A mixture is a combination of two or more substances that are not chemically combined and can be separated by physical methods. Important Questions Class 9 Science Chapter 5 cover Exploring Mixtures and their Separation, including homogeneous mixtures, heterogeneous mixtures, solutions, suspensions, colloids, solubility, separation techniques, and Tyndall effect.
Sugar water looks uniform. Sand and water do not. Milk looks uniform to the eye, but a beam of light can reveal that it behaves differently from saltwater.
Class 9 Science Chapter 5 helps students classify mixtures and choose the correct separation method. The chapter becomes easier when students connect each technique to the property it uses, such as solubility, density, boiling point, sublimation, particle size, or light scattering.
Key Takeaways
| Detail |
Information |
| Chapter |
Class 9 Science Chapter 5 |
| Topic |
Exploring Mixtures and their Separation |
| Syllabus |
CBSE 2026 |
| Question Types |
VSA, Short Answer, Long Answer, Diagram-Based, Assertion-Reason, Case Study |
| Main Concepts |
Mixtures, Solutions, Suspensions, Colloids, Separation Techniques |
| High-Value Topics |
Tyndall Effect, Crystallization, Distillation, Chromatography, Centrifugation |
| Best Revision Method |
Learn mixture type first, then match each technique with the property it uses |
Class 9 Science Chapter List
Class 9 Science Chapter 5 Exploring Mixtures and their Separation: Topics Covered
Class 9 science chapter 5 important questions with answers usually test classification, comparison, separation method selection, and diagram labelling.
Revise these topics before solving the question bank.
- Homogeneous and heterogeneous mixtures
- Solutions, suspensions, and colloids
- Solute, solvent, and solubility
- Saturated and unsaturated solutions
- Concentration of solution
- Solubility curves
- Crystallization and evaporation
- Distillation and fractional distillation
- Paper chromatography
- Separating funnel
- Sublimation and deposition
- Centrifugation
- Coagulation
- Tyndall effect
- Real-life applications of separation techniques
Important Questions Class 9 Science Chapter 5 with Answers
Important Questions Class 9 Science Chapter 5 should be revised in order. Start with mixture definitions, then solution-suspension-colloid comparison, then separation techniques, diagrams, assertion-reason, and case studies.
These class 9 science chapter 5 question answer sets cover both direct recall and application-based questions.
Very Short Answer Important Questions Class 9 Science Chapter 5
Very short answer questions test definitions, examples, and key terms.
Keep answers short, but include the exact scientific term.
Class 9 Science Chapter 5 Important Questions with Answers
Q1. What is a mixture?
Ans. A mixture is a combination of two or more substances that are not chemically combined.
The components retain their individual properties and can be separated by physical methods.
Q2. Give one example each of a homogeneous and heterogeneous mixture.
Ans. Homogeneous mixture: saltwater.
Heterogeneous mixture: sand and water.
Q3. What is a solution?
Ans. A solution is a homogeneous mixture of two or more substances.
The solute dissolves completely in the solvent and forms a uniform mixture.
Q4. What is the Tyndall effect?
Ans. The Tyndall effect is the scattering of light by colloidal particles.
It makes the path of light visible in a colloid.
Q5. Name the separation technique used to separate cream from milk.
Ans. Centrifugation is used to separate cream from milk.
The denser component moves outward, while the lighter cream collects separately.
Q6. What is sublimation?
Ans. Sublimation is the direct conversion of a solid into vapour without changing into liquid.
It is used to separate a sublimable solid from a non-sublimable solid.
Q7. Define solubility.
Ans. Solubility is the maximum amount of solute that dissolves in 100 g of solvent at a particular temperature.
Q8. What is a saturated solution?
Ans. A saturated solution contains the maximum amount of dissolved solute at a given temperature.
No more solute can dissolve in it at that temperature.
Short Answer Questions Class 9 Science Chapter 5
Short answer questions test comparisons and reasons.
Use examples like saltwater, muddy water, milk, fog, ink, oil-water, and seawater.
Solution Suspension Colloid Questions Class 9
Q1. Compare solution, suspension, and colloid.
Ans.
| Feature |
Solution |
Suspension |
Colloid |
| Particle size |
Less than 1 nm |
More than 100 nm |
1 to 100 nm |
| Appearance |
Clear and transparent |
Cloudy or opaque |
Clear or cloudy |
| Settling |
Does not settle |
Settles on standing |
Does not settle |
| Tyndall effect |
Absent |
Usually visible but particles settle |
Present |
| Filtration |
Cannot be filtered |
Can be filtered |
Cannot be filtered by ordinary filter paper |
| Example |
Saltwater |
Chalk in water |
Milk, fog, blood |
Q2. Why is crystallization preferred over simple evaporation to obtain pure salt?
Ans. Simple evaporation removes solvent but leaves impurities with the solid.
Crystallization allows pure crystals to form slowly from a saturated solution. Impurities remain in the mother liquor.
So, crystallization gives a purer product.
Q3. How does paper chromatography separate components of a mixture?
Ans. Paper chromatography separates components based on their different solubilities in a solvent.
The solvent rises through the paper by capillary action. More soluble components travel farther, while less soluble components stay near the baseline.
This forms separate bands.
Q4. What property does a separating funnel use?
Ans. A separating funnel uses immiscibility and density difference.
The denser liquid forms the lower layer. The lighter liquid forms the upper layer.
The lower layer is released first through the tap.
Q5. Why does milk show the Tyndall effect but saltwater does not?
Ans. Milk is a colloid, so its particles are large enough to scatter light.
Saltwater is a true solution. Its particles are too small to scatter light.
Therefore, milk shows the Tyndall effect, but saltwater does not.
Q6. What is coagulation? Give one example.
Ans. Coagulation is the clumping of colloidal particles after adding an electrolyte.
Example: Alum is added to muddy water. Clay particles clump together, become heavy, and settle down.
Long Answer Important Questions Class 9 Science Chapter 5
Long answers should explain the principle, process, and use of the separation method.
Add labelled diagram points wherever the question asks for a setup.
Distillation Chromatography Questions Class 9
Q1. Describe the process of distillation with a labelled diagram description. When is it used?
Ans. Distillation separates two miscible liquids with different boiling points.
Setup:
- A round-bottom flask contains the mixture.
- A thermometer measures vapour temperature.
- A condenser cools the vapour.
- A receiver collects the distillate.
Process:
The mixture is heated. The liquid with the lower boiling point vaporises first. The vapour enters the condenser and cools into liquid.
This liquid is collected in the receiver as distillate. The higher boiling point liquid remains in the flask.
Distillation is used to separate alcohol and water, acetone and water, and pure water from saltwater.
Labels to include: round-bottom flask, thermometer, condenser, water inlet, water outlet, receiver, heating source.
Q2. Explain paper chromatography with a diagram description.
Ans. Paper chromatography separates components of a mixture based on their different movement through paper using a solvent.
Setup:
A pencil baseline is drawn near the bottom of chromatography paper. A spot of mixture is placed on the baseline. The paper is dipped in solvent, but the spot should remain above the solvent level.
Process:
The solvent rises through the paper by capillary action. It carries mixture components upward.
More soluble components move farther. Less soluble components remain closer to the baseline.
After drying, separate coloured bands appear.
Uses:
- Separating pigments in ink
- Separating leaf pigments
- Testing food colours
- Forensic analysis
Labels to include: chromatography paper, pencil baseline, sample spot, solvent, solvent front, separated bands.
Diagram-Based Questions Class 9 Science Chapter 5
Diagram questions are scoring when labels are correct.
Practise separating funnel, distillation setup, paper chromatography, and sublimation setup.
Separating Funnel Diagram Questions Class 9
A separating funnel separates immiscible liquids.
It works only when liquids form separate layers.
Q1. Draw and label a separating funnel. State the principle it uses.
Ans. Labels to include: separating funnel, stopper, tap, stand, beaker, upper liquid layer, lower liquid layer.
Principle:
A separating funnel uses immiscibility and density difference.
The denser liquid settles below. The lighter liquid floats above.
Opening the tap releases the lower layer first.
Q2. Give two mixtures that can be separated by a separating funnel.
Ans.
- Oil and water
- Kerosene and water
In both mixtures, the liquids are immiscible and form separate layers.
Distillation Diagram Questions Class 9
A distillation setup separates a liquid from a mixture by boiling point difference.
The vapour condenses and collects as distillate.
Q1. Draw and label a distillation setup. Name the component collected in the receiver.
Ans. Labels to include: round-bottom flask, thermometer, condenser, water inlet, water outlet, receiver, heating source.
The component with the lower boiling point vaporises first.
It condenses in the condenser and collects in the receiver as distillate.
Paper Chromatography Diagram Questions Class 9
Paper chromatography separates coloured components of a mixture.
It is often asked with ink or plant pigments.
Q1. Draw a paper chromatography setup. What does the position of each band indicate?
Ans. Labels to include: chromatography paper, pencil baseline, sample spot, solvent, solvent front, coloured bands.
Each band represents a different component.
A band higher up has greater solubility in the solvent. A band near the baseline has lower solubility.
The number of bands shows the number of separated components.
Sublimation Diagram Questions Class 9
Sublimation separates a sublimable solid from a non-sublimable solid.
Common examples include ammonium chloride with salt and naphthalene with sand.
Q1. Draw a sublimation setup and explain how it works.
Ans. Labels to include: china dish, mixture, inverted funnel, cotton plug, heating source, deposited solid.
The mixture is heated gently.
The sublimable solid changes directly into vapour. The vapour rises and deposits as solid on the cooler inner surface of the funnel.
The non-sublimable solid remains in the china dish.
Important Questions on Mixtures Class 9 Science
Mixture questions test whether students can classify substances correctly.
Always explain whether the composition is uniform or non-uniform.
Homogeneous Mixture Questions Class 9 Science
A homogeneous mixture has the same composition throughout.
No separate components are visible.
Q1. What is a homogeneous mixture? Give three examples.
Ans. A homogeneous mixture has uniform composition throughout.
All parts look and behave the same.
Examples: saltwater, sugar solution, and air.
Q2. Why is air a homogeneous mixture even though it contains many gases?
Ans. Air contains gases such as nitrogen, oxygen, carbon dioxide, and water vapour.
These gases are evenly distributed in normal conditions.
So, air has uniform composition and is a homogeneous mixture.
Heterogeneous Mixture Questions Class 9 Science
A heterogeneous mixture has non-uniform composition.
Its components may be visible or may settle on standing.
Q1. What is a heterogeneous mixture? Give three examples.
Ans. A heterogeneous mixture has non-uniform composition.
Different parts may look or behave differently.
Examples: sand and water, oil and water, and soil.
Q2. Why is sand and water heterogeneous but saltwater is not?
Ans. Sand does not dissolve in water.
Its particles remain visible and settle on standing.
Salt dissolves completely in water and spreads uniformly. So, saltwater is homogeneous.
Solution, Suspension and Colloid Questions Class 9
Solutions, suspensions, and colloids are often compared in exams.
The key differences are particle size, settling, filtration, and Tyndall effect.
Solution Suspension Colloid Questions Class 9
Q1. A student shines a torch through saltwater, muddy water, and milk. Which shows the Tyndall effect?
Ans. Milk shows the Tyndall effect because it is a colloid.
Its particles scatter light and make the beam visible.
Saltwater is a true solution, so it does not show the Tyndall effect.
Muddy water is a suspension. It may scatter light, but particles settle on standing.
Solubility and Concentration Questions Class 9 Science
Solubility questions test temperature, saturation, and solution concentration.
Read whether the question asks for solubility or concentration.
Solubility Curve Questions Class 9 Science
A solubility curve shows how solubility changes with temperature.
It helps identify saturated, unsaturated, and supersaturated solutions.
Q1. What information does a solubility curve provide?
Ans. A solubility curve shows how much solute dissolves in 100 g of solvent at different temperatures.
Points on the curve represent saturated solutions.
Points below the curve represent unsaturated solutions.
Points above the curve represent supersaturated solutions.
Q2. The solubility of potassium nitrate at 30°C is 45 g per 100 g of water. What does this mean?
Ans. It means that at 30°C, a maximum of 45 g of potassium nitrate dissolves in 100 g of water.
If more than 45 g is added, the extra solid remains undissolved.
Saturated Solution Questions Class 9 Science
A saturated solution contains the maximum amount of solute at a given temperature.
Changing temperature can change its solubility.
Saturated and Unsaturated Solution Questions
Q1. How can you convert a saturated solution into an unsaturated solution?
Ans. Heat the saturated solution.
For most solids, solubility increases with temperature.
So, more solute can dissolve, and the solution becomes unsaturated.
Q2. How are crystals obtained from a saturated solution?
Ans. Cool the saturated solution slowly.
As temperature decreases, solubility decreases.
The extra solute separates out as pure crystals.
Concentration of Solution Questions Class 9 Science
Concentration tells how much solute is present in a solution.
It can be expressed as mass percentage.
Concentration Questions Class 9
Q1. Calculate the concentration of a solution with 10 g of NaCl in 90 g of water.
Ans.
Mass of solute = 10 g
Mass of solvent = 90 g
Mass of solution = 10 + 90 = 100 g
Concentration = Mass of solute / Mass of solution × 100
= 10 / 100 × 100
= 10%
Q2. What happens to concentration when more solvent is added?
Ans. The amount of solute remains the same.
The total mass of solution increases.
So, concentration decreases and the solution becomes more dilute.
Separation Techniques Important Questions Class 9
Separation techniques questions class 9 always connect a method to a physical property.
Use boiling point for distillation, density for separating funnel, solubility for chromatography, and sublimability for sublimation.
Crystallization Questions Class 9 Science
Crystallization is used to obtain pure crystals from an impure sample.
It is better than evaporation when purity matters.
Q1. Describe the steps of crystallization with an example.
Ans.
- Dissolve the impure solid in minimum hot solvent.
- Make a saturated solution.
- Filter the hot solution to remove insoluble impurities.
- Cool the filtered solution slowly.
- Pure crystals form as solubility decreases.
- Filter and dry the crystals.
Example: Obtaining pure copper sulphate crystals from an impure sample.
Q2. Why is crystallization used instead of evaporation to purify sugar?
Ans. Evaporation removes the solvent and leaves both sugar and impurities behind.
Crystallization allows pure sugar crystals to form slowly.
Impurities remain dissolved in the mother liquor.
Evaporation Questions Class 9 Science
Evaporation separates a non-volatile solute from a volatile solvent.
It is useful when a very pure product is not required.
Q1. When is evaporation used as a separation method?
Ans. Evaporation is used when the solvent is volatile and the solute is non-volatile.
Example: Common salt is obtained from seawater by evaporation.
The water evaporates, and salt remains behind.
Distillation Questions Class 9 Science
Distillation separates miscible liquids with different boiling points.
It can also separate a liquid from a dissolved solid.
Q1. Name two mixtures that distillation can separate. State the property it uses.
Ans. Distillation can separate alcohol and water, and acetone and water.
It uses difference in boiling points.
The liquid with the lower boiling point vaporises first and is collected as distillate.
Q2. What is fractional distillation? When is it needed?
Ans. Fractional distillation separates miscible liquids with close boiling points.
It uses a fractionating column where repeated vaporisation and condensation occur.
It is used to separate crude oil fractions and components of liquid air.
Paper Chromatography Questions Class 9 Science
Chromatography is useful for separating small amounts of coloured substances.
It works even when components are present in tiny quantities.
Q1. A student runs chromatography on black ink and sees three bands: blue at the top, red in the middle, and yellow near the baseline. What does this show?
Ans. Black ink contains three pigments: blue, red, and yellow.
Blue travelled farthest, so it is most soluble in the solvent.
Yellow stayed near the baseline, so it is least soluble.
Paper chromatography separated the pigments into distinct bands.
Heterogeneous Mixture Separation Questions Class 9
Different heterogeneous mixtures need different methods.
Identify whether the components differ in size, density, magnetism, solubility, or sublimability.
Separating Funnel Questions Class 9 Science
A separating funnel works only for immiscible liquids.
It cannot separate liquids that mix completely.
Q1. Why can a separating funnel not separate ethanol and water?
Ans. Ethanol and water are miscible liquids.
They mix completely and form a homogeneous mixture.
A separating funnel works only for immiscible liquids that form separate layers.
Ethanol and water should be separated by distillation.
Sublimation Questions Class 9 Science
Sublimation separates substances that directly change from solid to vapour.
The other component should not sublime.
Q1. Name two substances separable by sublimation and explain why.
Ans.
- Ammonium chloride from salt: Ammonium chloride sublimes, but salt does not.
- Naphthalene from sand: Naphthalene sublimes, but sand does not.
On heating, the sublimable solid changes into vapour and deposits separately on cooling.
Centrifugation Questions Class 9 Science
Centrifugation separates components by density using high-speed spinning.
It is faster than natural settling.
Q1. Explain the principle and uses of centrifugation.
Ans. Centrifugation spins a mixture at high speed.
The denser particles move outward and settle. The lighter component remains near the top or centre.
Uses:
- Separating cream from milk
- Separating blood cells from plasma
- Separating fine clay particles from water
Coagulation Questions Class 9 Science
Coagulation helps settle colloidal particles.
It is commonly used in water purification.
Q1. What is coagulation? How does alum purify muddy water?
Ans. Coagulation is the clumping of colloidal particles after adding an electrolyte.
Alum neutralises the charge on clay particles in muddy water.
The particles clump together, become heavy, and settle down.
This makes the water clearer.
Tyndall Effect Important Questions Class 9 Science
Tyndall effect questions class 9 are important for identifying colloids.
The effect depends on particle size and light scattering.
Tyndall Effect in Colloids Questions Class 9
A colloid shows the Tyndall effect because its particles are large enough to scatter light.
True solutions do not show it.
Q1. What causes the Tyndall effect? Why does it not occur in a true solution?
Ans. The Tyndall effect is caused by scattering of light by colloidal particles.
Colloidal particles are large enough to scatter light.
Particles in a true solution are too small to scatter light. So, true solutions do not show the Tyndall effect.
Q2. Give three real-life examples of the Tyndall effect.
Ans.
- Sunlight passing through a dusty room
- Car headlights in fog
- Projector beam visible in a cinema hall
In each case, tiny particles scatter light and make the beam visible.
Solution Suspension Colloid Difference Questions Class 9
The Tyndall effect is a simple test to identify colloids.
It helps distinguish a colloid from a true solution.
Q1. How can you distinguish a solution from a colloid using a simple test?
Ans. Shine a torch beam through both mixtures.
In a true solution, the beam is not visible.
In a colloid, the beam becomes visible due to scattering of light.
This visible beam confirms the Tyndall effect.
Class 9 Science Chapter 5 Assertion Reason Questions
Assertion-reason questions test whether the reason explains the assertion.
Read both statements separately before choosing the answer.
Directions:
(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.
Class 9 Science Chapter 5 Assertion Reason Questions
Q1. Assertion (A): Milk shows the Tyndall effect but saltwater does not. Reason (R): Milk is a colloid with particles large enough to scatter light. Saltwater is a solution with particles too small to scatter light.
Ans. (a)
Both A and R are true, and R correctly explains A.
Q2. Assertion (A): Crystallization gives a purer product than evaporation. Reason (R): In crystallization, only the pure substance forms crystals while impurities remain dissolved in the mother liquor.
Ans. (a)
Both A and R are true, and R correctly explains A.
Q3. Assertion (A): A separating funnel cannot separate ethanol from water. Reason (R): Ethanol and water are miscible liquids and do not form separate layers.
Ans. (a)
Both A and R are true, and R correctly explains A.
Q4. Assertion (A): Centrifugation separates cream from milk faster than natural settling. Reason (R): Centrifugal force separates components faster than gravity alone.
Ans. (a)
Both A and R are true, and R correctly explains A.
Q5. Assertion (A): Sublimation can separate iodine from sand. Reason (R): Iodine sublimes directly from solid to vapour on heating, but sand does not.
Ans. (a)
Both A and R are true, and R correctly explains A.
Case Study Questions Class 9 Science Chapter 5
Case study questions connect mixture properties with real-life situations.
Read the passage and identify the separation principle before answering.
Case Study 1: Blood Sample Processing in Hospitals
When a patient gives a blood sample, the laboratory technician places it in a centrifuge tube. The machine spins the sample at high speed. Heavier blood cells settle at the bottom, while lighter plasma collects at the top.
Q1. Which separation technique is used here?
Ans. Centrifugation is used.
It separates blood cells from plasma using density difference and high-speed spinning.
Q2. Why is gravity not sufficient to separate plasma from blood cells quickly?
Ans. Blood cells are very small.
Their density difference from plasma is not enough for quick separation by gravity.
Centrifugation creates a stronger separating force, so the process becomes faster.
Q3. What type of mixture is blood?
Ans. Blood is a colloidal mixture.
It contains cells and other particles dispersed in plasma.
Case Study 2: Salt Extraction from Seawater
A salt factory pumps seawater into large shallow ponds. Sunlight evaporates water slowly over several days. Salt deposits as the solution becomes saturated. The crude salt is then purified by crystallization.
Q1. Why does salt deposit when water evaporates?
Ans. Evaporation removes water from seawater.
As water decreases, the solution becomes saturated.
Further evaporation causes dissolved salt to deposit as solid.
Q2. Why does the factory use crystallization after evaporation?
Ans. Crude salt contains impurities.
Crystallization helps obtain purer salt crystals.
The impurities remain dissolved in the mother liquor or are removed by filtration.
Q3. Which property of seawater makes evaporation useful for salt extraction?
Ans. Water is volatile and evaporates.
Salt is non-volatile and remains behind.
This difference allows salt to be separated from seawater.
Important Definitions Class 9 Science Chapter 5
| Term |
Definition |
| Mixture |
Combination of two or more substances not chemically combined |
| Homogeneous mixture |
Mixture with uniform composition throughout |
| Heterogeneous mixture |
Mixture with non-uniform composition |
| Solution |
Homogeneous mixture where solute dissolves completely in solvent |
| Suspension |
Heterogeneous mixture whose particles settle on standing |
| Colloid |
Mixture with particle size between solution and suspension |
| Solubility |
Maximum solute that dissolves in 100 g solvent at a given temperature |
| Saturated solution |
Solution containing maximum dissolved solute at a given temperature |
| Crystallization |
Formation of pure crystals from a saturated solution |
| Tyndall effect |
Scattering of light by colloidal particles |
| Centrifugation |
Separation by high-speed spinning based on density |
| Coagulation |
Clumping of colloidal particles after adding an electrolyte |
| Chromatography |
Separation based on different movement rates through a stationary phase |
| Sublimation |
Direct conversion of solid to vapour without liquid state |
| Distillation |
Separation based on difference in boiling points |