Preparing for your exams is easier when you revise concepts and practice them with quality questions. This page offers Class 8 Science Chapter 9 MCQs based on the latest CBSE Board Class 8 Science Curiosity textbook. The questions are designed to help you strengthen conceptual understanding, identify weak areas, and gain confidence before school tests and annual examinations.
Whether you're revising this chapter for the first time or doing a final round of practice, these multiple choice questions with detailed explanations will help you understand the logic behind each answer instead of relying on memorization. This approach improves accuracy and makes revision more effective.
If you're looking for more chapter-wise practice, explore our complete collection of Class 8 MCQs and Class 8 Science MCQs, where you'll find subject-wise questions prepared according to the latest CBSE Board curriculum. You can also visit our comprehensive MCQs hub to practice questions from different chapters and subjects in one place.
Practice Class 8 Science Chapter 9 MCQs
Start with the questions before reading the revision notes. Solving them on your own first will help you identify which concepts you already understand and which ones need another look.
Q. Which of the following best describes a solution?
A. A mixture in which particles settle after some time
B. A homogeneous mixture formed when a solute dissolves in a solvent
C. A mixture of only two solids
D. A substance made only of water
Answer: B
Explanation: A solution is a homogeneous mixture in which the solute is evenly distributed throughout the solvent. The components cannot be distinguished by the naked eye.
Q. Sugar disappears after being stirred in a glass of water. In this process, sugar acts as the:
A. Solvent
B. Solution
C. Solute
D. Suspension
Answer: C
Explanation: The substance that gets dissolved is called the solute. Here, sugar dissolves in water, so it is the solute.
Q. Which statement correctly explains why water is called the universal solvent?
A. It dissolves every substance without exception.
B. It can dissolve a large variety of substances compared to most liquids.
C. It is available in every part of the Earth.
D. It changes every solid into a liquid.
Answer: B
Explanation: Water cannot dissolve everything, but it dissolves more substances than most other liquids. This is why it is known as the universal solvent.
Q. A student keeps adding salt to water until some salt remains undissolved at the bottom. The solution has become:
A. Dilute
B. Unsaturated
C. Saturated
D. Concentrated only
Answer: C
Explanation: A saturated solution cannot dissolve any more solute at the same temperature. Excess salt remains undissolved.
Q. Which situation represents an unsaturated solution?
A. Extra sugar settles at the bottom of the cup.
B. More sugar can still dissolve in the water.
C. The solution contains only water.
D. The solvent has completely evaporated.
Answer: B
Explanation: An unsaturated solution still has the capacity to dissolve additional solute under the same conditions.
Q. A spoonful of sugar dissolves faster in warm water than in cold water because:
A. Warm water has less mass.
B. Molecules move faster at a higher temperature.
C. Sugar becomes lighter in warm water.
D. Warm water changes into a different liquid.
Answer: B
Explanation: Higher temperature increases the movement of water molecules, helping the sugar particles spread and dissolve more quickly.
Q. Which quantity is calculated using the formula Mass ÷ Volume?
A. Weight
B. Density
C. Pressure
D. Solubility
Answer: B
Explanation: Density tells us how much mass is packed into a given volume. It is calculated by dividing mass by volume.
Q. A wooden block floats on water mainly because:
A. It has no mass.
B. Its density is lower than the density of water.
C. Water pushes it upward continuously.
D. It contains only air.
Answer: B
Explanation: Objects float when their density is lower than that of the liquid in which they are placed.
Q. Which instrument is commonly used to measure the volume of a liquid accurately?
A. Spring balance
B. Thermometer
C. Measuring cylinder
D. Stopwatch
Answer: C
Explanation: A measuring cylinder is specially designed for measuring liquid volume. The reading should be taken at the bottom of the meniscus.
Q. A peeled orange sinks in water because:
A. Its colour changes after peeling.
B. The peel absorbs all the water.
C. Removing the peel removes trapped air, increasing its overall density.
D. The fruit becomes heavier after peeling.
Answer: C
Explanation: The peel contains tiny air pockets that help the orange float. Once the peel is removed, its average density becomes greater than that of water, causing it to sink.
Q. Assertion (A): Most solid substances dissolve faster in hot water than in cold water.
Reason (R): Heating increases the movement of water molecules.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.
Answer: A
Explanation: Heating increases the kinetic energy of water molecules. They move faster and interact more frequently with solute particles, making most solids dissolve more quickly.
Q. A student mixes one teaspoon of salt in 100 mL of water. After all the salt dissolves, the mixture formed is called a:
A. Suspension
B. Solution
C. Compound
D. Colloid
Answer: B
Explanation: When a solute dissolves completely and forms a uniform mixture with the solvent, the resulting mixture is called a solution.
Q. Which observation shows that a solution is homogeneous?
A. Different layers can be seen.
B. The dissolved particles are evenly distributed throughout the mixture.
C. Large particles settle at the bottom after some time.
D. The mixture can be separated using a sieve.
Answer: B
Explanation: In a homogeneous solution, the solute is uniformly distributed, making the mixture appear the same throughout.
Q. A student wants to dissolve more sugar in a cup of water that has already become saturated at room temperature. What should the student do first?
A. Add sand to the solution.
B. Heat the solution.
C. Remove half of the water.
D. Stir without changing the temperature.
Answer: B
Explanation: Heating generally increases the solubility of most solid solutes, allowing more sugar to dissolve.
Q. A metal cube has a mass of 180 g and a volume of 20 cm³. What is its density?
A. 9 g/cm³
B. 18 g/cm³
C. 160 g/cm³
D. 200 g/cm³
Answer: A
Explanation: Density = Mass ÷ Volume = 180 ÷ 20 = 9 g/cm³.
Q. Which of the following is most likely to dissolve completely in water?
A. Cooking oil
B. Sand
C. Sugar
D. Chalk powder
Answer: C
Explanation: Sugar is soluble in water and forms a clear solution, whereas oil, sand, and chalk powder do not dissolve completely.
Q. While reading the volume of water in a measuring cylinder, a student should look at:
A. The top edge of the cylinder.
B. The upper surface of the liquid from above.
C. The bottom of the meniscus at eye level.
D. Any point where the liquid touches the cylinder.
Answer: C
Explanation: To avoid measurement errors, the liquid level should always be read at the bottom of the meniscus while keeping the eye level with the liquid.
Q. Case-Based Question
Riya prepared two glasses of water. She added one spoon of sugar to the first glass and one spoon of salt to the second. After stirring both, she observed that neither substance was visible.
What can Riya conclude from this observation?
A. Both sugar and salt disappeared permanently.
B. Both substances dissolved to form homogeneous solutions.
C. Water changed into a new substance.
D. Sugar and salt turned into gases.
Answer: B
Explanation: Sugar and salt dissolve in water, forming homogeneous solutions. The particles are still present but are evenly distributed throughout the water.
Q. Which statement about density is correct?
A. Density changes whenever the shape of an object changes.
B. Density depends only on the colour of the material.
C. Density is the mass present in a unit volume of a substance.
D. Density is always equal to the volume of an object.
Answer: C
Explanation: Density is an intrinsic property that relates the mass of a substance to the volume it occupies. Changing the shape does not change its density.
Q. A student accidentally drops a sealed plastic bottle filled with air into a bucket of water. The bottle floats because:
A. Air has no mass.
B. The average density of the bottle is less than that of water.
C. Plastic always floats regardless of its density.
D. Water becomes lighter when a bottle is placed in it.
Answer: B
Explanation: The air inside the bottle increases its volume without adding much mass, making the bottle's average density lower than that of water. Hence, it floats.
Q. Assertion (A): A peeled orange usually sinks in water.
Reason (R): Removing the peel removes tiny air pockets that help reduce the orange's overall density.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.
Answer: A
Explanation: The peel contains tiny trapped air pockets that make the orange less dense overall. After peeling, these air pockets are removed, increasing the orange's average density and causing it to sink.
Q. A student prepares two sugar solutions using the same amount of water. One solution contains 2 teaspoons of sugar, while the other contains 6 teaspoons. Which statement is correct?
A. Both solutions have the same concentration.
B. The second solution is more concentrated.
C. The first solution is saturated.
D. The second solution cannot be a solution.
Answer: B
Explanation: When the amount of solvent remains the same, adding more solute increases the concentration, provided all the solute dissolves.
Q. A liquid has a mass of 150 g and occupies 75 cm³. Its density is:
A. 0.5 g/cm³
B. 1 g/cm³
C. 2 g/cm³
D. 75 g/cm³
Answer: C
Explanation: Density = Mass ÷ Volume = 150 ÷ 75 = 2 g/cm³.
Q. Which of the following situations best demonstrates the effect of temperature on solubility?
A. Ice melting into water
B. Sugar dissolving more quickly in warm milk than in cold milk
C. Oil floating on water
D. Sand settling at the bottom of a beaker
Answer: B
Explanation: Increasing temperature generally increases the rate at which most solid solutes dissolve in liquids.
Q. Case-Based Question
During a science activity, Aarav noticed that fish are more active in a pond during winter than during very hot summer afternoons. His teacher explained that the amount of dissolved oxygen changes with temperature.
Which statement correctly explains this observation?
A. Oxygen dissolves better in warm water.
B. Oxygen dissolves better in cold water.
C. Oxygen cannot dissolve in water.
D. Temperature does not affect dissolved gases.
Answer: B
Explanation: Gases such as oxygen are more soluble in cold water. This provides aquatic animals with more dissolved oxygen during cooler conditions.
Q. Which pair correctly matches the term with its meaning?
A. Solvent - Substance that gets dissolved
B. Solute - Substance that dissolves another substance
C. Solution - Uniform mixture of solute and solvent
D. Density - Space occupied by an object
Answer: C
Explanation: A solution is a homogeneous mixture formed when a solute dissolves completely in a solvent. The other options incorrectly define the terms.
Q. A student changes the shape of a clay ball into a flat disc without adding or removing any clay. Which property remains unchanged?
A. Shape only
B. Density only
C. Volume only
D. Colour only
Answer: B
Explanation: Since the mass and volume of the clay remain the same, its density also remains unchanged, even though its shape changes.
Q. Which of the following observations indicates that no more solute can dissolve in a solution?
A. The solution becomes colourless.
B. The liquid starts boiling.
C. Some solute remains undissolved even after stirring.
D. The solution becomes heavier than water.
Answer: C
Explanation: When excess solute remains at the bottom despite stirring, the solution has reached its saturation point.
Q. A student wants to prepare a clear salt solution for an experiment. Which step is the most important?
A. Add large stones to the water.
B. Stir the salt thoroughly until it dissolves completely.
C. Freeze the water immediately after adding salt.
D. Pour the solution through a cloth before mixing.
Answer: B
Explanation: Proper stirring allows the salt particles to come into contact with the water, helping them dissolve and form a uniform solution.
Q. Competency-Based Question
Four identical containers hold equal volumes of different liquids. A metal ball sinks in Liquids P, Q, and R but floats in Liquid S.
What can you conclude about Liquid S?
A. It has the lowest density among the four liquids.
B. It has the highest density among the four liquids.
C. It contains no dissolved substances.
D. Its volume is greater than the other liquids.
Answer: B
Explanation: An object floats only when the liquid is denser than the object. Since the metal ball floats only in Liquid S, Liquid S must have the highest density among the four.
Class 8 Science Chapter 9 Overview
The Amazing World of Solutes, Solvents, and Solutions explains how different substances mix to form solutions and why some materials dissolve while others do not. The chapter also introduces important concepts like saturated and unsaturated solutions, solubility, mass, volume, density, and the relationship between floating and sinking.
Many of these ideas can be observed in everyday life. Sugar dissolving in water, salt mixing in soup, or an orange floating before peeling are simple examples that help explain scientific principles. Along with theory, students also learn the density formula and how temperature affects the dissolving process.
Quick Revision Notes
| Concept | Quick Revision |
|---|---|
| Solute | The substance that dissolves in another substance. |
| Solvent | The substance that dissolves the solute. Water is the most common solvent. |
| Solution | A homogeneous mixture formed when a solute dissolves completely in a solvent. |
| Universal Solvent | Water is called the universal solvent because it can dissolve many different substances. |
| Unsaturated Solution | A solution that can still dissolve more solute at the same temperature. |
| Saturated Solution | A solution that cannot dissolve any more solute at the given temperature. |
| Solubility | The maximum amount of solute that can dissolve in a fixed amount of solvent at a specific temperature. |
| Mass | The amount of matter present in an object. |
| Volume | The space occupied by an object or a liquid. |
| Density | The amount of mass present in a given volume. |
| Density Formula | Density = Mass ÷ Volume |
| Volume of a Cuboid | Length × Breadth × Height |
| Heating Effect | Most solid solutes dissolve faster and in larger amounts in warm water. |
| Gas Solubility | Gases like oxygen dissolve better in cold water than in hot water. |
| Floating Rule | An object floats if its density is lower than the density of the liquid. |
| Orange Experiment | An unpeeled orange floats because of trapped air in its peel. A peeled orange usually sinks because its density becomes greater than that of water. |
| Meniscus | While measuring liquids, always read the level at the bottom of the curved surface. |
Class 8 Science Chapter 9 MCQs Solving Tips
- A few simple habits can help you answer Chapter 9 MCQs more accurately.
- Understand the difference between solute, solvent, and solution instead of memorizing their definitions.
- Revise the density formula and practice basic numerical questions.
- Read every option carefully before selecting an answer.
- Do not confuse saturated and unsaturated solutions.
- Remember that heating usually increases the solubility of solids, but gases behave differently.
- Use everyday examples like sugar in water, salt solution, and the floating orange to connect concepts with real life.
- While solving calculation-based questions, always check the units before choosing the final answer.
