CTET Science Paper 2 MCQs with Answers Set 08

Answer: (b) B will lose more heat than A

Explanation:
1. Both end at the freezer temperature below 0 °C.
2. Water B must first freeze, losing latent heat (50 g × 334 J/g ≈ 16700 J), which ice A does not lose, so B loses more.

Teacher's Note:
1. Latent heat of fusion is released during freezing.
2. Compare the extra step each substance has to go through.

Answer: (a) Scientific laws are descriptions of the relationships between observable phenomena.

Explanation:
1. A law describes a pattern or relationship in observed phenomena.
2. Theories explain; laws describe, and neither is higher than the other.

Teacher's Note:
1. Theories do not become laws.
2. Laws describe what happens; theories explain why.

Answer: (d) Helping students in talking, thinking, arguing and writing about science

Explanation:
1. Social constructivism (Vygotsky) says knowledge is built through social interaction and language.
2. Talking, arguing and writing about science is the most direct form of this.

Teacher's Note:
1. Language and dialogue are central tools of thought for Vygotsky.
2. Activities alone do not ensure meaning is built.

Answer: (c) Baking soda solution

Explanation:
1. Beetroot acts as an indicator and turns red/pink with a base.
2. Baking soda solution is basic; salt and glucose are neutral and lemon juice is acidic.

Teacher's Note:
1. Beetroot juice is red in acid and neutral and darker/purple-red in bases.
2. The key is kept as given.

Answer: (d) Wood, Air, Sand

Explanation:
1. Wood, air and sand are all mixtures of several substances.
2. Water and salt are pure substances, so options (a), (b) and (c) each contain one.

Teacher's Note:
1. Pure substance has fixed composition.
2. Water is a compound and salt (NaCl) is a compound.

Answer: (a) A is observation, B is inference

Explanation:
1. The blue black colour is seen directly, so A is an observation.
2. The presence of starch is concluded from that colour, so B is an inference.

Teacher's Note:
1. Observation uses the senses; inference is a conclusion.
2. Iodine turns blue black with starch.

Answer: (d) Object is at rest

Explanation:
1. A line parallel to the time axis means distance does not change with time.
2. That is an object at rest.

Teacher's Note:
1. Slope of a distance-time graph is speed.
2. Zero slope means zero speed.

Answer: (c) Both (A) and (B) are true.

Explanation:
1. At new moon the moon lies between earth and sun.
2. At full moon the earth lies between sun and moon (in line or nearly so). Both are true.

Teacher's Note:
1. Eclipses need exact alignment, which is why they do not occur every month.
2. Do not confuse the phases with eclipses.

Answer: (a) maximum

Explanation:
1. A parachute has a large surface area facing the air.
2. Larger area gives greater air resistance (drag), which slows the fall.

Teacher's Note:
1. Air drag increases with area and speed.
2. Streamlined shapes do the opposite.

Answer: (b) outermost, blue, complete

Explanation:
1. The outermost zone is the hottest, has enough oxygen and burns blue.
2. Combustion there is complete, so goldsmiths use it to melt gold.

Teacher's Note:
1. Innermost zone is dark and cold; middle is yellow and luminous.
2. Complete combustion gives the most heat.

Answer: (b) Z > X > Y > W

Explanation:
1. X displaces Y, so X > Y; X cannot displace Z, so Z > X.
2. Y displaces W, so Y > W. Together: Z > X > Y > W.

Teacher's Note:
1. A more reactive metal displaces a less reactive metal from its salt.
2. Build the chain from each pair.

Answer: (d) cell membrane, nucleus, mitochondria, cytoplasm

Explanation:
1. Animal cells have no cell wall and no plastids (chloroplasts).
2. Options (a), (b) and (c) each contain a cell wall or plastids, so they are plant-cell features.
3. Option (d) lists only parts found in an animal cell: membrane, nucleus, mitochondria and cytoplasm.

Teacher's Note:
1. Cell wall and plastids are the two quickest clues that separate plant cells from animal cells.
2. Scan each option for these two items first and eliminate.

Answer: (a) a, b, c

Explanation:
1. Science is tentative: knowledge can change with new evidence.
2. Scientific explanations must be falsifiable, i.e. open to being tested and disproved.
3. Science is also a process of describing and explaining the world, not a body of final or ultimate knowledge, so d is false.

Teacher's Note:
1. Words like 'ultimate' or 'final' about scientific knowledge signal a wrong statement.
2. Remember the nature of science as a process, tentative and testable.

Answer: (a) 101.4°C

Explanation:
1. Two big lines are 1 degree apart and have 5 divisions between them, so each division is 1 ÷ 5 = 0.2 degree.
2. Two more divisions add 2 × 0.2 = 0.4 degree.
3. Temperature = 101 + 0.4 = 101.4.

Teacher's Note:
1. Always find the least count first: value of one division = gap between big lines ÷ number of divisions.
2. A real clinical thermometer is marked in °F; the question's unit is kept as given.

Answer: (a) Observing, defining operationally

Explanation:
1. Students must look at the plants closely, which is observing.
2. They must state what features (for example green leaves, firm stem) make a plant 'healthy', which is defining operationally.
3. No prediction or measurement is asked for.

Teacher's Note:
1. Defining operationally means describing a term by what can be observed or done.
2. Match each skill to what students actually do in the task.

Answer: (a) A & B

Explanation:
1. Mountain trees such as conifers have sloping branches so that snow slides off.
2. Their leaves are needle-like to reduce water loss and let snow fall off.
3. Waxy thick stems and long penetrating roots are desert features.

Teacher's Note:
1. Pair habitats with adaptations: desert gives waxy stems and deep roots, mountains give conical shape, sloping branches and needle leaves.
2. This is a common matching mistake.

Answer: (a) Using systematic experimentation as a tool to discover/verify theoretical principles.

Explanation:
1. At the upper primary stage NCF 2005 stresses learning through familiar experience, hands-on activity and designing simple technological units.
2. Systematic experimentation to discover or verify theoretical principles is an objective of the secondary stage.

Teacher's Note:
1. NCF 2005 moves from experience and activity at the primary and upper primary stage to systematic experimentation at the secondary stage.
2. Watch for stage-specific words in such questions.

Answer: (b) Teacher ignoring students' erroneous responses

Explanation:
1. In a constructivist classroom learners build knowledge through discussion, planning and investigation.
2. The teacher listens to learners and uses their errors as a starting point for learning.
3. Ignoring erroneous responses wastes this information, so it is not constructivist.

Teacher's Note:
1. Learners' errors reveal their alternative conceptions and should be addressed, not ignored.
2. Constructivism is learner-centred and the teacher acts as a facilitator.

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

Explanation:
1. The moon's rotation period and revolution period are equal (about 27.3 days).
2. Because of this equal timing, the same side always faces the earth.
3. So A and R are both true and R explains A.

Teacher's Note:
1. This is called synchronous rotation or tidal locking.
2. The far side exists, but we never see it from the earth.

Answer: (b) Asking students to conduct water audit in neighbourhood

Explanation:
1. Sensitising learners works best through direct, real-life experience.
2. A water audit makes students measure and observe water use around them.
3. Slogans, posters and debates are mostly expressive and do not involve such first-hand experience.

Teacher's Note:
1. Hands-on, community-based activities build awareness and responsibility better than activities that only talk about a problem.
2. NCF 2005 encourages learning by doing.

Answer: (a) (A) is observation, (B) is inference.

Explanation:
1. (A) describes what was actually seen in one trial, so it is an observation.
2. (B) is a general conclusion drawn from such observations, so it is an inference.

Teacher's Note:
1. Observation is what we see or measure; inference is the conclusion we draw from it.
2. A general statement is usually an inference.

Answer: (a) Data and evidence are same

Explanation:
1. Data are raw observations or measurements; evidence is data that is interpreted to support or reject a claim.
2. So data and evidence are not the same.
3. The other three statements agree with accepted views of the nature of science.

Teacher's Note:
1. Science has no single fixed method.
2. Data become evidence only when they are used in an argument.

Answer: (a) Laws are generalisations whereas theories are explanations.

Explanation:
1. A law describes a pattern or generalisation in nature.
2. A theory explains why that pattern occurs.
3. The other options give irrelevant or wrong differences.

Teacher's Note:
1. A theory does not become a law with more evidence; they do different jobs.
2. Law describes what happens and theory explains why.

Answer: (c) (A) and (B) are true.

Explanation:
1. Parsimony means preferring the simplest adequate explanation, a recognised feature of science.
2. Science is also sceptical: claims are accepted only after evidence and are open to questioning.
3. Both statements are true.

Teacher's Note:
1. Features of science include being empirical, tentative, sceptical, parsimonious and self-correcting.
2. Remember the list as a set.

Answer: (b) allow self paced learning

Explanation:
1. An inclusive classroom respects the diverse needs and pace of every learner.
2. Self-paced learning lets each child progress at a suitable speed.
3. Favouring high achievers, a rigid standard curriculum or deleting tasks does not include all learners.

Teacher's Note:
1. Inclusion means adapting teaching to learners, not excluding or lowering expectations for some.
2. Flexible pace, varied tasks and multiple ways of learning support inclusion.

Answer: (c) Giving opportunity to handle various objects of different shape, size and material

Explanation:
1. Learners confuse density with heaviness because they only think of total weight.
2. Handling objects of different shape, size and material lets them compare small heavy-for-size objects with large light ones themselves.
3. This hands-on experience builds the idea better than telling, defining or a teacher demonstration.

Teacher's Note:
1. Learner-centred, hands-on experience is preferred in science teaching.
2. Density is mass per unit volume, so the objects' sizes must be compared as well.

Answer: (a) Both A and R are true and R is the correct explanation of assertion.

Explanation:
1. Ultrasound has frequency above 20,000 Hz.
2. Humans can hear only 20 Hz to 20,000 Hz, so ultrasound lies outside this range and cannot be heard.
3. So R is true and explains A.

Teacher's Note:
1. Infrasound is below 20 Hz and ultrasound is above 20,000 Hz; both are inaudible to humans.
2. Audible range is the key to such questions.

Answer: (c) A and C

Explanation:
1. Sound needs a material medium, so it cannot travel in vacuum (D) and D is left out.
2. Among the others the speed is lowest in a gas (air, about 340 m/s), higher in a liquid (water, about 1500 m/s) and highest in a solid (iron, about 5000 m/s).
3. So least is air (A) and maximum is iron (C).

Teacher's Note:
1. Speed of sound: solids > liquids > gases.
2. Sound does not travel through a vacuum at all.

Answer: (d) Only C

Explanation:
1. Asking all learners the same type of task ignores their diversity, and judging only by vocabulary ignores understanding.
2. Asking learners to justify their responses shows their reasoning, so it should be part of assessment.
3. Only (C) is correct.

Teacher's Note:
1. Good assessment checks reasoning and understanding, not just recall of terms.
2. Watch for 'only' in a statement, which usually makes it wrong.