Mathematics and Science PYQs

The correct answer is S1 is true and S2 is false

Concept:

• Self-pollination involves the transfer of pollen from the anther to the stigma of the same flower or another flower on the same plant. It occurs in bisexual (hermaphroditic) flowers, which contain both male (stamens) and female (pistils) reproductive organs.
• Cross-pollination involves the transfer of pollen from the anther of one flower to the stigma of another flower on a different plant. Cross-pollination generally occurs in unisexual flowers (where male and female reproductive organs are in separate flowers) but can also occur in bisexual flowers under certain conditions.

Explanation:

• S1 is true: Self-pollination can only take place in bisexual flowers because these flowers have both male and female reproductive organs, allowing them to transfer pollen within the same flower or between flowers on the same plant.
• S2 is false: Cross-pollination is not limited to unisexual flowers. While it is common in unisexual flowers, it can also occur in bisexual flowers, where pollen is transferred from one plant to another by wind, insects, or other pollinators.

Children come into the classroom with their own pre-existing ideas about how the world works. These ideas, often referred to as alternative conceptions or preconceptions, may differ significantly from scientifically accepted concepts. 

Key Points

• Children’s ideas are usually stable because they are deeply rooted in everyday experiences and observations. These ideas are often formed through direct interaction with observable phenomena, such as watching objects fall or seeing the sun move across the sky.
• Also, research shows that children’s conceptions often follow similar developmental patterns across cultures, as they build understanding through similar stages.
• Furthermore, these ideas are typically domain-specific, meaning a child might hold scientifically accurate views in one area (like plants) but not in another (like electricity).
• However, these ideas are not easy to modify. Since they are intuitive and often feel “correct” to the child, it takes careful teaching, questioning, and conceptual conflict to shift them toward scientific understanding.

Hence, the correct answer is (A), (B), (C), (E).

The correct answer is Soil with low water holding capacity has good aeration and high percolation rate.

Explanation:

• Soil water holding capacity refers to the soil's ability to retain water for use by plants. It is influenced by the soil's texture, structure, organic matter content, and depth.
• Aeration in soil refers to the exchange of air within the soil with the atmosphere. Good aeration ensures that roots get enough oxygen to support respiration and growth.
• Percolation rate is the rate at which water moves through soil pores. High percolation rates mean that water drains quickly through the soil, while low percolation rates indicate slower drainage.
• Soils with low water holding capacity, such as sandy soils, typically have large pore spaces, which allows for good aeration and a high percolation rate.

Other Options:

• Option 1: Soil with low water holding capacity has poor aeration and high percolation rate. This is incorrect because soil with low water holding capacity typically has good aeration. Poor aeration is associated with soils that have high water holding capacity, like clay.
• Option 2: Soil with low water holding capacity has good aeration and low percolation rate. This is incorrect because soil with low water holding capacity generally has a high percolation rate, not a low one.
• Option 3: Soil with low water holding capacity has poor aeration and low percolation rate. This is incorrect because soil with low water holding capacity generally has good aeration and high percolation rate. Poor aeration and low percolation rate are characteristics of soils with high water holding capacity.

CONCEPT:

Properties of Compounds

• Δ compound is a substance made up of two or more elements that are chemically bonded in a fixed ratio.
• Compounds have unique properties that are different from those of their constituent elements.
• The composition of a compound is always fixed, and compounds cannot be separated into their elements by physical methods; they can only be separated through chemical reactions.

EXPLΔNΔTION:

• Statement Δ: Compounds show the properties of constituent substances.
• This is false. Compounds have different properties from their constituent elements. For example, water H₂O has properties completely different from those of hydrogen H₂ and oxygen O₂, even though they are the constituents of water.
• Statement B: Only elements can react to form compounds.
• This is false. Compounds are formed when atoms of different elements react chemically. It is not only individual elements that react to form compounds e.g., H₂ and O₂ molecules can combine to form water.
• Statement C: The composition of each compound is always fixed.
• This is true. Compounds have a fixed ratio of elements, and their composition remains constant. For example, water always consists of two hydrogen atoms and one oxygen atom H₂O.
• Statement D: Compounds can be separated by physical and chemical methods.
• This is false. Compounds can only be separated by chemical methods e.g., electrolysis or other chemical reactions, not by physical methods, as physical methods are used only to separate mixtures.

Therefore, the correct answer is 3 Δ, B, D.

The correct answer is: Option 3) Refractive index of A and C are less than B

Explanation:

When a ray of light passes from one medium to another, its speed changes according to the refractive index of the media. The refractive index (n) is given by:

n = c / v, where:

c is the speed of light in a vacuum

v is the speed of light in the medium

From the question, we know that the speed of light decreases when it enters medium B from medium A, and it increases when entering medium C from medium B.

If the speed decreases when entering medium B, it means the refractive index of B is greater than that of A because a higher refractive index corresponds to a lower speed of light in the medium.

If the speed increases when entering medium C, it means the refractive index of C is less than that of B, because a lower refractive index corresponds to a higher speed of light in the medium.

The correct answer is Thyroxine, Thyroid, Iodine

Explanation:

• The thyroid gland is a vital hormone gland that plays a major role in the metabolism, growth, and development of the human body. It helps to regulate many body functions by releasing a steady amount of thyroid hormones into the bloodstream.
• Thyroxine (T4) is one of the hormones produced by the thyroid gland. It is responsible for regulating metabolism, heart and digestive functions, muscle control, brain development, and bone maintenance.
• Iodine is an essential nutrient that is crucial for the production of thyroxine. A deficiency in iodine can lead to thyroid gland problems, including goiter and hypothyroidism.

Other Options:

• Insulin, Pancreas, Sugar: Insulin is a hormone produced by the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into tissues. While sugar intake can affect insulin levels, this option does not match the regulation of carbohydrate, protein, and fat metabolism.
• Adrenaline, Adrenal, Salts: Adrenaline is a hormone produced by the adrenal glands that prepares the body for 'fight or flight' responses by increasing heart rate, blood flow, and energy availability.
• Growth hormone, Pituitary, Proteins: Growth hormone is produced by the pituitary gland and is important for growth, body composition, cell repair, and metabolism

In science teaching, process skills refer to the abilities that students use to investigate scientific phenomena. These skills help learners think and act like scientists by engaging them in meaningful, hands-on learning.

Key Points

• In the given activity, students are tasked with identifying two bar magnets from four iron bars.
• This involves multiple cognitive and procedural actions.
• First, students need observation skills to carefully notice interactions like attraction or repulsion between bars. They will also apply classification skills to group the bars based on their magnetic behavior.
• Finally, students use inferring skills by drawing conclusions based on their observations, for instance, if a bar repels another, it must be a magnet.
• While skills like measuring or controlling variables are important in other contexts, they are not central to this specific activity, which does not involve numerical measurement or altering conditions systematically.

Hence, the correct answer is Observation, Classification, Inferring.

The correct answer is: Option 3) B and C

Explanation:

We are given information about the substances' states and whether they vaporize on burning:

Substance A: Solid, does not vaporize on burning.

Substance B: Liquid, vaporizes on burning.

Substance C: Solid, vaporizes on burning.

Substance D: Liquid, does not vaporize on burning.

When a substance vaporizes on burning, it tends to give a flame due to the vaporized particles combusting. So, substances that vaporize on burning are more likely to give a flame.

Substance A does not vaporize on burning, so it will not give a flame.

Substance D also does not vaporize on burning, so it will not give a flame either.

Substance B and C vaporize on burning, so they are likely to give a flame.

The correct answer is: Option 3) (A) is true and only (R2) is correct explanation for (A).

Explanation:

Assertion (A): Convex mirrors are used as rearview mirrors in vehicles.

This is true. Convex mirrors are widely used as rearview mirrors in vehicles because they provide a wider field of view and reduce the blind spots, helping the driver to see more area behind the vehicle.

Reason (R1): Convex mirrors form erect and enlarged images.

This is incorrect. Convex mirrors always form diminished, virtual, and upright images, not enlarged images. They help in reducing the image size to show a wider area, but they do not enlarge the image.

Reason (R2): Convex mirrors have a wider field of view.

This is correct. Convex mirrors have a wider field of view because they diverge light rays, allowing for a larger area to be reflected, making them ideal for use in rearview mirrors.

Concept and Answer:

We are given three media A, B and C such that their densities satisfy

ρ_B < ρ_A < ρ_C.

The speed of sound in a medium is

v = √(E / ρ)

where E is the modulus of elasticity (rigidity) and ρ is the density of the medium.

In general, solids are much more rigid than liquids and gases. As we move from a less dense medium (like gas) to a more dense and much more rigid medium (like a solid), the sharp increase in elasticity dominates over the effect of higher density, so the speed of sound becomes larger.

Thus, among the three media, medium C is taken to be the most rigid and hence provides the largest ratio E / ρ.

⇒ v_C > v_A > v_B

Therefore, sound travels fastest in medium C.

In education, particularly in STEM (Science, Technology, Engineering, and Mathematics), various studies and observations have shown that achievement can sometimes be influenced by gender. 

 Key Points

• The assertion claims that achievement in STEM is influenced by gender. This is not universally true; gender itself is not a determinant of STEM performance.
• The reason says problem-solving strategies differ between boys and girls. While some differences in approach may exist, they are not consistent enough to be a general fact, and they do not imply a difference in achievement.

 

 

Hence**, Both (A) and (R) are false.**

The correct answer is a - iii, b - i, c - iv, d - ii

Explanation:

• Aquatic plants have developed various adaptations to survive and thrive in water environments. These adaptations help them to float, resist water currents, and avoid decay, among other functions.
• Adaptations such as large circular leaves, waxy coatings, stems with large tunnels and holes, and ribbon-like leaves are common among aquatic plants.
• Large circular leaves (a - iii): These leaves help in providing buoyancy, allowing the plant to float on the water surface and access sunlight for photosynthesis.
• Waxy coating (b - i): The waxy coating is helpful in protecting against decay by preventing water from saturating the leaves and stems, which can lead to rot and fungal infections.
• Stems have large tunnels and holes (c - iv): These structures help the plant stay afloat by trapping air and reducing the overall density of the stems, enabling them to float on or near the water surface.
• Ribbon-like leaves (d - ii): These leaves offer resistance to water currents by being flexible and narrow, allowing the plant to sway with the flow rather than being uprooted or damaged.

CONCEPT:

Reactivity Series of Metals

• The reactivity series of metals is a list of metals arranged in order of their reactivity. The more reactive a metal, the easier it loses electrons to form positive ions.
• Generally, metals like sodium, potassium, and calcium are highly reactive and readily react with water, while metals like gold, platinum, and silver are much less reactive.
• Reactivity also influences how metals interact with other substances, such as acids and oxygen.

EXPLANATION:

• Statement (A): Zinc is more reactive than iron but less reactive than aluminium.
• This is true. In the reactivity series, Aluminum is more reactive than Zinc, and Zinc is more reactive than Iron. So, this statement is correct.
• Statement (B): Sodium is more reactive than potassium and calcium.
• This is false. In the reactivity series, Potassium is more reactive than Sodium, and Calcium is more reactive than both. Therefore, this statement is incorrect.
• Statement (C): Aluminium is more reactive than magnesium.
• This is false. Magnesium is more reactive than Aluminium in the reactivity series. Therefore, this statement is incorrect.

Therefore, the correct answer is Only (A).

The correct answer is Layering, Jasmine

Explanation:

• Vegetative Propagation is a type of asexual reproduction in plants where new plants grow from parts of the parent plant, such as stems, roots, or leaves. This allows plants to reproduce without the need for seeds.
• Layering technique involves bending a branch or stem of a plant and burying it in the soil while it is still attached to the parent plant. Over time, the buried part develops roots and can be separated from the parent plant to grow independently. This method is commonly used for plants that have difficulty rooting from cuttings.
• Jasmine is a common example of a plant that can be propagated through layering. The branches of jasmine plants are flexible and can easily be bent and buried in the soil to encourage root development.

Other Options:

• Cutting, Potato: Cutting is a method where a part of the plant, usually a stem or leaf, is cut and planted in soil or water to grow a new plant. Potatoes are grown through tuber propagation, not cutting.
• Grafting, Rose: Grafting involves joining two plants together so that they grow as one. A stem from one plant (the scion) is attached to the root system of another plant (the rootstock). Roses are commonly propagated through grafting, but this is different from layering.
• Budding, Hydra: Budding is a form of asexual reproduction in which a new organism develops from an outgrowth or bud on the parent. Hydra is an animal, not a plant.

The correct answer is (A) is true and (R) is false.

Concept:

• The circulatory system consists of arteries and veins that transport blood throughout the body.
• Arteries carry oxygenated blood away from the heart to the tissues, while veins carry deoxygenated blood back to the heart.
• Arteries have thick and elastic walls to withstand and regulate the high pressure of blood pumped by the heart. This elasticity helps in maintaining a continuous flow of blood even when the heart is in between beats.
• Veins have thinner walls compared to arteries and contain valves to prevent backflow of blood, as the pressure in veins is lower and blood is often moving against gravity.

Explanation:

• Assertion (A): "Arteries have thick and elastic walls as compared to veins." This statement is true because arteries need to handle the high pressure of blood coming directly from the heart.
• Reason (R): "The pressure of blood flow in arteries is low as compared to veins." This statement is false because the pressure in arteries is high due to the direct force exerted by the heart's contractions.

The correct answer is Both (A) and (B) are true

Explanation:

• Bile juice is a digestive fluid produced by the liver and stored in the gallbladder. It is released into the small intestine to aid in the digestion of fats and neutralize stomach acid.

(A) It makes the partly digested food coming from the stomach alkaline:

• The chyme (partly digested food) coming from the stomach is highly acidic due to gastric acids.
• Bile contains bicarbonate ions which help to neutralize this acid, making the chyme alkaline as it enters the small intestine.
• This alkaline environment is necessary for the proper functioning of digestive enzymes in the small intestine.

(B) It helps in the digestion of fats:

• Bile contains bile salts which are crucial for the digestion and absorption of fats.
• Bile salts emulsify large fat globules into smaller droplets, increasing the surface area for the action of the enzyme lipase.
• This emulsification process is essential for the efficient breakdown and absorption of dietary fats.

Understanding the nature of science is essential for teaching and learning science meaningfully. It involves recognizing how scientific knowledge is generated, validated, and influenced.

Key Points

• Statement (A): Scientific ideas are not affected by cultural context. This is false. Scientific development is often influenced by cultural, social, and historical contexts. For instance, the priorities of a society, its available technology, and its values can shape the kind of questions scientists ask and the direction of research.
• Statement (B): There is no single scientific method. This is true. Science does not follow a rigid, step-by-step method. Instead, it includes a variety of practices such as observation, experimentation, modeling, hypothesis testing, and argumentation. Scientists may use different approaches depending on the question or context.

Hence, the correct answer is (A) is false and (B) is true.

Art Integrated Learning (AIL) is an approach that uses art forms such as visual arts, music, dance, theatre, etc as a medium to teach and reinforce concepts in various subjects like Science. It promotes experiential learning, creativity, critical thinking, and expression.

Key Points

• Projects allow students to explore scientific ideas creatively, for example, creating models, dioramas, posters, or dramatizations to explain scientific concepts like ecosystems, the solar system, or human anatomy.
• Portfolios provide a space for students to collect and reflect on their art-based science work, encouraging personal expression and showcasing learning journeys through drawings, concept maps, and creative presentations.

Hint

• Anecdotal records and Journal writing are more focused on recording observations or reflective writing, which are useful for assessment and personal tracking but offer limited integration with art forms.
• Field trips can support learning through experience, and journal writing can complement them, but they don't inherently promote art integration unless paired with creative tasks.

Hence, the correct answer is Projects and Portfolios.

CONCEPT:

Observation vs Inference

• Observation: Information gathered directly through the senses or instruments (e.g., measuring, seeing, feeling).
• Inference: A logical conclusion or interpretation drawn from known facts, experiences, or observations.

EXPLANATION:

• Statement S1: "The normal temperature of the human body is 37°C."
• This value (37°C) is not obtained from a single measurement but derived as an average of several scientific observations.
• Therefore, it is a scientific conclusion or inference, not a simple observation.
• Statement S2: "Heat flows from a body at a higher temperature to a body at lower temperature."
• This is based on the Second Law of Thermodynamics — a general principle derived from repeated experimental results.
• Hence, this too is an inference, not a direct observation.

Therefore, both S1 and S2 are inferences.

Open Book Assessment is an approach where students are allowed to refer to textbooks or other resources while attempting an exam. It is designed to evaluate higher-order thinking, application of knowledge, and conceptual understanding rather than rote memorization.

Key Points The core purposes of an open book assessment in Science include:

• Reducing test anxiety and fear by allowing access to learning materials.
• Assessing conceptual understanding, critical thinking, and the ability to apply concepts to new situations.
• Providing an opportunity for learners to explore their books deeply, identify relevant information, and interpret it meaningfully.

Hint

• ​ Using open-book assessment simply to score more marks contradicts its real educational intent.
• If students approach it only to gain easy marks, they may not engage in meaningful thinking or problem-solving. This defeats the purpose of encouraging deep learning and critical analysis.

Hence, to score more marks in tests should not be the purpose of open book assessment in Science.