Mathematics and Science PYQs

The correct answer is Due to production of Alcohol.

Explanation:

• Yeast are single-celled organisms that respire anaerobically.
• The release of carbon dioxide, a byproduct of anaerobic respiration, caused the dough to rise.
• Glucose is broken down in anaerobic respiration to produce energy, carbon dioxide, and alcohol.
• Because of the alcohol production, the dough had a sour smell.
• A small amount of sugar is added to the dough because yeast feeds on the sucrose in it and produces carbon dioxide, speeding up the fermentation process.
• When yeast is added to the dough, it consumes the sugars present in the dough and undergoes fermentation.
• As a result of this fermentation process, the yeast converts the sugars into carbon dioxide gas and alcohol.
• The carbon dioxide gas causes the dough to rise, resulting in a fluffy texture, while the alcohol produced during fermentation can lead to the sour smell.

Concept:

• The circulatory system, also known as the blood vascular system, consists of a muscular chambered heart, a network of closed branching blood vessels, i.e. arteries, veins, and capillaries, and blood, circulating fluid.
• The heart is a muscular pumping organ, situated in the thoracic cavity in between the two lungs.
• Arteries carry oxygenated blood from the heart to the different tissues and veins carry deoxygenated blood from the tissues to the heart.
• While the pulmonary artery and pulmonary vein carry deoxygenated blood and oxygenated blood respectively.

Explanation:

S1: Blood flows in only one direction in arteries.

• Blood flows in only one direction in arteries.
• The wall of arteries is thick and arteries carry oxygenated blood with a high pressure.
• Thus, this statement is true.

S2: Arteries have valves. 

• Arteries do not need valves because the pressure from the heart is so high that blood can only flow in one direction.
• Thus this statement is false.

Hence, the correct option is (3) S₁ is true but S₂ is false.

The correct answer is (A) will be more effective.

Explanation:

(A): Exhaust fan is fitted on the wall near the ceiling in the kitchen. (CORRECT)

• When the exhaust fan is fitted on the wall near the ceiling in the kitchen, it is indeed the more effective option for expelling heat from the kitchen because:
• Hot air naturally rises, and by placing the exhaust fan near the ceiling, it allows the fan to capture and expel the hot air more efficiently.
• As the hot air rises towards the ceiling, the exhaust fan can quickly draw it up and out of the kitchen, leading to better ventilation and heat removal.
• This helps in maintaining a cooler and more comfortable environment in the kitchen.

(B): Exhaust fan is fitted next to window of the kitchen. (INCORRECT)

• While fitting the exhaust fan next to the window can still help with ventilation, it may not be as effective in expelling heat from the kitchen compared to the exhaust fan is fitted on the wall near the ceiling in the kitchen.

The correct answer is 4 t1 sec.

Explanation:

• In a simple pendulum, the time period (T) is the time taken for one complete oscillation from one extreme position to the other and back to the starting position.
• It is determined by the length of the pendulum and the acceleration due to gravity (g).
• The distance between the mean position and the extreme position = D
• T² ∝ d
• For a simple pendulum,
• Time taken by the bob to move a distance D/4 = t₁ seconds.
• t₁² ∝ D/4
• 16t₁ ∝ D
• Time taken by the bob will be 16 t1 sec.

The Correct answer is Slopes in (A) and (B) will be equal 

Concept:

• The distance-time graph is steeper for faster objects.
• In a distance-time graph, the gradient of the line is equal to the speed of the object.
• The distance-time graph is a straight line then the motion is uniform.
• By calculating the slope of the graph, speed can be calculated.
• Speed and distance are scalar quantities.
• Displacement and velocity are vector quantities.

Explanation:

• A slope in a distance-time graph represents speed. The speed, or slope, can be calculated by taking the ratio of the change in distance to the change in time. Thus, in a distance-time graph, a steeper line corresponds to a higher speed.

For Table A:

• The speed can be calculated by (final distance-initial distance)/(final time-initial time) = (40-0)/(4-0) = 40/4 = 10 units/time.

For Table B:

• The speed can be calculated in the same way, (120-0)/(12-0) =120/12 = 10 units/time.
• So, we can say that the slopes of both A and B are equal, as they both have the same speed of 10 units/time. Hence, the correct answer is Slopes in (A) and (B) will be equal.

Important Points

It's important to note that this doesn't mean they've traveled the same distance, just that their speeds are the same

The correct answer is Size of image will increase.

Concept:

Centre of curvature

• A lens, either a convex lens or a concave lens, has two spherical surfaces.
• Each of these surfaces forms a part of a sphere.
• The centres of these spheres are called centres of curvature of the lens.
• It is represented by C.

Explanation:

• When the object is positioned beyond the center of curvature of a convex lens and the thickness of the lens is reduced, the size of the image formed will increase.
• This occurs because reducing the lens thickness decreases the focal length of the lens.
• As a result, the image moves closer to the lens, and its size increases compared to the original when the object was at the same distance from the lens.

The correct answer is (A) and (B).

Concept:

Sound

• Sound is a form of energy that produces a sensation of hearing in our ears.
• Sound is produced by vibrating objects.
• The matter or substance through which sound is transmitted is called a medium. It can be solid, liquid, or gas.

Light

• Light is a form of energy that allows us to see.
• Light comes from a source and bounces off objects that our eyes perceive, and our brain processes this signal, allowing us to see.​
• Light moves slowly in a denser optical medium and fast in optically rarer medium.

Explanation:

(A) Vibrations are necessary for producing sound - (TRUE)

• Sound is produced due to vibrations in a medium.
• When an object vibrates, it creates mechanical disturbances in the surrounding medium, which then propagate as sound waves.

(B) Sound Travels slower than light - (TRUE)

• Sound travels at a slower speed compared to light.
• The speed of sound depends on the medium through which it travels, and in general, it travels much slower than the speed of light.

(C) Both light and sound require a medium for propagation - (FALSE)

• Sound does require a medium for propagation, as it is a mechanical wave that needs a material medium (such as air, water, or solids) to travel through.
• However, light is an electromagnetic wave, and it can travel through a vacuum (absence of a medium) and does not require a material medium for propagation.

The correct answer is 4) Friction acting on M1 and M2 is zero

Key Points

• Frictional force is the force that opposes the relative motion or tendency of such motion of two surfaces in contact.
• In this scenario, if the blocks are simply lying on a cemented floor and not being subjected to any external forces attempting to move them, then there will be no frictional force acting on them.
• Friction comes into play only when there is an attempt to move one surface over another.
• Since neither M1 nor M2 is moving or attempting to move, the static friction force acting on both will be zero.

Additional Information

• Static friction acts on stationary objects and prevents them from moving. It only exerts a force when there is an applied force attempting to move the object.
• If no external force is applied, the static friction force is zero.
• For friction to exist, there must be relative motion or an attempt to slide one object over another.
• Therefore, in the absence of any applied force attempting to move M1 or M2, the friction acting on both blocks remains zero.
• This explanation assumes no external forces are being applied and the blocks are in equilibrium.

The correct answer is Step A-Inflates; Step B-deflates.

Explanation:

Step-A (Hot water):

• When the plastic bottle with the balloon on its mouth is placed in hot water, the air inside the bottle and the balloon will heat up.
• As the air molecules gain kinetic energy, they will move faster and spread out, causing the air inside the bottle and the balloon to expand.
• Consequently, the balloon will inflate and get larger in size.

Step-B (Cold water):

• After the bottle with the inflated balloon is taken out of the hot water and placed in cold water, the air inside the bottle and the balloon will cool down.
• When a gas cools, its particles lose kinetic energy and move closer together, leading to a decrease in volume.
• As a result, the air molecules inside the bottle and the balloon will contract.
• Consequently, the balloon will deflate and return to its original size as the air inside it becomes colder.

Thus, the balloon will initially inflate in step-A (hot water) and then deflate in step-B (cold water).

The correct answer is option 3.

Explanation:

Characteristics of a Fuse:

 

• Thin Wire:
• Fuses are typically made from thin wires or ribbons of a specific material.
• The thin wire ensures that the fuse heats up quickly and melts when excessive current flows through it.
• High Resistivity:
• The material used in the fuse wire has high resistivity, meaning it resists the flow of electric current.
• This resistance causes the wire to heat up when current passes through it.
• Low Melting Point:
• A fuse is made from a material with a low melting point to ensure that it melts quickly and breaks the circuit when excessive current flows through it.​

Additional Information 

A fuse wire is a safety device used in electric circuits. Its job is to melt and break the circuit if too much current flows, to prevent damage to appliances or danger like fire.

 

Now, here’s the important part:

 

The material used to make a fuse wire (like aluminium or tin) has low resistivity. That means it lets electric current flow easily. In other words, it’s a good conductor.

 

So, how can a wire made of a good conductor still have high resistance?

 

The answer lies in the shape and size of the wire:

 

R = ​ ρ(L/A)

 

• A longer wire has more resistance.
• A thinner wire (small cross-sectional area) also has more resistance.

 

So, even though the material itself conducts electricity well, the wire is made long and thin to give it high resistance. This way, when too much current flows, the wire heats up quickly and melts, breaking the circuit.

 

The resistance is made high by virtue of the dimensions or shape of the wire such as high length and low cross sectional area. you might get confused by the property of low resistivity of the material and think thus, that the fuse wire must also have low resistance.

The laboratory task described appears to have students apply a concept they've already learned to observe a specific phenomenon (the rusting of iron in moist air). 

Key Points

• Deductive reasoning starts with a general theory or hypothesis and examines the possibilities to reach a specific, logical conclusion. In this scenario, the general theory (that iron rusts when exposed to moist air) is already known, and the laboratory work is designed to test this specific theory. So, this statement is true.
• Since the teacher has already discussed the concept of corrosion thoroughly in class, the students have a clear understanding of what they are expected to observe in the laboratory task.
• Engaging students in hands-on experiments help solidify theoretical knowledge by linking it with practical observation. So, this statement is true as well.
• In this task, the students are not making broad generalizations from specific observations. The generalization (the understanding of corrosion) already exists, and they are not arriving at it through observation. So, this statement is not true.

Hence, we can conclude that It allows students to use observations to arrive at a generalization that is not true regarding the laboratory task described above.

Scientific theories are well-substantiated explanations of some aspects of the natural world that are based on a body of evidence that has been repeatedly confirmed through observation and experiment.

Key Points

• (A) Scientific theories give a systematic explanation of natural phenomena: Scientific theories are frameworks for understanding natural phenomena, based on a body of evidence.
• (B) Scientific theories make huge demands on our imagination for their understanding: Many scientific theories can indeed be complex and abstract, requiring imaginative and creative thinking to understand, develop, or extend.
• (C) Scientific theories should predict new phenomena which are verifiable by experimentation: As previously mentioned, this statement is true. The ability to make predictions that can be tested is a vital part of scientific theories.
• (D) Scientific theories are always tentative: In science, theories are open to revision, refinement, or rejection based on new evidence or better interpretations.

Hence, we can conclude that all (A), (B), (C) and (D) statements are correct.

Divergent questions are those that allow for multiple possible answers and encourage creative thinking. 

Key Points

• Explain how Carbon dioxide is able to control fires: This question requires a specific explanation based on established scientific principles.
• Is friction a friend or foe?: It might lead to a discussion but generally within defined boundaries, such as understanding where friction is useful (like in walking) or detrimental (like in mechanical wear).
• Why objects floating in fluids must have special shapes?: This question also leads to specific answers based on principles of fluid dynamics and buoyancy.
• What will happen if we go on cutting trees?: This is the divergent question among the options. The reason it's considered divergent is that it invites a broad and multifaceted exploration of the topic.

Hence, we can conclude that "What will happen if we go on cutting trees?" is a divergent question.

Science is an interdisciplinary area of learning reflects how different branches of science interconnect and work together to explain phenomena comprehensively. The given excerpt demonstrates the integration of thermodynamics with real-world applications such as cooling systems and chemical reactions, showcasing the interdisciplinary nature of science.

• The excerpt highlights the application of thermodynamics in everyday life, such as cooling a room using an air conditioner, and in natural processes like photosynthesis.

Key Points

• Interdisciplinary nature of science: Science does not exist in isolation; it integrates knowledge from different fields like physics, chemistry, biology, and engineering to solve problems and understand phenomena.
• Thermodynamics: The excerpt explains how thermodynamics governs physical processes, such as cooling and phase equilibrium, and applies to biological processes like photosynthesis.
• Real-world applications: The use of thermodynamics in air conditioning systems reflects the practical application of scientific principles in technology.
• Unity of disciplines: The interconnectedness of physical and biological sciences demonstrates how interdisciplinary approaches enhance our understanding of complex systems.

Hint

• Science is a socio-cultural endeavor: Although science impacts society and culture, the excerpt primarily focuses on interdisciplinary learning rather than socio-cultural aspects.
• Science is tentative in nature: While scientific knowledge can evolve, the excerpt emphasizes established principles of thermodynamics rather than their tentative nature.
• Science demands perseverance: This concept relates to the effort required in scientific research, which is not the primary focus of the excerpt.

Hence, the correct answer is 'Science is an interdisciplinary area of learning'.

Asking questions before starting a lesson can be a valuable way to engage students, assess their prior knowledge, and identify any misconceptions that they may have.

Key Points

• To motivate students to participate in the process of learning. The questions are open-ended and require students to think about their own experiences. This can help to motivate students to participate in the learning process and to think about the concepts being discussed.
• To relate scientific concepts to student's previous knowledge. This can help students to relate the new concepts being introduced to their existing knowledge, which can make it easier for them to understand the new concepts.
• To know students’ alternative conceptions if any. This can help the teacher to identify any misconceptions that students may have about these processes.

Hence, we can conclude that statements (A), (B) and (C) are the correct answers.

Discussion refers to interactive communication between students, or between the teacher and students, about scientific concepts, theories, or experimental results.

Key Points

• (S1): suggests that discussing controversial scientific issues promotes argumentation and learning, which is generally accepted to be true.
• Such discussions typically encourage critical thinking, promote the analysis and understanding of complex concepts, and enhance learning.
• (S2): states that argumentation helps in building explanations, models, and theories in science that promote learning.
• This is also true, as argumentation is a critical part of the scientific process, helping to refine ideas, theories, and explanations.
• Controversial issues stimulate debate, engage interest, and promote a deeper understanding of the topic.
• In other words, the argumentation that comes from controversy isn't necessarily about building new models and theories but about understanding existing ones better.

Hence, we can conclude that Both S1 and S2 are true but S2 is not the correct explanation for S1.

Discussion refers to interactive communication between students, or between the teacher and students, about scientific concepts, theories, or experimental results.

Key Points

• (A) Express to students that their ideas are valued: By inviting students to discuss the question, the teacher is showing an interest in their ideas, and by asking them to justify their answers in a group project, the teacher is placing value on their ideas and their ability to support those ideas.
• (B) Guide students to appreciate multiple perspectives: In asking students to collect more information and justify their answers, the teacher indirectly guides them to explore multiple perspectives.
• (C) Emphasizes the importance of the tentativeness of science to students, which might not be directly achieved in this activity.
• (D) Encourage students to frame questions and browse a variety of reading materials: The project work likely involves researching different sources of information, which will inherently encourage students to frame additional questions and browse a variety of reading materials.

Hence, we can conclude that statements (A), (B), and (D) could be the objectives of the above task.

Inference is a cognitive process where conclusions are drawn based on evidence, reasoning, and context.

Key Points

• (A) Aluminum is a good conductor of electricity: This statement is based on repeated observations and tests that show aluminum conducts electricity efficiently.
• Therefore, it's considered an inference because it's a generalized conclusion based on experimental data.
• (B) Like charges repel and unlike charges attract each other: This is a fundamental principle of electromagnetism known as Coulomb's law.
• This principle is not directly observed but inferred from experiments and is used to explain the behavior of charged particles. Therefore, it's also considered an inference.

Hence, we can conclude that (A) - Inference; (B) - Inference.

Science education aims to equip students with the knowledge, skills, attitudes, and competencies necessary to understand and interpret the natural and physical world.

Key Points

• (A) Appreciate issues at the interface of science, society & technology: This is highlighted in the excerpt as it discusses the role and importance of biosphere reserves, and how human factors like increasing population and introduction of new species can affect natural habitats.
• (B), "Understand methods of generation of scientific knowledge," is not explicitly mentioned in the excerpt. While it's implied that scientific knowledge is being shared and discussed, there's no direct mention of how that knowledge is generated.
• (C) Raise environmental concerns: The excerpt directly addresses this as it discusses the destruction of habitats and the conservation of biodiversity, both of which are major environmental concerns.
• (D), "Nurture the aesthetic sense and creativity in science and technology," is also not highlighted in the given excerpt. There is no direct focus on the aesthetic or creative aspects of science and technology in the discussion about biosphere reserves and biodiversity.

Hence, we can conclude that statements (A) and (C) are the objectives of science education based on the above excerpt highlight.

The nature of science is a complex and multifaceted concept. It refers to the characteristics of science, including its methods, goals, and limitations.

Key Points

• (A), "Science is socially and culturally embedded," is not explicitly illustrated in the excerpt. While scientific understanding may be influenced by social and cultural contexts, the excerpt doesn't provide specific information on how the social and cultural context influenced the development of theories about light.
• (B) Science is advanced through the creativity and imagination of scientists: The excerpt directly demonstrates this through the differing proposals of Huygens and Newton regarding the nature of light.

Each used their creativity and imagination to develop a model to explain the observed phenomena.

• (C) Science is tentative in nature: This is also illustrated in the excerpt, which shows how the understanding of light has evolved over time. Initially, Huygens proposed a wave model of light, and later Newton proposed a particle model.
• (D), "Science progresses through a fixed scientific method," is also not directly supported by the excerpt. The changes in understanding depicted do show progression in scientific knowledge, but there's no indication that this progress followed a rigid, fixed method.

Hence, we can conclude that statements (B) and (C) aspects of the nature of science are illustrated by the above excerpt.