NCERT Solutions for Class 9 Science Chapter 2 PDF Download

NCERT Solutions for Class 9 Science Chapter 2:- NCERT Solutions for Class 9 Science Chapter 2 provides straightforward answers and explanations, helping students understand fundamental concepts easily. Covering topics like matter, its properties, and states of matter, these solutions support academic achievement. 

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NCERT Solutions for Class 9 Science Chapter 2

1. What is meant by a substance?

Solution: A substance is a form of matter with a uniform and definite composition. It can be an element or a compound characterised by distinct physical and chemical properties.

2. List the points of difference between homogeneous and heterogeneous mixtures.

Solution:

Exercise-2.2 Page: 18

1. Differentiate between homogenous and heterogeneous mixtures with examples.

Solution: 

2. How are sol, solution and suspension different from each other?

Solution:

3. To make a saturated solution, 36g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

Solution:

• Mass of solute (NaCl) = 36g

• Mass of solvent (H₂O) = 100g

• Mass of solution (NaCl + H₂O) = 136g

Concentration = (Mass of solute / Mass of solution) × 100

Exercise-2.3 Page: 24

1. How will you separate a mixture containing kerosene and petrol (the difference in their boiling points is more than 25°C), which are miscible with each other?

Solution:

Kerosene and petrol, being miscible with a significant difference in boiling points, can be separated using simple distillation. In this process, the mixture is heated in a distillation flask. 

Petrol, with its lower boiling point, evaporates first and is condensed in a condenser. Meanwhile, kerosene, having a higher boiling point, remains in the flask. 

When the boiling points of liquids are closer, fractional distillation is preferred, involving a fractionating column for separation before condensation.

2. Name the techniques used to separate the following:

(a) Butter from curd

(b) Salt from seawater

(c) Camphor from salt

Solution:

a) Centrifugation separates butter from curd based on density differences.

b) Evaporation separates salt from seawater by evaporating the water, leaving solid salt behind.

c) Sublimation separates camphor from salt, as camphor transitions directly from solid to gas without becoming liquid.

3. What types of mixtures are separated by the technique of crystallisation?

Solution: Crystallisation separates solids from a liquid solution, forming highly pure crystals. Unlike precipitation, this technique results in crystal formation, making it ideal for purifying impure substances.

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Exercise-2.4 Page: 24

1. Classify the following as physical or chemical changes:

• Cutting of trees

• Melting of butter in a pan

• Rusting of almirah

• Boiling of water to form steam

• Passing of electric current through water and water breaking into hydrogen and oxygen gases.

• Dissolving common salt in water

• Making a fruit salad with raw fruits, and

• Burning of paper and wood

Solution:

2. Try segregating the things around you as pure substances and mixtures.

Solution: Pure substance: Water, salt, sugar

Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food

Exercise Page: 28

1. Which separation techniques will you apply for the separation of the following?

(a) Sodium chloride from its solution in water.

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

(c) Small pieces of metal in the engine oil of a car.

(d) Different pigments from an extract of flower petals.

(e) Butter from curd.

(f) Oil from water.

(g) Tea leaves from tea.

(h) Iron pins from sand.

(i) Wheat grains from husk.

(j) Fine mud particles suspended in water.

Solution:

(a) Sodium chloride in water can be separated through evaporation.

(b) Sublimation is suitable for separating ammonium chloride.

(c) Metal pieces in engine oil can be manually filtered.

(d) Chromatography can separate various pigments from flower petal extract.

(e) Centrifugation separates butter from curd based on density differences.

(f) A funnel can separate immiscible liquids like oil and water based on density.

(g) Tea leaves can be separated from tea using simple filtration.

(h) Iron pins can be separated from sand using magnets due to their magnetic properties.

(i) Husk and wheat can be separated by winnowing, based on their mass difference.

(j) Sedimentation and decantation can separate water from fine mud particles by allowing the mud to settle and then tilting the clear water out.

2. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue.

Solution:

(a) Heat a cup of milk in a vessel, which acts as the solvent.

(b) Add tea powder or leaves to the boiling milk as the solute and continue heating.

(c) The tea powder remains insoluble in the boiling milk.

(d) Stir in sugar into the boiling solution.

(e) Sugar, a solute, dissolves completely in the solvent.

(f) Continuous stirring saturates the tea solution with dissolved sugar.

(g) Remove the solution from heat, filter to separate tea powder residue from the tea solution containing dissolved sugar in milk.

3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of a substance dissolved in 100 grams of water to form a saturated solution).

(a) What mass of potassium nitrate would be needed to produce a saturated solution of

potassium nitrate in 50 grams of water at 313K?

(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the

solution to cool at room temperature. What would she observe as the solution cools? Explain.

(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this

temperature?

(d) What is the effect of change of temperature on the solubility of a salt?

Solution:

(a) Given:

Mass of potassium nitrate for saturated solution in 100 g water at 313 K = 62 g

To find:

Mass of potassium nitrate for saturated solution in 50 g water = ?

Hence, 31 g of potassium nitrate is required.

(b) Potassium chloride's solubility decreases as its saturated solution cools at 353 K, causing crystals to form due to excess solute.

(c) Solubility data at 293 K:

Potassium nitrate: 32 g

Sodium chloride: 36 g

Potassium chloride: 35 g

Ammonium chloride: 37 g

Ammonium chloride has the highest solubility at 293 K.

(d) Effect of temperature on salt solubility:

Solubility increases with higher temperatures. Raising the temperature allows more salt to dissolve when a solution reaches saturation at a specific temperature.

4. Explain the following, giving examples.

(a) Saturated solution

(b) Pure substance

(c) Colloid

(d) suspension

Solution:  (a) Saturated Solution: No more solvents can dissolve at a given temperature. Example: Carbonated water with carbon dioxide bubbles.

(b) Pure Substance: Composed of identical molecules, atoms, or compounds without impurities. Examples: Sulphur, diamonds.

(c) Colloid: Intermediate between solution and suspension, with particles 2 to 1000 nanometers, showing the Tyndall effect. Examples: Milk, gelatin.

(d) Suspension: Heterogeneous mixture with visible insoluble particles settling over time.

5. Classify each of the following as a homogeneous or heterogeneous mixture.

soda water, wood, air, soil, vinegar, filtered tea.

Solution: Homogeneous Mixture: Soda water, vinegar, filtered tea, air.

Heterogeneous Mixture: Wood, soil.

6. How would you confirm that a colourless liquid given to you is pure water?

Solution: Boiling a colourless liquid at 100°C confirms its purity; any deviation suggests impurities from added water. 

7. Which of the following materials fall into the category of “pure substance”?

(a) Ice

(b) Milk

(c) Iron

(d) Hydrochloric acid

(e) Calcium oxide

(f) Mercury

(g) Brick

(e) Wood

(f) Air.

Solution: The following substances from the above-mentioned list are pure substances:

• Iron

• Ice

• Hydrochloric acid

• Calcium oxide

• Mercury

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8. Identify the solutions among the following mixtures.

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water

Solution: The following are the solutions from the above-mentioned list of mixtures:

• Sea water

• Air

• Soda water

9. Which of the following will show the “Tyndall effect”?

(a) Salt solution

(b) Milk

(c) Copper sulphate solution

(d) Starch solution

Solution: Tyndall effect is exhibited by only milk and starch solution from the above-mentioned list of solutions.

10. Classify the following into elements, compounds and mixtures.

(a) Sodium

(b) Soil

(c) Sugar solution

(d) Silver

(e) Calcium carbonate

(f) Tin

(g) Silicon

(h) Coal

(i)  Air

(j)  Soap

(k) Methane

(l) Carbon dioxide

(m) Blood

Solution:

11. Which of the following are chemical changes?

(a) Growth of a plant 

(b) Rusting of iron

(c) Mixing of iron filings and sand 

(d) Cooking of food

(e) Digestion of food 

(f) Freezing of water

(g) Burning of candle

Solution: Growth of a plant, rusting of iron, cooking of food, digestion of food and burning of candles.

NCERT Solutions for Class 9 Science Chapter 2 FAQs

Q1. What are the main topics covered in NCERT Class 9 Science Chapter 2?

Ans. Chapter 2 covers the basics of matter, its states, properties, and changes.

Q2. Why is understanding matter and its properties important?

Ans. Understanding matter helps explain everyday phenomena and scientific principles.

Q3. How can NCERT Solutions for Class 9 Science Chapter 2 help students?

Ans. These solutions provide step-by-step answers, clarifying concepts and aiding in exam preparation.