Science Exploration Notes Class 9 English Medium 2026-27

Science Exploration Chapter 5. Exploring Mixtures and their Separation

CBSE Notes New Syllabus: Class 9

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Chapter 5. Exploring Mixtures and their Separation

This assignment is based on the complete chapter and follows the latest CBSE competency-based assessment pattern. It includes objective, descriptive, application-based, case-study and HOTS questions to strengthen conceptual understanding and scientific reasoning.

Chapter Assignment

1. One Word Answer

1. A physical combination of two or more substances.
2. A substance made up of only one kind of particles.
3. The substance that gets dissolved in a solution.
4. The substance that dissolves the solute.
5. A homogeneous mixture of solute and solvent.
6. The maximum amount of solute that dissolves in a solvent.
7. The process used to separate insoluble solids from liquids.
8. The process used to obtain pure crystals from a solution.
9. The apparatus used to separate immiscible liquids.
10. The phenomenon shown by colloidal particles when light passes through them.

2. Fill in the Blanks

1. A mixture has a __________ composition.
2. A solution is a __________ mixture.
3. Salt is the __________ in a salt solution.
4. The liquid that dissolves a solute is called the __________.
5. A solution that cannot dissolve more solute is called a __________ solution.
6. Filtration separates __________ solids from liquids.
7. Fractional distillation is used to separate __________ liquids.
8. Particles in a suspension __________ on standing.
9. Milk is an example of a __________.
10. The Tyndall effect is shown by __________.

3. True or False

1. Pure substances have a fixed composition.
2. Mixtures can be separated by physical methods.
3. Air is a heterogeneous mixture.
4. A saturated solution can dissolve more solute at the same temperature.
5. Filtration can separate dissolved salt from water.
6. Crystallisation produces pure crystals.
7. Oil and water can be separated using a separating funnel.
8. Colloidal particles settle on standing.
9. Suspensions can be separated by filtration.
10. Distillation works on the difference in boiling points.

4. Match the Following

5. Very Short Answer Questions

1. Define a pure substance.
2. What is a mixture?
3. Differentiate between a solute and a solvent.
4. Define concentration of a solution.
5. What is solubility?
6. What is a saturated solution?
7. State one use of filtration.
8. Why is crystallisation preferred over evaporation?
9. What is paper chromatography?
10. What is the Tyndall effect?

6. Short Answer Questions

1. Differentiate between pure substances and mixtures.
2. Differentiate between homogeneous and heterogeneous mixtures.
3. Explain the formation of a solution with suitable examples.
4. Describe the factors affecting solubility.
5. Differentiate between saturated and unsaturated solutions.
6. Explain the process of filtration with a labelled diagram.
7. Differentiate between evaporation and crystallisation.
8. Describe the principle of distillation.
9. Explain the working of a separating funnel.
10. Differentiate between solution, colloid and suspension.

7. Long Answer Questions

1. Explain the classification of mixtures with suitable examples.
2. Describe the concepts of solution, solute, solvent and concentration.
3. Explain the different methods used for separating mixtures.
4. Describe distillation and fractional distillation with suitable applications.
5. Explain paper chromatography and its uses.
6. Describe the preparation of pure crystals by crystallisation.
7. Differentiate between solution, colloid and suspension using a comparison table.
8. Explain the importance of separation techniques in daily life and industries.
9. How do physical properties help in selecting a suitable separation technique?
10. Discuss the practical applications of different separation methods.

8. Case Study Questions

Case Study – 1

A student mixes sand and water in a beaker. After leaving the mixture undisturbed for some time, the sand settles at the bottom.

1. Name the process responsible for the settling of sand.
2. What is the process of pouring the clear water into another container called?
3. Which method can completely separate the sand from water?
4. Why is this method suitable?

Case Study – 2

A chemist prepares a saturated solution of copper sulphate and allows it to cool slowly. After some time, beautiful blue crystals are formed.

1. Name the process shown above.
2. Why are crystals formed?
3. State one advantage of this method over evaporation.
4. Name one practical application of crystallisation.

Case Study – 3

A refinery separates crude oil into petrol, diesel, kerosene and other useful products.

1. Which separation method is used?
2. On which physical property does this method depend?
3. Why is ordinary distillation not suitable?
4. Name one other industrial application of this method.

Case Study – 4

A student puts a drop of black ink on chromatography paper and dips it in a suitable solvent. After some time, different coloured spots appear.

1. Name the technique used.
2. Why do different colours separate?
3. Name one field where this technique is used.
4. What property of substances helps in this separation?

Case Study – 5

Milk appears uniform to the naked eye but scatters a beam of light passing through it.

1. What type of mixture is milk?
2. Name the phenomenon responsible for scattering of light.
3. Do the particles settle on standing?
4. Can milk be separated by ordinary filtration?

9. Competency-Based Questions

1. Why are mixtures separated before using them in daily life?
2. How does the nature of a mixture determine the separation method?
3. Why is filtration not suitable for separating salt from salt solution?
4. How does boiling point help in distillation?
5. Why is crystallisation preferred for obtaining pure solids?
6. How does chromatography help forensic scientists?
7. Why is milk classified as a colloid and not as a true solution?
8. How does centrifugation help in the dairy industry?
9. How are separation techniques useful in environmental protection?
10. How do physical properties make separation of mixtures possible?

10. HOTS Questions

1. Why is it impossible to separate the components of a pure substance by physical methods?
2. A student tries to separate sugar from sugar solution using filtration. Explain why the attempt fails.
3. Why is fractional distillation preferred for separating petrol from crude oil instead of simple distillation?
4. Can a homogeneous mixture ever be considered a pure substance? Give reasons.
5. How would you separate a mixture containing iron filings, sand and common salt? Explain the complete sequence.
6. Why do colloids scatter light while true solutions do not?
7. How would you decide the best separation method for an unknown mixture?
8. Why are separation techniques considered essential for modern industries?
9. Explain why understanding the physical properties of substances is important before selecting a separation technique.
10. How do different separation methods contribute to sustainable use of natural resources?