Chapter: 5 – Exploring Mixtures and Their Separation
Maximum Marks: 50
Suggested Time: 1 Hour 30 Minutes

This Class 9 Science Exploration Chapter 5 Sample Paper 1 is designed to help students practise important concepts from “Exploring Mixtures and Their Separation.” The paper covers pure substances and mixtures, homogeneous and heterogeneous mixtures, solutions, solute and solvent, concentration, suspensions, colloids, filtration, evaporation, distillation, chromatography, centrifugation, and separation of mixtures in daily life. Complete solutions are provided at the end.

Sample Paper 1

General Instructions

1. All questions are compulsory.
2. Read each question carefully before answering.
3. Write answers using appropriate scientific terminology.
4. Show all steps in numerical questions.
5. Draw neat and labelled diagrams wherever required.
6. Use suitable examples to support your answers.

Section A — Objective Questions

10 × 1 = 10 Marks

Q1. Which of the following is a mixture?

a) Oxygen
b) Copper
c) Air
d) Distilled water

Q2. A mixture having a uniform composition throughout is called:

a) Heterogeneous mixture
b) Homogeneous mixture
c) Suspension
d) Colloid

Q3. In a salt solution, salt is the:

a) Solvent
b) Solute
c) Residue
d) Filtrate

Q4. Which method is most suitable for separating sand from water?

a) Filtration
b) Distillation
c) Chromatography
d) Sublimation

Q5. Which method can be used to obtain salt from seawater?

a) Filtration only
b) Evaporation
c) Decantation only
d) Chromatography

Q6. Which of the following is an example of a suspension?

a) Salt solution
b) Sugar solution
c) Muddy water
d) Air

Q7. Which type of mixture shows the scattering of light by its dispersed particles?

a) True solution
b) Colloid
c) Pure substance
d) Element

Q8. Which separation technique is commonly used to separate different coloured substances present in ink?

a) Filtration
b) Chromatography
c) Sedimentation
d) Decantation

Q9. The substance that dissolves another substance to form a solution is called:

a) Solute
b) Solvent
c) Residue
d) Suspension

Q10. Which method is particularly useful for separating cream from milk?

a) Centrifugation
b) Filtration
c) Evaporation
d) Crystallisation

Section B — Very Short Answer Questions

5 × 2 = 10 Marks

Q11. Define a mixture. Give one example of a mixture found in your surroundings.

Q12. Differentiate between a homogeneous mixture and a heterogeneous mixture with one example of each.

Q13. What are solute and solvent? Identify them in a sugar-water solution.

Q14. State any two differences between a solution and a suspension.

Q15. Why is filtration not suitable for separating dissolved salt from water?

Section C — Short Answer Questions

4 × 3 = 12 Marks

Q16. Explain the terms solution, solute and solvent using the example of a copper sulphate solution.

Q17. What is a colloid? State two properties that distinguish a colloid from a true solution.

Q18. Explain how you would separate a mixture containing iron filings and sand. Mention the principle involved.

Q19. A mixture contains water, common salt and insoluble sand. Describe a suitable sequence of methods to separate all three components.

Section D — Application-Based Questions

2 × 4 = 8 Marks

Q20. A student is given a mixture of small pieces of chalk and water.

Answer the following:

a) What type of mixture is formed?
b) Which separation method should the student use first?
c) What happens to the chalk particles during this process?
d) What will be collected as the filtrate?

Q21. A science student puts a small quantity of black ink on a strip of suitable paper and places the lower end of the strip in a suitable solvent. After some time, several coloured spots appear at different heights.

Answer the following:

a) Name the separation technique.
b) What does the experiment show about black ink?
c) Why do the coloured substances move different distances?
d) Give one practical use of this technique.

Section E — Long Answer and Numerical Questions

2 × 5 = 10 Marks

Q22. Explain the difference between a true solution, a suspension and a colloid. Compare them on the basis of particle size, visibility of particles, settling and filtration.

Q23. A student prepares a solution by dissolving 20 g of common salt in 180 g of water.

Calculate:

a) The mass of the solution.
b) The mass percentage of salt in the solution.

Also write the formula used for calculating mass percentage.

SOLUTIONS

Section A — Answers

Q1. c) Air

Q2. b) Homogeneous mixture

Q3. b) Solute

Q4. a) Filtration

Q5. b) Evaporation

Q6. c) Muddy water

Q7. b) Colloid

Q8. b) Chromatography

Q9. b) Solvent

Q10. a) Centrifugation

Section B — Solutions

Q11. Mixture

A mixture is a combination of two or more substances in which the substances retain their individual properties and can generally be separated by physical methods.

Example: Air, soil, lemonade or salt water.

Q12. Homogeneous and Heterogeneous Mixtures

A homogeneous mixture has a uniform composition throughout.

Example: Salt dissolved in water.

A heterogeneous mixture does not have a uniform composition throughout.

Example: Sand mixed with water.

Q13. Solute and Solvent

The solute is the substance that gets dissolved.

The solvent is the substance that dissolves the solute.

In a sugar-water solution:

• Sugar = solute
• Water = solvent

Q14. Solution and Suspension

For example, salt water is a solution, while muddy water is a suspension.

Q15. Why Cannot Filtration Separate Dissolved Salt?

In salt water, the salt particles are dissolved at the molecular or ionic level and are too small to be retained by ordinary filter paper.

Therefore, the salt passes through the filter along with water.

To recover the salt, evaporation or crystallisation can be used.

Section C — Solutions

Q16. Solution, Solute and Solvent

Suppose copper sulphate is dissolved in water.

The resulting mixture is a solution.

• Copper sulphate is the solute because it dissolves in water.
• Water is the solvent because it dissolves the copper sulphate.
• The uniform mixture formed is called a copper sulphate solution.

Thus:Solute + Solvent = Solution​

Q17. Colloid

A colloid is a mixture in which very small particles of one substance are dispersed throughout another substance.

Examples include milk, fog and starch solution.

Two important properties are:

1. Colloidal particles are small enough not to settle easily under gravity.
2. Colloids can scatter a beam of light, producing the Tyndall effect.

Unlike a true solution, a colloid is not completely transparent to a beam of light.

Q18. Separating Iron Filings and Sand

A mixture of iron filings and sand can be separated using a magnet.

Method:

1. Spread the mixture on a sheet or suitable surface.
2. Move a magnet over the mixture.
3. The iron filings are attracted to the magnet.
4. The sand remains behind.

Principle:

The separation is based on the magnetic property of iron.

Therefore, magnetic separation can be used to separate the iron filings from the sand.

Q19. Separating Salt, Water and Sand

The mixture contains:

• Water
• Dissolved common salt
• Insoluble sand

A suitable sequence is:

Step 1 — Filtration

Pass the mixture through filter paper.

• Sand remains as the residue.
• Salt solution passes through as the filtrate.

Step 2 — Evaporation or Crystallisation

Heat the salt solution carefully.

Water is removed through evaporation, leaving common salt behind.

If obtaining purer salt crystals is desired, crystallisation can be used.

Thus, the three components can be separated using:Filtration→Evaporation/Crystallisation​

Section D — Solutions

Q20. Chalk and Water

a) Chalk and water form a suspension because the insoluble chalk particles are dispersed in water.

b) The suitable method is filtration.

c) The chalk particles are retained by the filter paper as the residue.

d) Water passes through the filter paper and is collected as the filtrate.

Therefore:

• Residue = chalk
• Filtrate = water

Q21. Separation of Ink Components

a) The technique is chromatography.

b) The experiment shows that black ink is a mixture of different coloured substances.

c) Different substances travel different distances because they have different interactions with the paper and the solvent. Consequently, they move at different rates.

d) Chromatography can be used to:

• separate components of inks and dyes;
• identify substances;
• analyse mixtures in laboratories.

Section E — Solutions

Q22. True Solution, Suspension and Colloid

A true solution, suspension and colloid differ mainly in their particle size and behaviour.

True Solution

A true solution is homogeneous. Its dissolved particles are extremely small and do not settle on standing.

Example: Salt solution.

Colloid

A colloid contains intermediate-sized dispersed particles. These particles generally remain dispersed and show the Tyndall effect.

Example: Milk.

Suspension

A suspension contains relatively large insoluble particles. These particles can settle when the mixture is left undisturbed and can generally be separated by filtration.

Example: Muddy water.

Q23. Mass Percentage of Salt

Given:

Mass of salt = 20 g

Mass of water = 180 g

a) Mass of Solution

Mass of solution=Mass of solute+Mass of solvent=20+180200 g​

b) Mass Percentage

The formula is:Mass Percentage=Mass of solutionMass of solute​×100

Substituting the values:Mass Percentage=20020​×100=10%10%​

Final Answers

Mass of solution = 200 g

Mass percentage of salt = 10%