✅ True or False (10 Questions)

Chapter 9: Solutes, Solvents, and Solutions

(CBSE Class 8 Standard | Good Quality)

1. A uniform mixture of salt and water is called a solution.
   True hecu109

2. In a solution, the solute is present in a larger amount than the solvent.
   False
   (The solute is usually present in a smaller amount, and the solvent in a larger amount.) hecu109

3. Chalk powder mixed with water forms a uniform mixture.
   False
   (Chalk powder forms a non-uniform mixture.) hecu109

4. Sugar dissolved in water forms a non-uniform mixture.
   False
   (It forms a uniform solution.) hecu109

5. A saturated solution cannot dissolve any more solute at a given temperature.
   True hecu109

6. An unsaturated solution can dissolve more solute at the same temperature.
   True hecu109

7. Solubility is the maximum amount of solute that can dissolve in a fixed amount of solvent at a given temperature.
   True hecu109

8. The solubility of most solids decreases when temperature increases.
   False
   (For most solids, solubility increases with rise in temperature.) hecu109

9. Oxygen dissolves in water and helps aquatic animals survive.
   True hecu109

10. Density is defined as mass per unit volume of a substance.
    True

✅ Fill in the Blanks (10 Questions)

Chapter 9: Solutes, Solvents, and Solutions

(CBSE Class 8 Standard | Good Quality)

1. A homogeneous mixture of solute and solvent is called a __________.
   Answer: solution hecu109

2. The substance that dissolves in a solution is called the __________.
   Answer: solute hecu109

3. The substance in which the solute dissolves is called the __________.
   Answer: solvent hecu109

4. A mixture that is not uniform throughout is called a __________ mixture.
   Answer: non-uniform hecu109

5. A solution that cannot dissolve more solute at a given temperature is called a __________ solution.
   Answer: saturated hecu109

6. A solution that can still dissolve more solute is called an __________ solution.
   Answer: unsaturated hecu109

7. The maximum amount of solute that can dissolve in a given amount of solvent is called __________.
   Answer: solubility hecu109

8. The solubility of most solids generally __________ with increase in temperature.
   Answer: increases hecu109

9. The amount of dissolved oxygen in water is important for the survival of __________ animals.
   Answer: aquatic hecu109

10. Density is calculated using the formula: Density = Mass ÷ __________.
    Answer: volume

✅ Multiple Choice Questions (15 MCQs)

Chapter 9: Solutes, Solvents, and Solutions

(CBSE Class 8 Standard | Good Quality)

1. A solution is a:

A. Non-uniform mixture
B. Homogeneous mixture
C. Solid substance
D. Pure element
✅ Answer: B hecu109

2. In salt solution, salt is the:

A. Solvent
B. Solute
C. Mixture
D. Residue
✅ Answer: B hecu109

3. The substance present in larger amount in a solution is called:

A. Solute
B. Solvent
C. Density
D. Suspension
✅ Answer: B hecu109

4. Which of the following is a non-uniform mixture?

A. Sugar in water
B. Salt in water
C. Chalk powder in water
D. ORS solution
✅ Answer: C hecu109

5. A saturated solution means:

A. No solute is dissolved
B. It can dissolve more solute
C. It cannot dissolve more solute at that temperature
D. It contains only solvent
✅ Answer: C hecu109

6. An unsaturated solution:

A. Contains no solvent
B. Can dissolve more solute
C. Is always solid
D. Has maximum solute
✅ Answer: B hecu109

7. Solubility depends mainly on:

A. Colour of solute
B. Temperature
C. Shape of container
D. Smell of solvent
✅ Answer: B hecu109

8. The solubility of most solids in water:

A. Decreases with temperature
B. Increases with temperature
C. Remains constant always
D. Becomes zero
✅ Answer: B hecu109

9. Aquatic animals survive because water contains dissolved:

A. Nitrogen
B. Carbon dioxide
C. Oxygen
D. Hydrogen
✅ Answer: C hecu109

10. The formula for density is:

A. Volume ÷ Mass
B. Mass × Volume
C. Mass ÷ Volume
D. Mass + Volume
✅ Answer: C hecu109

11. If a substance has high density, it will:

A. Float easily
B. Sink in water
C. Become gas
D. Dissolve completely
✅ Answer: B hecu109

12. ORS is an example of:

A. Suspension
B. Non-uniform mixture
C. Solution
D. Pure substance
✅ Answer: C hecu109

13. The curved surface of liquid in a measuring cylinder is called:

A. Focus
B. Meniscus
C. Density
D. Solute
✅ Answer: B hecu109

14. Volume of an irregular solid is measured using:

A. Thermometer
B. Displacement method
C. Barometer
D. Compass
✅ Answer: B hecu109

15. Which of the following increases solubility of a solid?

A. Cooling the solution
B. Heating the solution
C. Removing solvent
D. Adding oil
✅ Answer: B

✅ Assertion–Reason Questions (10)

Chapter 9: Solutes, Solvents, and Solutions

(CBSE Class 8 Standard | Good Quality)

Directions: Choose the correct option:

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

1.

Assertion (A): A solution is a homogeneous mixture.
Reason (R): In a solution, the solute is uniformly distributed throughout the solvent.
✅ Answer: A hecu109

2.

Assertion (A): Salt water is an example of a solution.
Reason (R): Salt dissolves completely in water forming a uniform mixture.
✅ Answer: A hecu109

3.

Assertion (A): Chalk powder mixed with water forms a solution.
Reason (R): Chalk powder does not dissolve and forms a non-uniform mixture.
✅ Answer: D hecu109

4.

Assertion (A): A saturated solution cannot dissolve more solute at a given temperature.
Reason (R): It already contains the maximum amount of dissolved solute.
✅ Answer: A hecu109

5.

Assertion (A): An unsaturated solution can dissolve more solute.
Reason (R): It has not reached its maximum solubility limit.
✅ Answer: A hecu109

6.

Assertion (A): Solubility of most solids increases with rise in temperature.
Reason (R): Higher temperature provides more energy for solute particles to dissolve.
✅ Answer: A hecu109

7.

Assertion (A): Solubility of gases in water decreases when temperature increases.
Reason (R): Warm water holds less dissolved gas than cold water.
✅ Answer: A hecu109

8.

Assertion (A): Oxygen dissolved in water is essential for aquatic life.
Reason (R): Aquatic animals use dissolved oxygen for respiration.
✅ Answer: A hecu109

9.

Assertion (A): Density is defined as mass per unit volume.
Reason (R): Density helps determine whether an object will float or sink.
✅ Answer: B hecu109

10.

Assertion (A): Volume of an irregular object can be measured using displacement method.
Reason (R): The object displaces an equal volume of water when submerged.
✅ Answer: A

✅ Very Short Answer Questions (10 Questions)

Chapter 9: Solutes, Solvents, and Solutions

(2 Marks Each | CBSE Class 8 Standard | Good Quality)

1. What is a solution?

Answer:
A solution is a homogeneous mixture in which a solute is uniformly dissolved in a solvent. hecu109

2. Define solute with an example.

Answer:
A solute is the substance that dissolves in a solvent. Example: Salt in salt water. hecu109

3. Define solvent with an example.

Answer:
A solvent is the substance in which the solute dissolves. Example: Water in sugar solution. hecu109

4. What is a saturated solution?

Answer:
A saturated solution is one that cannot dissolve any more solute at a given temperature. hecu109

5. What is an unsaturated solution?

Answer:
An unsaturated solution is one that can still dissolve more solute at the same temperature. hecu109

6. Define solubility.

Answer:
Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature. hecu109

7. Why do aquatic animals need dissolved oxygen?

Answer:
Aquatic animals use dissolved oxygen present in water for respiration and survival. hecu109

8. What is density?

Answer:
Density is the mass per unit volume of a substance. It is calculated as Density = Mass ÷ Volume. hecu109

9. What is the meniscus of a liquid?

Answer:
The meniscus is the curved surface of a liquid in a measuring cylinder, used to read volume correctly. hecu109

10. How is the volume of an irregular solid measured?

Answer:
The volume of an irregular solid is measured by the displacement method using water in a measuring cylinder

✅ Short Answer Questions (10 Questions)

Chapter 9: Solutes, Solvents, and Solutions

(3 Marks Each | CBSE Class 8 Standard | Good Quality)

1. Differentiate between solute and solvent with examples.

Answer:
A solute is the substance that dissolves in a solution, such as salt or sugar. A solvent is the substance in which the solute dissolves, such as water. For example, in salt solution, salt is the solute and water is the solvent. hecu109

2. Explain the difference between saturated and unsaturated solutions.

Answer:
A saturated solution contains the maximum amount of solute that can dissolve at a given temperature, so no more solute can be added. An unsaturated solution contains less solute and can dissolve more solute at the same temperature. hecu109

3. What is solubility? How does temperature affect it?

Answer:
Solubility is the maximum amount of solute that can dissolve in a fixed amount of solvent at a given temperature. For most solids, solubility increases with rise in temperature. hecu109

4. Why does sugar dissolve faster in hot water than in cold water?

Answer:
In hot water, molecules move faster and have more energy. This helps the sugar particles mix and dissolve quickly, increasing the rate of dissolution. hecu109

5. Explain why solubility of gases decreases with increase in temperature.

Answer:
When water is heated, gas molecules gain energy and escape from the liquid. Therefore, warm water holds less dissolved gases compared to cold water. hecu109

6. What is the importance of dissolved oxygen in water?

Answer:
Dissolved oxygen is necessary for aquatic animals and plants. Fish and other organisms breathe using oxygen dissolved in water, making it essential for aquatic life. hecu109

7. Define density and explain its role in floating and sinking.

Answer:
Density is mass per unit volume. If an object has a density greater than water, it sinks. If its density is less than water, it floats. Thus, density determines floating or sinking. hecu109

8. Explain the displacement method of measuring volume.

Answer:
In the displacement method, an irregular solid is immersed in water in a measuring cylinder. The rise in water level gives the volume of the object, as it displaces an equal volume of water. hecu109

9. What precautions should be taken while reading volume in a measuring cylinder?

Answer:
The measuring cylinder should be placed on a flat surface. The reading should be taken at eye level from the lower meniscus to avoid errors. hecu109

10. Give two examples each of uniform and non-uniform mixtures.

Answer:
Uniform mixtures: Salt solution, sugar solution.
Non-uniform mixtures: Chalk in water, sand in water.

✅ Case-Based Questions (4 Cases)

Chapter 9: Solutes, Solvents, and Solutions

(4 Marks Each | Sub-questions: 1 + 1 + 2 Marks)
CBSE Competency-Based Standard

Case 1: ORS Solution

Oral Rehydration Solution (ORS) is prepared by dissolving salt and sugar in water. It is commonly used to prevent dehydration during diarrhoea. ORS forms a uniform mixture.

Questions:

Q1. (1 Mark) What type of mixture is ORS?
Answer: A solution (uniform mixture). hecu109

Q2. (1 Mark) In ORS, water acts as the ________.
Answer: Solvent hecu109

Q3. (2 Marks) Why is ORS called a solution?
Answer:
ORS is called a solution because salt and sugar dissolve completely in water, forming a homogeneous mixture. hecu109

Case 2: Saturated and Unsaturated Solutions

A student adds sugar to a glass of water. After some time, no more sugar dissolves and sugar crystals settle at the bottom.

Questions:

Q1. (1 Mark) What is this solution called?
Answer: Saturated solution hecu109

Q2. (1 Mark) What happens if more sugar is added?
Answer: It will not dissolve further. hecu109

Q3. (2 Marks) Why does sugar remain undissolved at the bottom?
Answer:
Because the solution has reached its maximum solubility limit at that temperature and cannot dissolve more solute. hecu109

Case 3: Solubility of Gases

Cold water contains more dissolved oxygen than warm water. This is why fish survive better in cooler water bodies.

Questions:

Q1. (1 Mark) Which gas is dissolved in water for aquatic life?
Answer: Oxygen hecu109

Q2. (1 Mark) Does solubility of gases increase or decrease with temperature?
Answer: Decreases hecu109

Q3. (2 Marks) Why does warm water contain less dissolved oxygen?
Answer:
Because gas molecules escape more easily from warm water, reducing the amount of dissolved oxygen. hecu109

Case 4: Density and Floating

A piece of wood floats on water, while a stone sinks. This happens due to differences in density.

Questions:

Q1. (1 Mark) What is density?
Answer: Mass per unit volume. hecu109

Q2. (1 Mark) Why does wood float on water?
Answer: Because its density is less than water. hecu109

Q3. (2 Marks) Why does a stone sink in water?
Answer:
Because the density of stone is greater than the density of water, so it sinks.

✅ Long Answer Questions (5 Questions)

Chapter 9: Solutes, Solvents, and Solutions

(5 Marks Each | CBSE Class 8 Standard | High Quality Answers)

1. Explain solute, solvent, and solution with suitable examples.

Answer:
A solution is a homogeneous mixture formed when one substance dissolves in another.

• Solute: The substance that dissolves. Example: Salt or sugar.
• Solvent: The substance in which the solute dissolves. Example: Water.
• Solution: The uniform mixture formed after dissolving. Example: Salt solution.

For example, when salt is mixed with water, salt is the solute, water is the solvent, and salt water is the solution. hecu109

2. Differentiate between saturated and unsaturated solutions.

Answer:
Solutions can be classified based on how much solute they contain:

Saturated Solution

• Contains maximum solute that can dissolve at a given temperature.
• Cannot dissolve more solute.

Unsaturated Solution

• Contains less solute than the maximum limit.
• Can dissolve more solute at the same temperature.

Example: If sugar continues to dissolve in water, it is unsaturated. If sugar stops dissolving and settles at the bottom, it is saturated. hecu109

3. What is solubility? Discuss the effect of temperature on solubility of solids and gases.

Answer:
Solubility is the maximum amount of solute that can dissolve in a fixed amount of solvent at a given temperature.

Effect on Solids:

• Solubility of most solids increases with rise in temperature.
  Example: More sugar dissolves in hot water than cold water.

Effect on Gases:

• Solubility of gases decreases with rise in temperature.
  Example: Warm water contains less dissolved oxygen than cold water.

Thus, temperature affects solubility differently for solids and gases. hecu109

4. Explain density and its role in floating and sinking.

Answer:
Density is defined as the mass per unit volume of a substance.

Formula:
Density = Mass ÷ Volume

Floating and Sinking:

• If an object has density less than water, it floats.
  Example: Wood floats.
• If an object has density greater than water, it sinks.
  Example: Stone sinks.

Thus, density helps us understand why some objects float while others sink. hecu109

5. Describe how the volume of an irregular solid is measured using displacement method.

Answer:
The volume of an irregular object cannot be measured directly with a ruler. So, the displacement method is used.

Steps:

1. Take water in a measuring cylinder and note the initial level.
2. Immerse the irregular solid completely in water.
3. Note the final water level.
4. The difference in water level gives the volume of the object.

This method works because the object displaces an equal volume of water when submerged.