Mathematics and Science PYQs

The correct answer is A - iii, B - iv, C - i, D - ii

Explanation;

 

• Chalk powder and water: Filtration is the method that can be used to separate chalk powder from water.
• Filtration involves passing a mixture through a filter medium that allows the liquid component (water) to pass through while retaining the solid component (chalk powder).
• Camphor and salt: Sublimation is the method that can be used to separate camphor from salt.
• Sublimation is a process in which a solid directly changes into a gas without going through the liquid state.
• Camphor, being a volatile substance, can undergo sublimation under suitable conditions, leaving the non-volatile salt behind.
• Sugar and water: Crystallization is the method that can be used to separate sugar from water. Crystallization involves evaporating the water from the mixture, causing the dissolved sugar molecules to come together and form crystals.
• Fat and cream: Centrifugation is the method that can be used to separate fat from cream.
• Centrifugation involves spinning the mixture at high speed, causing the denser component (in this case, fat) to separate and settle at the bottom of the container, while the lighter component (cream) remains on top.

The Correct answer is Both (A) and (R) are true and (R) is the correct explanation of (A).

Concept:

• The matter is anything that has mass and volume.
• There are 3 types of matter-
• Solid- The matter in which the particles are closely packed together.
• Liquid - The matter in which the particles are less closely packed than solid and more than gas.
• Gases - In this state of matter, the constituent particles are free for random movement in all directions.

Explanation:

• The intermolecular forces of attraction are strong in solids because the constituent particles are closely packed. So, the shape and size of the solids do not easily change.
• In liquid, the intermolecular forces of attraction in between the molecules are weaker than in solid because the constituent particles are less closely packed. So, the shape and size of the liquids are easily changed.
• The intermolecular spaces between solids are absent because they are closely packed to each other.
• Solid can not be compressed because the particles can not move.

Important Points 

The Correct answer is Bases give pink colour in phenolphthalian.

Concept:

Acids:

• An acid is a molecule or ion capable of either donating a proton (i.e., hydrogen ion, H+), known as a Brønsted–Lowry acid, or, capable of forming a covalent bond with an electron pair, known as a Lewis acid.
• Acids taste sour because of their hydrogen ion concentration while tasting the tongue gains ions and it registers the flavor as sour.
• Acidity can be measured by the pH level of a solution.
• Acids are solutions that have a pH lower than 7.
• The lower the solution or compound on the pH scale, the sourer it tastes due to the high concentration of hydrogen ions.

Bases:

• The base is a substance that dissociates in an aqueous solution to form Hydroxide ions OH−
• A soluble base is called an alkali.
• Bases are solutions that have a pH greater than 7. They release OH- ions in an aqueous solution.
• Bases feel slippery to the touch and they taste bitter.

Explanation:

• When a base is added to phenolphthalein, the solution turns pink due to the alkaline nature of the base.
• Bases are substances that can accept protons (H +) or donate hydroxide ions (OH -) in solution, resulting in an increase in the concentration of hydroxide ions.
• The presence of hydroxide ions in the solution causes the phenolphthalein to change its color to pink.

The correct answer is (i) - testosterone, (ii) - estrogen, (iii) - pituitary.

Explanation:

• The male hormone is testosterone, which is responsible for the development of male characteristics.
• The female hormone is estrogen, which is responsible for the development of female characteristics.
• The gland that secretes hormones to control the production of male and female hormones is the pituitary gland.
• The pituitary gland is often referred to as the "master gland" because it releases hormones that regulate various functions in the body, including the production of other hormones.
• It releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which control the production of testosterone and estrogen in males and females, respectively.

The Correct answer is distance-time graph of a uniformly accelerating object 

Concept:

Uniform Acceleration:

• If an equal amount of velocity increases in equal intervals of time, then the object is said to be in uniform acceleration.
• The acceleration of an object can be zero when it is moving with a constant velocity. Since velocity is constant, there will be no change in velocity and so there will be no acceleration.

Non-Uniform Acceleration:

• If the velocity of the object changes by unequal amounts in equal intervals of time, the object is said to be non-uniform acceleration.

Explanation:

• A distance-time graph of a uniformly accelerating object is NOT a straight-line graph.
• the graph shows a curved line because speed increases over time due to acceleration. The greater the acceleration, the steeper the curve on the graph.
• An object at rest will have a straight-line distance-time graph at zero distance because it is not moving.
• An object moving at a constant velocity will also have a straight-line graph on a velocity-time graph since the velocity does not vary with time.
• An object moving with uniform acceleration will have a straight-line graph on a velocity-time graph because the velocity is increasing steadily. The steepness of the line provides an indication of the acceleration.

The Correct answer is that Non-metallic oxides are basic in nature.

 Concept:

Metals: 

• The elements readily form positive ions (cations) and are called Metals.Ex.→ Na, K, Mg, Fe, Cu, Ag, etc.
• Metals are usually Solid, a good conductor of Heat & Electricity, Malleable, Ductile, and Sonorous, and Have good tensile strength.
• Metals react with oxygen to form their respective Metal Oxides i.e. Metal + Oxides →  Metal Oxides

Non-Metals: 

• Non-Metals form Negative ions by accepting or gaining electrons.
• They are Insulators, Have Lower Tensile Strength, and Dull Appearance.

Explanation:

• To test the acidity and basicity of these Metal Oxides, they are made with water & then react with water, and then tested with litmus paper.
• A basic solution turns litmus to blue whereas an acidic solution turns blue litmus to red.
• Metal Oxides + Water → Metal Hydroxides
• Metal oxides are Basic in nature.
• Some Metal Oxides, for example, Oxides of Aluminum and Zinc show both acidic and basic nature Such Oxides are called Amphoteric Oxides.
• Non-metallic oxides are Acidic in nature. Ex.→ SO2 + H2O → H2SO4 + 2H .
• The basic solution has more OH - ion concentration than the H+ ion.

The correct answer is Shimla.

Explanation:

1) Kochi is a coastal city located in the state of Kerala, South India. It generally has a tropical monsoon climate with high humidity throughout the year. But, the temperatures seem too low to be Kochi, as the maximum temperature there rarely falls below 30°C even in the winter months.

2) Shimla is located in the hilly state of Himachal Pradesh in North India. It has a subtropical highland climate. The city experiences mild summers and cold, snowy winters. The given data could possibly belong to Shimla, as the temperatures for January, February, and March align quite well with Shimla's climate.

3) Karnal is in the state of Haryana in North India and has a hot-summer humid subtropical climate. The summer months (April to June) can get quite hot with temperatures often exceeding 40°C, which is higher than the given data. 

4) Jodhpur: Jodhpur is a city in Rajasthan, India. It has a hot, desert climate, with very hot summers and cool winters. The average maximum temperature in Jodhpur is 38°C, and the average minimum temperature is 20°C. The humidity in Jodhpur is low,

Based on these considerations, it appears that the city that best matches the data is Shimla.

The correct answer is They provide humus to the soil.

Explanation:

• Fertilizers can be inorganic salts: Fertilizers can be either inorganic or organic in nature.
• Inorganic fertilizers are typically derived from minerals or chemical compounds that contain essential plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K), among others. These nutrients are necessary for plant growth and development.
• Fertilizers are rich in plant nutrients: Fertilizers are specifically designed to provide essential nutrients to plants.
• They are formulated to supplement the nutrient content in the soil, thereby promoting healthy plant growth and increasing crop yields.
• The composition of fertilizers varies depending on the specific nutrient requirements of different plants and crops.
• Fertilizers do not provide humus to the soil: Humus is the dark, organic matter that forms as a result of the decomposition of plant and animal residues over a long period.
• It contributes to soil fertility by improving its structure, water-holding capacity, and nutrient retention.
• Organic fertilizers, such as compost or manure, can contribute to the organic matter content and humus formation in the soil, inorganic fertilizers do not provide humus. Inorganic fertilizers mainly focus on supplying specific nutrients to plants.
• Fertilizers are made in factories: Fertilizers, both inorganic and organic, are typically manufactured in factories. Inorganic fertilizers are produced through industrial processes that involve extracting or synthesizing the necessary minerals or chemical compounds to create nutrient-rich formulations. Organic fertilizers, on the other hand, are derived from natural sources such as plants, animals, or waste materials, but their processing and packaging may still occur in factories.

The correct answer is A - iv, B - v, C - ii, D - i, E - iii

Explanation:

• Mouth: The mouth is responsible for the initial stage of digestion. It helps in the mechanical breakdown of food through chewing and the chemical breakdown of starches by the enzyme amylase, which converts starch into sugar.
• Stomach: The stomach is involved in the mechanical and chemical digestion of food. It secretes gastric juices, including hydrochloric acid and enzymes, which help break down proteins and kill bacteria present in the food.
• Liver: Although not directly a part of the digestive tract, the liver plays a crucial role in digestion. It produces bile, a substance stored in the gallbladder and released into the small intestine. Bile aids in the digestion and absorption of fats by emulsifying them into smaller droplets.
• Small Intestine: The small intestine is the main site for digestion and absorption of nutrients. It receives bile from the liver and digestive enzymes from the pancreas.
• The intestinal walls have finger-like projections called villi, which increase the surface area for absorption of digested nutrients into the bloodstream.
• Large Intestine: The large intestine is responsible for the final stages of digestion and the absorption of water and electrolytes from undigested food. It also houses beneficial bacteria that aid in the fermentation of undigested carbohydrates and the production of certain vitamins.

The correct option is: 3) (A) is true but (R) is false

Explanation:

• It is true that synthetic clothes generally dry faster than cotton clothes, the reasoning provided in (R) is incorrect.
• The drying time of clothes depends on various factors such as fabric composition, thickness, and absorbency.
• Synthetic fabrics, such as polyester or nylon, are known to be less absorbent than cotton, which can contribute to faster drying times.
• However, the drying speed is not primarily determined by the presence of large pores in synthetic fabrics.

Cognitive validity is based on the idea that the brain develops over time, and at each stage of development, it is capable of understanding different types of concepts. This is derived from Jean Piaget's theory of cognitive development, which identifies distinct stages that children pass through in their cognitive maturation: Sensorimotor, Preoperational, Concrete Operational, and Formal Operational.

Key Points

Now, the structure of an atom, elements, and compounds are conceptually complex and abstract topics. They belong to a field of study within chemistry, and they require a certain level of abstract thinking and reasoning ability.

• These topics usually require understanding of the abstract concept of sub-microscopic particles (which cannot be seen or touched), symbolic representation, and the ability to visualize in three dimensions, which children develop during their later years, often in the Formal Operational stage (from about age 12 onward).
• Meanwhile, Class VI students (around age 11-12) might be at the Concrete Operational stage. They're typically beginning to think logically about concrete events but might still struggle with abstract concepts.
• Hence, introducing the concept of atom structures and properties of elements at this stage could potentially overtax their cognitive capabilities, preventing effective learning.

Hence, it can be concluded that cognitive validity is the correct answer.

The correct answer is option 2. 

Key Points

• The process skill of observing involves using one's senses to gather information about objects or events. The corresponding indicator in Column B is "Identifying similarities between different objects."
• : Hypothesising is the process of making an educated guess or proposing a possible explanation based on limited evidence or prior knowledge.
• Predicting involves making educated guesses about what will happen in the future based on patterns, trends, or cause-and-effect relationships.
• Communicating is the process of sharing information, ideas, or results with others through various forms of expression.
• Designing involves planning and creating solutions or models to address specific problems or challenges.

Hence, it can be concluded that option 2 is the correct answer.

Inquiry-oriented pedagogy is a teaching approach that emphasizes the importance of students actively engaging in the learning process through questioning, problem-solving, and investigation. 

Key PointsFrom the point of view of inquiry-oriented pedagogy, the strategy is appropriate because a conceptual framework was laid out right in the beginning. Here's why this approach aligns with inquiry-oriented pedagogy:

• Provides a Foundation: The teacher starts by defining photosynthesis and listing the essential factors (sunlight, water, air). This creates a basic understanding for students before they delve into the investigation.
• Encourages Active Exploration: The group project allows students to verify the importance of each factor through experimentation. This hands-on approach promotes active learning and discovery, which are core principles of inquiry-based learning.

Therefore, the correct answer is 'the strategy is appropriate because conceptual framework was laid out right in the beginning'.

Hint

• Option 2): While understanding the chemical reaction can be part of a more in-depth exploration, it's not crucial for a preliminary investigation of the conditions needed for photosynthesis at a class 8 level. The focus here is on observing the impact of different factors.
• Option 3): Group projects can be very valuable in inquiry-oriented learning. They encourage collaboration, communication, and shared learning. Individual activities can also work, but the choice depends on the specific learning objectives and the type of investigation.
• Option 4): This option presents a mischaracterization of the strategy.  While providing a framework offers some structure, it allows room for exploration.  The group project actively engages students in investigating the factors, not simply following a set of pre-determined instructions.

In an experiment, the dependent variable is the one that is measured or observed to determine the effect of the independent variable.

Key Points

• In this case, the students are investigating the effect of the length of the pendulum on its time period.
• The time period of the pendulum is the variable that will be measured or observed to see how it changes with different lengths of the pendulum.
• The independent variable, on the other hand, is the factor that is intentionally varied or manipulated by the experimenter.
• In this experiment, the independent variable is the length of the pendulum. The students are instructed to vary the length while keeping other factors
• constant.
• So, in this experiment, the length of the pendulum is the independent variable, and the time period of the pendulum is the dependent variable.
• The students are exploring how changes in the length of the pendulum affect its time period, which makes the time period the variable that depends on the length of the pendulum.

Hence, it can be concluded that option 3 is the correct answer.

When a species produces a large number of offspring, there is often not enough food, water, shelter, or other necessary resources to support all individuals.

Key Points

• This creates competition among the members of the species for these limited resources.

Only a fraction of the offspring will be able to survive and reproduce, while others will struggle and potentially perish.

• The struggle for existence can take various forms, such as competition for food, territorial disputes, or conflicts over mating opportunities.
• Individuals that are better adapted to their environment or possess advantageous traits have a higher chance of obtaining resources and surviving to reproductive age.
• This process of natural selection, where individuals with favourable traits are more likely to survive and pass on their genes, leads to the gradual evolution and adaptation of a species over time.

Hence, it can be concluded that option 2 is the correct answer.

In a science class, the primary focus is on fostering a collaborative and cooperative learning environment rather than promoting competition among students.

Key Points

• Science is a field that often requires teamwork, sharing of ideas, and collective problem-solving.
• Group activities are designed to encourage students to work together, communicate effectively, and learn from one another's perspectives and experiences.
• By collaborating in group activities, students can benefit from the diverse knowledge, skills, and viewpoints of their peers.
• They can engage in discussions, share ideas, conduct experiments together, and collectively analyze and interpret the results.
• This cooperative approach allows students to develop critical thinking skills, enhance their understanding of scientific concepts, and build strong interpersonal skills.
• Promoting collaboration over competition in science class activities fosters a supportive and inclusive learning environment where students feel encouraged to contribute, ask questions, and explore scientific phenomena together.

Hence, it can be concluded that To encourage students to compete with each other is NOT an objective of organising group activities in a science class.

In the paragraph, it is mentioned that Charles Darwin conducted studies during his voyage and later conducted various experiments upon returning to England. This indicates that Darwin engaged in scientific activities and research. Additionally, the paragraph mentions that Darwin would have been enlightened by Mendel's experiments if they had known about each other's work.

 Key Points

• This implies that scientists sharing their work and discoveries can be beneficial, as it allows for the exchange of knowledge, ideas, and insights.
• Collaboration and the sharing of work among scientists are fundamental aspects of the scientific process.
• Scientists often publish their findings, present them at conferences, and engage in discussions with their peers to contribute to the collective knowledge and advancement of their field.
• This collaborative approach fosters a broader understanding of scientific phenomena, promotes critical evaluation of research, and encourages further investigation and experimentation.

Hence, it can be concluded that option 2 is the correct answer.

This method encourages students to develop their observational skills, critical thinking, and scientific curiosity.

Key Points

• It also allows them to make connections between their observations and the concepts they are learning in the classroom.
• By recording and discussing their observations as a class, students can share their findings, compare notes, ask questions, and deepen their understanding of the topic through peer interaction and teacher guidance.
• By actively engaging with the subject matter, students can have a more memorable and meaningful learning experience.
• They can develop a firsthand understanding of how the moon's appearance changes and how constellations appear to move across the night sky.
• This approach promotes scientific inquiry, encourages students to think like scientists, and fosters a sense of wonder and appreciation for the natural world.

Hence, it can be concluded that option 3 is the correct answer.

It reflects a deeper level of engagement and interest in science beyond the foundational knowledge and skills.

Key Points

• It indicates that the student is not only familiar with the core concepts but also actively seeks information and stays updated on the latest developments in the field.
• Demonstrating an awareness of contemporary research trends suggests that the student has a genuine curiosity and interest in scientific advancements.
• They may engage in additional reading, follow scientific news, explore scientific journals, or participate in discussions related to ongoing research.
• This level of involvement indicates a passion for science and a desire to stay informed about current breakthroughs and discoveries.

 Hence, it can be concluded that Demonstrating an awareness of contemporary research trends can be a suitable indicator for assessing students' interest in science .

By posing a problem at the start of the laboratory work, the teacher sets the stage for inquiry and investigation.

Key Points

• The problem can be a real-world scenario, a scientific question, or a challenge that requires students to apply their knowledge and skills in a practical setting.
• This approach stimulates students' curiosity and prompts them to think critically and creatively.
• When students are presented with a problem, it activates their prior knowledge and encourages them to formulate hypotheses or potential solutions.
• They are motivated to design experiments, gather data, conduct observations, and carry out investigations to explore and seek answers to the problem at hand.
• This process engages students in active learning and provides them with an opportunity to develop and refine their scientific inquiry skills.

Hence, it can be concluded that option 3 is the correct answer.