Mathematics and Science PYQs

The Correct answer is Blue zone.

Explanation:

• Black Zone: This is the zone closest to the source of the fuel. It is the coldest part of the flame and does not have enough oxygen for complete combustion to occur. That’s why it's not advisable to use this zone for heating purposes.
• Yellow Zone: This is a moderately hot part of the flame but it does not receive enough oxygen for complete combustion and thus produces soot (carbon particles).
• Blue Zone: The blue zone is the hottest part of the flame and is best for heating purposes. In this zone, combustion is complete due to the presence of sufficient oxygen, and it is the cleanest part of the flame as there is complete combustion of the fuel with no production of soot. Hence, Anita should use the blue zone of the flame to boil the water quickly.
• Either Blue Zone or Yellow Zone: Although the yellow zone is hotter than the black zone, it is not as hot as the blue zone. Additionally, it doesn't burn as cleanly. Therefore, it's not the optimal choice for quick and efficient heating.

Hence, the ideal part to position and heat the test tube would be in the blue part of the flame, where the heat is maximum and combustion is complete.

The Correct answer is (B) and (C).

**Explanation:**​

• Curd: Curd contains lactic acid, which is produced as a result of the fermentation of milk. Lactic acid can donate hydrogen ions (H⁺), hence displaying an acidic character.
• Glucose: Glucose (C₆H₁₂O₆) is a sugar, and its molecule does not contain any ionizable hydrogen.

No hydrogen ions (H⁺) are released when it is dissolved in water, so glucose solutions are not acidic.

• Alcohol: An alcohol (like ethanol, methanol, etc.) has no ionizable hydrogen and therefore, does not release hydrogen ions when placed in solution. Thus, it doesn't show the acidic character.
• Amino Acid: Amino acids have a carboxyl group (-COOH) and an amino group (-NH2). The carboxyl group can donate a hydrogen ion (H⁺) and hence has acidic properties.

Therefore the solutions of Glucose (B) and Alcohol (C) do not show acidic behavior because they don't release hydrogen ions when dissolved in water.

The Correct answer is (B) → (D) → (C) → (E) → (A) → (F).

Explanation:

• (B) Female silk moths lay eggs: This is the first step in the process of silk production. The female moth lays hundreds of eggs at a time.
• (D) Eggs are warmed to a suitable temperature for the larvae to hatch: The laid eggs require a suitable temperature condition to stimulate the larva inside to hatch. This process is called incubation.
• (C) The larvae or silkworms are kept in clean trays along with fresh mulberry leaves: After hatching from the eggs, the silkworm larvae or caterpillars are kept in trays and fed with fresh mulberry leaves. Silkworms eat continuously for about 25-30 days.
• (E) After 25 - 30 days, caterpillars stop eating and start spinning cocoons: Once the silkworms have consumed enough and grown to their full potential, they stop eating and begin to spin a protective cocoon.
• (A) Cocoons are kept under the sun or boiled in water: Before the adult moth can emerge, the cocoon is subjected to the sun or boiled in water. This prevents the moth from breaking the silk filament in the cocoon and ensures long, unbroken fibers.
• (F) Fibers are taken out from cocoons: Finally, the silk fibers (also known as silk threads) are carefully taken out from the cocoon. This is called reeling the silk and is a delicate process because silk fibers are extremely fine and lustrous.

Hence the correct sequence is Eggs laid (B) → Eggs warmed (D) → Larvae fed (C) → Cocoons formed (E) → Cocoons processed (A) → Silk taken out (F).

The Correct answer is swallowed and partially digested.

Explanation:

• "Cud" is a term used to refer to the food that ruminant animals, such as cows and deer, regurgitate and re-chew. The process goes like this:
• Ruminants swallow their food without fully chewing it first. This unchewed food (now referred to as "cud") goes to the rumen, the first of their stomach's four compartments. In the rumen, it is soaked and processed by bacterial action, leading to its partial digestion.
• Later, this partially digested food, or "cud", is regurgitated back into the animal's mouth, where it is chewed thoroughly to break it down further before it is swallowed again for further digestion.

Thus, the 'cud' is swallowed and partially digested.

Additional Information

• Grazing animals like cows, buffaloes, and deer are known as ruminants.
• Cows, buffaloes, and other ruminants (grass-eating animals) swallow the food continuously even when they are not eating.
• This is essentially an adaptation that these animals have developed in order to consume food as quickly as possible while avoiding predators.
• Actually, they quickly swallow the grass and store it in a part of the stomach called the rumen.
• Here, the food gets partially digested and is called cud.
• But later the cud returns to the mouth in small lumps.
• In this process, these animals again start chewing cud. This process is called rumination.
• The grass is rich in cellulose, a type of carbohydrate.
• In ruminants like cattle deer, etc, bacteria present in the rumen help in the complete digestion of cellulose.

The Correct answer is Methyl orange

Explanation:

• Methyl Orange: This is an indicator that turns red in acidic conditions and yellow in basic conditions. This can help identify if a solution is acidic or basic.
• This is a common pH indicator that changes color based on the pH of the solution it is added to. In a pure substance, methyl orange appears red. However, under acidic conditions ( in a solution with a pH of less than 7), its color remains red. In neutral conditions (pH of 7), it appears orange. Under basic conditions (in a solution with a pH greater than 7), it appears yellow.
• China Rose: The color of a China rose or Hibiscus rosa-sinensis solution changes in the presence of an acid or a base. It turns dark pink in basic solutions and green in acidic solutions.
• Phenolphthalein: Phenolphthalein is a chemical compound often used as a pH indicator in titrations. For acidic solutions, it remains colorless and turns pink in basic solutions [0].
• Turmeric Solution: Turmeric is a natural indicator that changes color in acidic and basic conditions. When added to an acidic solution, it will remain yellow, in a neutral solution, it will remain yellow but will turn red or brown in a basic solution.

Note: In the official answer key of the CTET they have given option 1,2 are correct, but according to questions option 1 is correct.

The Correct answer is Oxidation of carbon to carbon dioxide.

Explanation:

• Absorption of light energy by chlorophyll: This does happen during photosynthesis. Chlorophyll in the chloroplasts of plant cells absorbs light energy from the sun, which is the first step in photosynthesis.
• Conversion of light energy into chemical energy: This is another core process of photosynthesis. The light energy, once absorbed, is used to convert water and carbon dioxide into carbohydrates (specifically, glucose) -- a form of chemical energy.
• Oxidation of carbon to carbon dioxide: This Does not happen during photosynthesis. Instead, this process occurs during cellular respiration, where glucose (made by photosynthesis) is broken down to release energy, and carbon dioxide is a byproduct. In photosynthesis, carbon dioxide is consumed, not produced.
• Reduction of carbon dioxide to carbohydrates: This process also happens during photosynthesis. Under the influence of sunlight, carbon dioxide undergoes reduction, i.e., it gains hydrogen to form carbohydrates (glucose).

Therefore, the conversion of carbon to carbon dioxide, or the "oxidation of carbon to carbon dioxide"

The Correct answer is More heat will be produced in the case of B.

Concept:

• The amount of heat produced in a wire-carrying current depends on the wire's resistance. Joule's Law of Heating states this mathematically.
• H = I2RT,
• where H is heat energy, I is current, R is resistance, and T is time.
• Resistance is given by the expression R = ρ× (L/A)
• where ρ is the resistivity, L is the length of the wire, and A is the cross-sectional area of the wire.

Explanation:

• The amount of heat produced in a resistor (here, the wires A and B) when a current I is flowing through it for time t is given by Joule's law of heating, H = I²Rt, where 'R' is the resistance of the resistor.
• Resistance (R) is directly proportional to the length (l) of the conductor (assuming the cross-sectional area (A) and the material of the conductor are constant), that is, R ∝ l. Thus, a wire of greater length will have greater resistance [0].
• Wire A has a length of 10 cm, and wire B has double that length, 20 cm, while the thickness of the two wires is the same. This means the resistance of wire B will be more than that of wire A.
• With a higher resistance in wire B, according to Joule's law of heating, more heat will be produced if the same current flows for the same amount of time.

Therefore, more heat will be produced in case B.

The Correct answer is The bottle will collapse (contract) due to    decrease in pressure inside the bottle.

Explanation:

• The pressure exerted by a gas is due to the continuous, random, and rapid motion of a large number of molecules against the container walls. When you cool a gas (that's what happens when an item is placed in a refrigerator), the kinetic energy of its molecules decreases, causing them to move slower. This reduces the pressure of the gas inside the container.
• If a closed container filled with gas (in this case, a plastic bottle filled with air) is placed in a refrigerator, the pressure inside the container decreases due to the drop in temperature. On the other hand, the ambient pressure outside the refrigerator (and therefore outside the bottle) remains the same as it was before the bottle was refrigerated.
• As the air inside the bottle cools down, the pressure inside the bottle decreases. Since the pressure outside the bottle doesn't change, there is now a higher pressure outside the bottle than inside it.
• This pressure difference causes the bottle to contract or collapse as the air particles inside the bottle take up less space due to a decrease in their kinetic energy.

The Correct answer is (A), (C) and (D).

• (A) An object can be seen only if it reflects light. This statement is TRUE. We can see objects when light that is reflected from their surfaces enters our eyes. This is a basic principle of optics.
• (B) A convex lens always produces a real image. This statement is FALSE. A convex lens can produce either a real or virtual image, depending on the object's position relative to the lens. When the object is at or beyond the focus of the lens, a real image can be formed on a screen.
• But if the object is between the lens and the focus, the lens produces a virtual, enlarged, and upright image.
• (C) A concave mirror can be used to produce an enlarged and erect image. This statement is TRUE. When an object is placed very close to (inside the focus of) a concave mirror, the mirror creates a virtual, enlarged, and erect image.
• (D) When the size of the image formed by a concave lens is smaller than the object, the image orientation is erect. This statement is TRUE. Regardless of the object's position, a concave lens will always produce a diminished, virtual, and erect image.

Thus, the correct pair of true statements is (C) and (D).

Note:

In the official answer key option 3 is given correct, but according to questions option 4 is correct.

CONCEPT:

Behavior of Dry Hydrochloric Acid (HCl) and Litmus Paper

• Acids and Ionization: Acids like hydrochloric acid (HCl) dissociate to produce H⁺ ions when they dissolve in water. These H⁺ ions are responsible for the characteristic properties of acids, such as changing the color of litmus paper.
• Dry HCl Gas: When HCl is in its gaseous or dry form, it lacks water molecules, which are essential for HCl to dissociate into H⁺ and Cl^- ions. As a result, dry HCl gas does not release H⁺ ions, and hence, it does not behave as an acid in the absence of moisture.
• Litmus Paper and Ion Requirement: Litmus paper only changes color in the presence of H⁺ ions (for acidic conditions) or OH^- ions (for basic conditions). Without these ions, the litmus paper does not react and remains unchanged.

Explanation of Statements:

• Statement S1: "Dry Hydrochloric Acid does not change the colour of dry litmus paper."
• This statement is true because, in the absence of moisture, dry HCl cannot release H⁺ ions, which are necessary for litmus color change.
• Statement S2: "Litmus paper changes color only in the presence of H⁺ ions and OH^- ions."
• This statement is true. Litmus paper acts as an acid-base indicator, which changes color specifically due to the presence of hydronium ions (H⁺) or hydroxide ions (OH^-).

CONCLUSION:

The correct option is:

• Option 1: Both S1 and S2 are true and S2 is the correct explanation for S1.

Science is always evolving and changing as new evidence is gathered.

Key Points

• Newton's theory of gravity was a great advance for its time, but it was eventually found to be incomplete.
• Einstein's theory of relativity was able to explain phenomena that Newton's theory could not, and it is now the accepted theory of gravity.
• The teacher's remark highlights the tentativeness of science.

Hence, we can conclude that the teacher highlights the tentativeness of Science.

Additional Information

• Subjectivity in science refers to the fact that scientists are human beings and are therefore susceptible to biases and errors.
• Cultural embeddedness of science refers to the fact that science is shaped by the culture in which it is practiced.
• Value-neutrality of science refers to the fact that science is not supposed to be influenced by values.

Hypothesizing is the ability to make a guess about what might cause something to happen.

Key Points

• Hypothesizing is a critical skill for scientific inquiry. It allows scientists to explain phenomena and to test their explanations.
• The students observed that the bulb did not glow.
• They can hypothesize that the bulb did not glow because the circuit had no power.
• They can then test this hypothesis by checking the power supply to the circuit.

Hence, we can conclude that the teacher trying to develop Hypothesizing skill among her students.

The best task/strategy to challenge students' alternative conception is to ask students to do an activity that involves grinding a few spices in a mixer grinder and observing the change in temperature during the process.

Key Points

• This activity is a good way to challenge students' misconceptions because it is something that they can do themselves and see the results for themselves.
• When students grind spices in a mixer grinder, they generate heat. This is because the friction between the spices causes them to heat up.
• Students can observe this change in temperature by touching the sides of the mixer grinder or by feeling the spices after they have been ground.

Hence, we can conclude that option 3 is the correct answer.

Inquiry in science is a process of asking questions, gathering evidence, and drawing conclusions.

Key Points

• It can involve laboratory work, but it can also involve other types of activities, such as field research, reading, and data analysis.
• Laboratory work is just one part of the inquiry in science.
• It is a valuable tool for gathering evidence, but it is not the only way to gather evidence.
• Scientists also gather evidence through field research, reading, and data analysis.

Hence, we can conclude that it involves laboratory work only is not true regarding inquiry in Science.

Constructivism is a theory of learning that states that learners actively construct their own knowledge by interacting with the world around them.

Key Points

• Learners do not simply memorize facts, but they make sense of the world by building their own mental models.
• Learners' naive ideas may be incomplete or inaccurate. In some cases, learners' naive ideas may be scientifically accurate.
• However, even in these cases, it is important to build on learners' naive ideas rather than simply dismissing them.
• Learners are more likely to be successful in learning new concepts if they can relate them to their existing knowledge.

Hence, we can conclude that the learners' naive ideas are scientifically incorrect and should be addressed is not an underlying assumption of a 'Constructivist' approach in Science.

Objectives focus on developing students' understanding of scientific concepts and principles. They also aim to develop students' critical thinking skills and their ability to solve problems.

Key Points

The excerpt from the NCERT Science Textbook for Class VII, Chapter: Forests: Our Lifeline, highlights the following objectives of science education:

• To relate to the environment, both local as well as global. The excerpt shows how forests are not just home to plants and animals, but also to people.
• It also shows how forests provide food, shelter, water, and medicines to people. This highlights the importance of forests for the environment, both locally and globally.
• To view science as a social enterprise. The excerpt shows how people depend on forests for their livelihood.
• This highlights the importance of science for society. Science can be used to understand the environment and to develop solutions to environmental problems.

Hence, we can conclude that statements (B) and (D) are the objectives highlighted in the above excerpt.

A principle is a general statement that explains a natural phenomenon. It is based on observation and experimentation, and it can be used to make predictions about other phenomena.

Key Points

• The statement "Mitochondria is the powerhouse of the cell" is a principle because it explains the role of mitochondria in cellular respiration.
• Mitochondria are organelles that produce energy for cells.
• They are often called the "powerhouses of the cell" because they produce so much energy.

Hence, we can conclude that this statement represents a Principle.

Scientific theories and concepts are essential for understanding the natural world. They allow us to make sense of the world around us and to predict how it will behave.

Key Points

• S1: Scientific theories may be incommensurable. This means that two scientific theories may be so different that they cannot be compared or judged against each other.
• This is because the meanings of the concepts used in the two theories may be different.
• S2: Meanings of scientific concepts in a theory depend on the theory to which they belong.
• This means that the meaning of a concept in one theory cannot be simply transferred to another theory.
• For example, the concept of "mass" in Newtonian mechanics has a different meaning than the concept of "mass" in special relativity.

Hence, we can conclude that both statements S1 and S2 are correct and S2 is the correct explanation for S1.

An inclusive science classroom is one that is designed to meet the needs of all learners, regardless of their background, abilities, or interests.

Key Points

• Designing uniform educational approaches for parity among learners is not inclusive because it does not take into account the individual needs of learners.
• All learners are different, and they learn in different ways. A one-size-fits-all approach to education will not be effective for everyone.
• The teacher should use a variety of teaching-learning approaches to promote learning, engage learners in group work and collaborative learning, and develop individualized educational programs based on the level of performance of learners.

Hence, we can conclude that Teacher designs uniform educational approaches for parity among learners do not characterize an inclusive Science classroom.

An alternative conception is a belief or idea about a scientific concept that is different from the scientific consensus.

Key Points

• The common alternative conception that you are likely to encounter while teaching pressure to learners of Class VIII is Pressure of a gas increases with a decrease in temperature.
• This alternative conception is incorrect because, according to the ideal gas law (PV = NRT), the pressure of a gas is directly proportional to its temperature when other variables are held constant.
• Therefore, as the temperature of a gas decreases, its pressure would also decrease, assuming other factors remain the same.
• It's important to address this misconception and help students understand the correct relationship between pressure and temperature in gases.

Hence, we can conclude that the pressure of a gas increases with a decrease in temperature is a common alternative conception.