NCERT Solutions Class 9 Science Chapter 2 Is Matter Around Us

NCERT Solutions Class 9 Science Chapter 2 Is Matter Around Us Pure helps students clearly understand the basic concepts of chemistry, including pure substances, mixtures, solutions, and methods of separation. 

The NCERT Science Class 9 Chapter 2 Question Answer section is prepared strictly according to the CBSE Class 9 Science Syllabus and explains each question in simple language. 

NCERT Solutions for Class 9 Science Chapter 2 Question Answer 

NCERT Science Class 9 Chapter 2 Question Answer provides detailed and accurate answers to all the questions in Chapter 2, “Is Matter Around Us Pure?”. The solutions explain different types of mixtures such as solutions, colloids, and suspensions. Is Matter Around Us Pure Question Answers help students prepare effectively for exams with step-by-step explanations.

Question 1. What is meant by a substance?

Solution : Substance can be defined as that kind of matter where constituent particles cannot be separated from each other by any physical process since they are all similar in chemical properties.

Question 2. List the points of

between homogeneous and heterogeneous mixtures.

Solution :

CBSE Class 9 Science Exercise-2.2 Page: 18

Question 1. Differentiate between homogeneous and heterogeneous mixtures with examples.

Solution :

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

Solution :

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

Solution :

Mass of sodium chloride (solute) = 36 g Mass of water (solvent) = 100 g Mass of solution = 36 + 100 = 136 g Therefore, concentration percentage = mass of solute/mass of solution = 26.47 %

CBSE Class 9 Chemistry Notes

Exercise-2.3 Page: 19

Question 1. Classify the following as chemical or physical 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 the water breaking down into hydrogen and oxygen gases,
• dissolving common salt in water,
• making a fruit salad with raw fruits, and
• burning of paper and wood.

Solution :

cutting of trees = chemical change
melting of butter in a pan = physical change
rusting of almirah = chemical change boiling of water to form steam = physical change
passing of electric current, through water and the water breaking down into hydrogen and oxygen gases = chemical change
dissolving common salt in water = physical change
making a fruit salad with raw fruits = physical change
burning of paper and wood = chemical change

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

Solution :

Pure substance: Water, salt, sugar Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food

Exercise Questions Page: 22

Question 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) Evaporation (b) Sublimation (c) Filtration (d) Chromatography (e) Centrifugation (f) Separating funnel (g) Filtration (h) Magnetic separation (i) Winnowing/ sedimentation (j) Decantation and filtration 

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

Solution : Take more amount of solvent (water) in a pan and after heating it add little amount of solute (sugar) to the solvent. Solute will dissolve completely in the solvent forming true solution, then add tea leaves that are insoluble along with another soluble liquid milk. After boiling allow filtration with a sieve so the filtrate you obtain is tea while the residue has tea leaves that are thrown away.

Question 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 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 313 K? (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. What 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) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need 62 x 50 = 31 grams of potassium nitrate 100 (b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with decrease in temperature. (c) (i)   Solubility of Potassium nitrate at 293 K is 32 grams. (ii)  Solubility of Sodium chloride at 293 K is 36 grams. (iii) Solubility of Potassium chloride at 293 K is 35 grams. (iv) Solubility of Ammonium chloride at 293 K is 37 grams. The solubility of Ammonium chloride is highest at this temperature. (d) The solubility of salt increases with increase in temperature. 

Question 4. Explain the following giving examples. (a) saturated solution (b) pure substance (c) colloid (d) suspension

Solution :

(a) saturated Solution :- It is a solution in which no more solute particles can be dissolved at a particular temperature.

(b) pure substance :- Such substance that has a uniform composition i.e. has particles with identical properties is called pure substance eg sugar, salt, water, nitrogen etc.

(c) Colloid :- A colloid is a heterogeneous mixture. The size of the solutes in this mixture is so small that they cannot be seen individually with naked eyes, and seems to be distributed uniformly throughout the mixture. The solute particles do not settle down when the mixture is left undisturbed. This means that colloids are quite stable. Colloids cannot be separated by the process of filtration. They can be separated by centrifugation. Colloids show the Tyndall effect. For example, milk, butter, foam, fog, smoke, clouds.

(d) Suspension :- Suspensions are heterogeneous mixtures. The solute particles in this mixture remain suspended throughout the bulk of the medium. The particles can be seen with naked eyes. Suspension shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. This means that suspensions are unstable. Suspensions can be separated by the method of filtration. For example, mixtures of chalk powder and water, wheat flour and water.

Question 5. Classify each of the following as a homogeneous or heterogeneous mixture. soda water, wood, air, soil, vinegar, filtered tea.

Solution :

Homogeneous mixtures: Soda water, air, vinegar Heterogeneous mixtures: Wood, soil, filtered tea 

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

Solution : If we allow the given liquid to evaporate by heating it as in a clean china dish so:

Any residue remaining in the china dish will indicate that water is not pure but contains impurities. O no residue in the china dish will indicate that water is pure.

Question 7. Which of the following materials fall in the category of a “pure substance”? (a) Ice (b) Milk (c)Iron (d)Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Brick (h) Wood (i) Air.

Solution : Pure substances are: ice, iron, hydrochloric acid, calcium oxide, mercury.

Question 8. Identify the solutions among the following mixtures.(a) Soil(b) Sea water(c) Air(d) Coal(e) Soda water.

Solution : Sea water, air and soda water are solutions.

Question 9. Which of the following will show “Tyndall effect”?(a) Salt solution(b)Milk(c) Copper sulphate solution(d) Starch solution.

Solution : Milk and starch solution have larger particles since they are not true solutions so they will show tyndall effect.

Question 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 :

Elements :

Compounds :

Mixtures :

Question 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 a candle.

Solution :

The following changes are chemical changes: (a) Growth of a plant (b) Rusting of iron (d) Cooking of food (e) Digestion of food (g) Burning of candle