CTET Science Paper 2 MCQs with Answers Set 09

Answer: (d) (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)

Explanation:
1. Algae reproduce by fragmentation and fungi by spores.
2. Dahlia reproduces from its (tuberous) roots.
3. Cactus reproduces when a part of the body breaks off and grows into a new plant, so the matching is (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii).

Teacher's Note:
1. Asexual methods: fragmentation, spore formation, budding, vegetative propagation.
2. Link each example from the textbook with its method.

Answer: (b) (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Explanation:
1. Flax fibre is obtained from the stem, silk from the cocoon of the silkworm and coconut fibre from the husk.
2. Cotton is the remaining pair; of the given parts it is matched with the flower (cotton fibre grows on the seed of the cotton flower's fruit).
3. So (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i).

Teacher's Note:
1. Use the sure matches first and eliminate.
2. Botanically cotton fibre comes from the seed coat in the boll, but 'flower' is the nearest listed part.

Answer: (a) To provide shape and rigidity to the cells

Explanation:
1. The nucleus controls cell activities, carries genes that pass traits to offspring, and its pores let materials move between nucleus and cytoplasm.
2. Giving shape and rigidity is done by the cell wall in plants and the cytoskeleton, not by the nucleus.

Teacher's Note:
1. The nucleus is called the control centre of the cell.
2. Shape and rigidity belong to the cell wall or cytoskeleton.

Answer: (c) Iron can displace copper from copper sulphate solution but cannot displace aluminium from aluminium sulphate solution.

Explanation:
1. Reactivity order: Al > Zn > Fe > Cu, so (a) and (b) are false.
2. Iron is above copper, so it displaces copper from copper sulphate; it is below aluminium, so it cannot displace aluminium.
3. Aluminium is above iron and does displace iron, so (d) is false; (c) is correct.

Teacher's Note:
1. A more reactive metal displaces a less reactive metal from its salt solution.
2. Learn the activity series: K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Ag, Au.

Answer: (b) Liver, bile juice, fats

Explanation:
1. The liver is the largest gland in the human body.
2. It secretes bile juice, which breaks up (emulsifies) fats for digestion.
3. So A = liver, B = bile juice, C = fats.

Teacher's Note:
1. Insulin is a hormone and does not digest food.
2. Bile contains no enzymes but helps fat digestion.

Answer: (b) Calcium, Calcium hydroxide, red, blue, Carbon dioxide

Explanation:
1. Calcium reacts with oxygen and water to give calcium hydroxide, a base.
2. A base turns red litmus blue.
3. Its solution (lime water) turns milky when carbon dioxide is passed, because calcium carbonate forms.

Teacher's Note:
1. Lime water turning milky is the standard test for carbon dioxide.
2. Bases turn red litmus blue; acids turn blue litmus red.

Answer: (b) Litmus, turmeric

Explanation:
1. Litmus (from lichens) and turmeric come from natural sources.
2. Phenolphthalein and methyl orange are synthetic indicators.
3. So only option (b) has two natural indicators.

Teacher's Note:
1. China rose, red cabbage and turmeric are natural indicators.
2. Phenolphthalein and methyl orange are synthetic.

Answer: (a) (C) and (D)

Explanation:
1. Desert plants have deep roots to reach water and fleshy stems to store it.
2. Their leaves are reduced to spines, with the waxy coating on the stem, so (C) is not characteristic.
3. Sloping branches are a feature of mountain trees, so (D) is not a desert feature.

Teacher's Note:
1. Desert: spines for leaves, thick waxy stem, deep roots.
2. Mountain: conical shape and sloping branches.

Answer: (a) Identical, one, one

Explanation:
1. Identical twins form when one egg is fertilised by one sperm and the zygote later splits into two embryos.
2. Fraternal twins form when two eggs are fertilised by two different sperms.
3. So X = identical, Y = one, Z = one.

Teacher's Note:
1. Identical twins have the same genetic material and are of the same sex.
2. Fraternal twins develop from two separate zygotes.

Answer: (b) Bag with wide strap as force per unit area is less

Explanation:
1. Pressure = force ÷ area, and the force (weight of the books) is the same for both bags.
2. A wide strap has a larger area, so pressure on the shoulder is less and it is more comfortable.
3. So choose the wide strap, because force per unit area is less.

Teacher's Note:
1. For the same force, larger area gives smaller pressure.
2. This is the same idea as sharp knives (small area, high pressure).

Answer: (c) The tea in the metal cup does not remain hot for longer time as metal is good conductor of heat

Explanation:
1. Metal is a good conductor, so heat passes quickly from the tea through the cup to the surroundings.
2. Plastic is a poor conductor, so it loses heat slowly.
3. Tea in the metal cup cools faster, as stated in (c).

Teacher's Note:
1. Good conductors of heat make things cool (and warm) quickly.
2. The other options give wrong conclusions from correct ideas.

Answer: (c) It is highly malleable.

Explanation:
1. Foil is a very thin sheet, which is possible only because aluminium is highly malleable and can be beaten or rolled into thin sheets.
2. Aluminium does react with oxygen (it forms a thin protective oxide layer), so (b) is not correct.

Teacher's Note:
1. Malleability is the property of being beaten into sheets.
2. Aluminium is protected by its oxide layer, not because it fails to react.

Answer: (b) the sperm had one Y chromosome

Explanation:
1. Every egg carries an X chromosome, so the sex of the child depends on the sperm.
2. A sperm with a Y chromosome gives XY, a male; a sperm with X gives XX, a female.

Teacher's Note:
1. Females are XX and males are XY.
2. Eggs never carry Y.

Answer: (d) Resistance will remain unchanged

Explanation:
1. Resistance R = ρL ÷ A.
2. With length 2L and area 2A: R' = ρ(2L) ÷ (2A) = ρL ÷ A = R.
3. So the resistance is unchanged.

Teacher's Note:
1. Resistance is directly proportional to length and inversely proportional to area.
2. The factor 2 on top and bottom cancels.

Answer: (b) A, B, D

Explanation:
1. An object sinks in a liquid if its density is greater than that of the liquid, so density of X > density of P (A is true).
2. It floats in R, so density of X < density of R (B is true).
3. Then density of P < density of X < density of R, so D is true and C is false.

Teacher's Note:
1. Sinks means the object is denser than the liquid; floats means it is less dense.
2. Combine the inequalities to compare the liquids.

Answer: (d) A and B may be elements or compounds, C is a compound

Explanation:
1. In a combination reaction two or more substances join to form a single new substance.
2. The reactants may be elements or compounds, but the product formed by combination is always a compound.
3. A mixture is not a reaction product.

Teacher's Note:
1. Two elements cannot give an element in a combination reaction.
2. Reaction products are pure substances, not mixtures.

Answer: (c) It is not an effective approach for encouraging inquiry.

Explanation:
1. The teacher gives the definitions first and then shows what to expect, so students only verify what they were told.
2. Inquiry-oriented teaching lets learners explore, predict, test and reach the concept themselves.
3. So the approach does not encourage inquiry.

Teacher's Note:
1. Inquiry starts from questions and exploration, and the definition comes last.
2. More examples or end questions do not change the order of teaching.

Answer: (b) (A)-(iii), (B)-(iv), (C)-(i), (D)-(ii)

Explanation:
1. Finding differences between seeds is observing; giving a possible reason for faster growth is hypothesising.
2. Drawing a diagram of changes is communication.
3. Saying what will happen if the water is doubled is predicting.

Teacher's Note:
1. Hypothesis explains why; prediction says what will happen.
2. Match each question to the verb in it (compare, explain, draw, foretell).

Answer: (c) (A) is true but (R) is false

Explanation:
1. An electromagnet acts as a magnet only while current flows, so it is temporary and A is true.
2. It can be made very strong by increasing the number of turns, current and using a soft iron core, so R is false.

Teacher's Note:
1. Temporary means the magnetism disappears when the current is switched off.
2. Electromagnets are used in cranes to lift heavy loads, so they are not weak.

Answer: (b) 'A' could be convex mirror or concave lens

Explanation:
1. A convex mirror and a concave lens always form virtual, erect and diminished images, so 'A' could be either of them.
2. Real and inverted images are mostly formed by a concave mirror and a convex lens, so 'B' could be those.
3. Only option (b) is correct.

Teacher's Note:
1. Convex mirror and concave lens: always virtual and erect. Concave mirror and convex lens: real or virtual depending on object distance.
2. A convex lens and a concave mirror can also form virtual images when the object is very close.

Answer: (c) It may be uniform or the object is at rest

Explanation:
1. A straight line sloping upward on a distance-time graph means equal distances in equal times, i.e. uniform motion.
2. A straight line parallel to the time axis means distance does not change, i.e. the object is at rest.
3. Without knowing which, we can only say it may be uniform motion or rest.

Teacher's Note:
1. The slope of a distance-time graph gives speed.
2. A curved line means non-uniform motion.

Answer: (a) 60°

Explanation:
1. The angle of incidence is 30°, and by the law of reflection the angle of reflection is also 30°.
2. The incident and reflected rays lie on opposite sides of the normal, so the angle between them is 30° + 30° = 60°.

Teacher's Note:
1. Angles of incidence and reflection are measured from the normal.
2. A common mistake is to answer 30°, which is only one of the two angles.

Answer: (c) Rolling friction is less than sliding friction

Explanation:
1. Rolling needs less force than sliding, so rolling friction is less than sliding friction.
2. Friction depends on the normal force, which depends on mass, so (a) is false.
3. A parked car on a slope has static friction, and air resistance opposes the motion, so (b) and (d) are false.

Teacher's Note:
1. This is why wheels and ball bearings reduce friction.
2. Static friction exists even when there is no motion.

Answer: (c) (A) is true but (R) is false

Explanation:
1. The outermost zone is the hottest part of a flame because of complete combustion, which is why goldsmiths use it, so A is true.
2. R says the zone is not too hot, which is false.

Teacher's Note:
1. Flame zones: the innermost is the coolest, the middle is luminous and the outermost is the hottest.
2. The key follows the source.

Answer: (b) Vitamin C, Iron

Explanation:
1. Vitamin C helps the body absorb iron from food.
2. Calcium absorption needs vitamin D, not A or B, so options with calcium are wrong.

Teacher's Note:
1. Vitamin D is needed for calcium and vitamin C for iron absorption.
2. Citrus fruits eaten with iron-rich food improve iron absorption.

Answer: (a) Plants having tap root have reticulate venation.

Explanation:
1. Carrot has a tap root.
2. Plants with tap roots (dicots) generally have leaves with reticulate venation, which supports the assertion.

Teacher's Note:
1. Tap root goes with reticulate venation and fibrous root goes with parallel venation.
2. These are general rules based on dicots and monocots.

Answer: (a) Wheat, Mustard

Explanation:
1. Rabi crops are sown in winter (October-November) and harvested in spring (March-April).
2. Wheat and mustard are both Rabi crops, while paddy and maize are Kharif crops.

Teacher's Note:
1. Kharif crops: paddy, maize, cotton, soybean. Rabi crops: wheat, gram, peas, mustard, linseed.
2. Peas are Rabi too, but the other crop in (c) and (d) is Kharif.

Answer: (d) A pair of balanced forces is acting on it.

Explanation:
1. The weight of the book acts downwards and the normal force from the table acts upwards.
2. These are equal and opposite, so they are balanced and the net force is zero.

Teacher's Note:
1. Balanced forces do not change the state of rest.
2. No net force does not mean that no force acts.

Answer: (a) None

Explanation:
1. Bring the labelled pole near a pole of another magnet: attraction means the opposite pole, and repulsion means the same pole.
2. In this way every pole of every magnet can be identified using the one labelled pole, so no more labelled poles are needed.

Teacher's Note:
1. Like poles repel and unlike poles attract, so repulsion is the sure test for a magnet's pole.
2. Once one magnet's poles are known, it can label the rest.