CTET Science Paper 2 MCQs with Answers Set 10

Answer: (c) Make a protective solution that prevents rusting of iron.

Explanation:
1. An authentic task is a real-life task in which learners use what they learnt to solve a real problem.
2. Making a solution that prevents rusting of iron applies the idea of chemical change (rusting) to a real problem.
3. The other tasks only repeat classroom experiments.

Teacher's Note:
1. Authentic assessment asks learners to apply knowledge in realistic situations.
2. Repeating a standard experiment is not authentic.

Answer: (b) A-IV, B-V, C-III, D-II

Explanation:
1. Vitamin A deficiency causes loss of vision (night blindness) and Vitamin B (B1) deficiency causes beri-beri.
2. Vitamin C deficiency causes scurvy and iron deficiency causes anaemia.
3. So A-IV, B-V, C-III, D-II.

Teacher's Note:
1. Goitre is caused by iodine deficiency and rickets by vitamin D deficiency; both are extra items.
2. Learn the deficiency table together with the sources.

Answer: (d) Basing rural school curriculum on relatively simpler concepts.

Explanation:
1. Bridging the divide means giving rural learners equal quality and relevance, using their own context.
2. Giving rural schools a simpler curriculum lowers expectations and widens the gap.
3. The other three make science relevant and accessible to rural learners.

Teacher's Note:
1. Equity means the same high standards with locally relevant contexts, not a diluted curriculum.
2. NCF 2005 stresses linking science to the learner's environment.

Answer: (a) Only A

Explanation:
1. The observation only shows that the candle needs air, because once the air in the jar is used up it goes out.
2. It does not show which gas in the air is needed, so naming oxygen needs more evidence or knowledge beyond this observation.

Teacher's Note:
1. An inference must be supported by the observation itself.
2. Oxygen is the actual requirement, but this experiment alone does not show that.

Answer: (c) What would happen if there was no water cycle?

Explanation:
1. Divergent thinking means producing many different ideas for a problem or question.
2. 'What would happen if there was no water cycle?' has many possible answers.
3. The other questions have one correct answer or task.

Teacher's Note:
1. Divergent thinking questions are open-ended; convergent questions have one correct answer.
2. 'What if' questions are typical divergent items.

Answer: (a) Both (A) and (R) are true and (R) is correct explanation for (A)

Explanation:
1. Alternative conceptions do persist after instruction.
2. Scientific explanations often contradict everyday experience (for example heavier objects fall at the same rate), so learners keep their intuitive ideas.
3. So R explains A.

Teacher's Note:
1. Teaching needs to confront learners' ideas through conceptual change strategies.
2. Intuitive ideas make sense to learners in daily life.

Answer: (d) Both (A) and (B) are false

Explanation:
1. Data can be qualitative (colour, texture, observations) as well as numerical, so (A) is false.
2. There is no single scientific method, so (B) is false.

Teacher's Note:
1. Both qualitative and quantitative data are valid in science.
2. Words like 'always' and 'only' signal false statements.

Answer: (a) S1 is fact and S2 is inference

Explanation:
1. S1 can be directly observed under a microscope or by testing, so it is a fact.
2. S2 is a conclusion drawn from experiments on photosynthesis, so it is an inference.

Teacher's Note:
1. Facts are directly observed; inferences are drawn from evidence.
2. This item follows the source key.

Answer: (c) (A) is observation and (B) is inference

Explanation:
1. (A) is what the student saw, so it is an observation.
2. (B) is a conclusion drawn from the blue-black colour, so it is an inference.

Teacher's Note:
1. Observation is what we see; inference is what we conclude from it.
2. Blue-black colour with iodine is the test for starch.

Answer: (d) Accept the response and explain the logic

Explanation:
1. The learner is reasoning from a real observation, even though the conclusion is wrong.
2. A good teacher accepts the effort and then guides the learner to see why drain water is not pure water, building on the learner's idea.

Teacher's Note:
1. Do not dismiss or ridicule children's ideas; use them as the starting point.
2. Telling the answer directly does not change the child's thinking.

Answer: (a) Asking students to define the concept

Explanation:
1. Defining a concept can be done by memorising words without understanding.
2. Generalising from examples, giving non-examples and explaining in their own words need real understanding, so they are preferred.

Teacher's Note:
1. Concept understanding is shown by using examples, non-examples and own words.
2. Rote definitions are the weakest evidence of understanding.

Answer: (d) Infinite

Explanation:
1. With two parallel mirrors, each image acts as an object for the other mirror.
2. This repeats again and again, so the number of images is infinite (in practice limited only by dimming and alignment).
3. The number of images is given by 360° ÷ θ − 1, which tends to infinity as θ tends to 0°.

Teacher's Note:
1. For two mirrors at angle θ, n = 360°/θ − 1, and parallel mirrors mean θ = 0°.
2. Repeated reflections are seen in barber shops.

Answer: (b) Only B

Explanation:
1. Cloning is also possible in plants (for example tissue culture), so A is false.
2. Cloning does not always produce many offspring (Dolly was a single clone), so C is false.
3. Cloning always gives an exact genetic copy of a cell, part or organism, so only B is always true.

Teacher's Note:
1. A clone is genetically identical to the parent.
2. 'Always' and 'only' in a statement should be tested with a counter-example.

Answer: (c) Students must be required to memorize facts and reproduce when needed.

Explanation:
1. The essence of science lies in inquiry, multiple methods, its nature and its history.
2. Memorising and reproducing facts does not develop an understanding of science as a process, so it is the exception.

Teacher's Note:
1. Rote memorisation goes against NCF 2005.
2. Science education should emphasise the process of science.

Answer: (b) C, D

Explanation:
1. Continuous assessment is part of teaching-learning and improves it, so A is false.
2. Recording every task is not necessary, which also makes B a wrong statement of good practice.
3. Qualitative criteria (C) give meaningful feedback, and assessment can sample key concepts, so (D) is correct; C and D are correct.

Teacher's Note:
1. Assessment should be meaningful and manageable, not exhaustive.
2. Sampling concepts and using qualitative criteria are accepted practices.

Answer: (c) Low pressure system with high speed winds revolving around it

Explanation:
1. A cyclone forms around a low-pressure centre, with air rushing in and spiralling upwards.
2. Cyclones have strong, high-speed winds revolving around the centre.

Teacher's Note:
1. Cyclones have low pressure and high winds; anticyclones have high pressure.
2. The eye of a cyclone is calm.

Answer: (c) Mercury < Aluminium < Copper < Iron

Explanation:
1. Melting points: mercury −39 °C, aluminium about 660 °C, copper about 1085 °C and iron about 1538 °C.
2. So the increasing order is mercury < aluminium < copper < iron.

Teacher's Note:
1. Mercury is liquid at room temperature, so it has the lowest melting point.
2. Remember rough values for common metals.

Answer: (a) Include typical as well as non-typical examples when introducing a concept

Explanation:
1. Students over-generalise because they have seen only typical metals.
2. Including non-typical examples (for example mercury is a liquid and sodium is soft) breaks the over-generalisation.

Teacher's Note:
1. Counter-examples help correct over-generalised ideas.
2. Show both typical and exceptional cases when teaching a concept.

Answer: (a) Sink

Explanation:
1. Density of the ball = mass ÷ volume = 30 g ÷ 25 cm³ = 1.2 g/cm³.
2. Water has density 1 g/cm³, and 1.2 > 1, so the ball sinks.

Teacher's Note:
1. An object sinks if its density is greater than the liquid's.
2. Compare densities, not masses.

Answer: (a) High resistance and high melting point

Explanation:
1. High resistance makes the filament get very hot when current passes (heating effect).
2. A high melting point lets it get white hot without melting, so it glows.

Teacher's Note:
1. Tungsten is used because of its high melting point.
2. The heating effect is H = I²Rt, so high R means more heat.

Answer: (a) Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion

Explanation:
1. Atmospheric pressure falls with altitude.
2. A liquid boils when its vapour pressure equals the outside pressure, so lower pressure means a lower boiling point.
3. So both are true and R explains A.

Teacher's Note:
1. This is why cooking takes longer on mountains.
2. A pressure cooker raises pressure and the boiling point.

Answer: (c) Virtual image cannot be projected on screen while real image can be projected on a screen.

Explanation:
1. A real image is formed where light rays actually meet, so it can be caught on a screen.
2. A virtual image is formed where rays only appear to meet, so it cannot be projected on a screen.

Teacher's Note:
1. Real images are inverted and virtual images are erect in the common cases, but the screen test is the defining difference.
2. Plane mirrors always form virtual images.

Answer: (b) A-Gravitational force, B-Pressure, C-Magnetic force

Explanation:
1. Gravitational force acts between every pair of objects.
2. Force per unit area is pressure.
3. A non-contact force acts without touching; magnetic force is one, but friction is a contact force.

Teacher's Note:
1. Non-contact forces: gravitational, magnetic and electrostatic.
2. Friction and muscular force need contact.

Answer: (d) Only (D)

Explanation:
1. A more reactive metal displaces a less reactive metal from its compound.
2. Na is above Mg, Mg is above Cu and Zn is above Cu, so (A), (B) and (C) are feasible.
3. Cu is below Fe, so Cu cannot displace Fe from FeSO₄; only (D) is not feasible.

Teacher's Note:
1. Reactivity order: Na > Mg > Zn > Fe > Cu.
2. Check the position of the free metal against the metal in the compound.

Answer: (d) Carbon monoxide and Carbon dioxide

Explanation:
1. Carbon forms CO and CO₂, both colourless and odourless gases.
2. CO is toxic because it binds to haemoglobin, and CO₂ is a greenhouse gas.
3. Sulphur oxides have a pungent smell, and water and hydrogen peroxide are liquids.

Teacher's Note:
1. In option (a) the order is reversed, because N₂O is the greenhouse gas and NO the toxic one.
2. Check the order of A and B.

Answer: (a) Pitcher plant

Explanation:
1. The pitcher plant has chlorophyll and makes its own food, so it is an autotroph, and it also digests insects, so it is a heterotroph.
2. Algae are autotrophs only, Cuscuta is a parasite, and fungi are not plants.

Teacher's Note:
1. Insectivorous plants get nitrogen from insects.
2. Cuscuta is a partial parasite but has no chlorophyll.

Answer: (c) A-(iii), B-(v), C-(i), D-(ii), E-(iv)

Explanation:
1. Malleable metals can be beaten into thin foils, so A matches wrapping food (iii).
2. A high melting point suits heating elements (v); a good conductor suits electrodes (i); strength suits bridges (ii).
3. High thermal expansion makes mercury useful in thermometers (iv). This gives option (c).

Teacher's Note:
1. Match each use with the property that makes it possible.
2. A quick way is to fix the surest pairs (A-iii, E-iv) and eliminate options.

Answer: (c) C and D

Explanation:
1. Atoms are neither created nor destroyed in a reaction, so the number of atoms of each kind and the total mass stay the same (law of conservation of mass).
2. Physical states and the number of molecules can change, e.g. 2H₂ + O₂ → 2H₂O (3 molecules become 2).

Teacher's Note:
1. Atoms are conserved, molecules are not.
2. Do not confuse the number of molecules with the number of atoms.

Answer: (b) Timbre

Explanation:
1. Pitch depends on frequency and loudness on amplitude.
2. Timbre (quality) depends on the waveform and overtones, so it separates two sounds of equal pitch and loudness.

Teacher's Note:
1. Timbre lets us tell a violin from a flute playing the same note.
2. Shrillness is just another word for pitch.