for learning, supplemented by activities and the environment
    4. D Something to be replaced by guides and solved question banks
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    Correct answer: (C) One of many resources for learning, supplemented by activities and the environment

    NCF 2005 asks teachers to go beyond the textbook and treat it as one resource among activities, experiments, the local environment, library and ICT, rather than the sole authority to be memorised.

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45. Q.195

    Consider the following statements about magnets:

    1. A magnet can lose its magnetism if it is heated strongly.

    2. A magnet can lose its magnetism if it is hammered or dropped from a height again and again.

    Which of the statements given above is/are correct?

    1. A Only 1
    2. B Only 2
    3. C Both 1 and 2
    4. D Neither 1 nor 2
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    Correct answer: (C) Both 1 and 2

    Magnets lose their properties when heated, hammered or dropped repeatedly from a height. They are best stored in pairs with unlike poles on the same side, separated by wood, with pieces of soft iron placed across their ends.

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46. Q.196

    Why do the muscles that move a bone always work in pairs?

    1. A A muscle can only push, so another muscle is needed to pull the bone
    2. B One muscle supplies blood to the bone while the other one moves it
    3. C A muscle can only pull, so a second muscle must pull the bone back
    4. D Both muscles must contract at the same time to move the bone at all
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    Correct answer: (C) A muscle can only pull, so a second muscle must pull the bone back

    When a muscle contracts it becomes shorter and pulls the bone; it cannot push. To move the bone in the opposite direction, the other muscle of the pair contracts while the first one relaxes.

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47. Q.197

    The process of separating the seeds from the cotton fibres picked from cotton bolls is called:

    1. A Ginning
    2. B Spinning
    3. C Reeling
    4. D Knitting
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    Correct answer: (A) Ginning

    Separating the seeds from cotton is called ginning, done traditionally by hand and now also by machines. Spinning makes yarn from fibres, and reeling is taking out silk threads from cocoons.

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48. Q.198

    The upper part of our ear can be bent and folded easily, yet it keeps its shape. This part is supported by:

    1. A Cartilage
    2. B Bone
    3. C Muscle
    4. D Ligament
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    Correct answer: (A) Cartilage

    Cartilage is a part of the skeleton that is not as hard as bone and can be bent, which is why the upper ear can be folded. Bone is hard and cannot be bent.

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49. Q.199

    A Class 8 student says, 'Science is only about measuring things; imagination has no place in it.' Which response best reflects the nature of science?

    1. A Imagination is used only by those scientists who do not perform experiments
    2. B Imagination belongs only to art and literature and never to science
    3. C Science depends on measurement alone, so the student is right and imagination should be avoided
    4. D Imagination and creativity help scientists frame questions, hypotheses, models and explanations
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    Correct answer: (D) Imagination and creativity help scientists frame questions, hypotheses, models and explanations

    Scientific knowledge rests on evidence, but producing it also needs human imagination and creativity: inventing explanations, designing experiments and building models such as the particle model of matter. Calling science purely mechanical misrepresents how it works.

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50. Q.200

    Sleeping in a closed room with a coal fire (angithi) burning can be fatal. This is because:

    1. A Burning coal releases too much oxygen into the room
    2. B Incomplete burning of coal produces poisonous carbon monoxide
    3. C The coal fire turns the air of the room into acid rain
    4. D Burning coal gives out nitrogen, which makes the room humid
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    Correct answer: (B) Incomplete burning of coal produces poisonous carbon monoxide

    In a closed room there is not enough air, so the coal burns incompletely and produces carbon monoxide, a very poisonous gas that can kill people sleeping there.

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