NCERT solutions for Science [English] Class 9 chapter 2 - Is Matter around us Pure [Latest edition]

What is meant by a substance?

List the points of differences between homogeneous and heterogeneous mixtures with examples.

List the points of differences between homogeneous and heterogeneous mixtures with examples.

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

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.

Classify the following as chemical or physical change: 

Cutting of trees

Classify the following as chemical or physical change: 

Melting of butter in a pan

Classify the following as chemical or physical change: 

Rusting of almirah

Classify the following as chemical or physical change:

Boiling of water to form steam.

Classify the following as chemical or physical change:

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

Classify the following as chemical or physical change: 

Dissolving common salt in water.

Classify the following as chemical or physical change:

Making a fruit salad with raw fruits

Classify the following as chemical or physical change:

Burning of paper and wood

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

Which separation technique will you apply for the separation of the following?

Sodium chloride from its solution in water.

Which separation technique will you apply for the separation of the following?

Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

Which separation technique will you apply for the separation of the following?

Small pieces of metal in the engine oil of a car.

Which separation technique will you apply for the separation of the following?

Different pigments from an extract of flower petals.

Which separation technique will you apply for the separation of the following?

Butter from curd.

Which separation technique will you apply for the separation of the following?

Oil from water.

Which separation technique will you apply for the separation of the following?

Tea leaves from tea.

Which separation technique will you apply for the separation of the following?

Iron pins from sand.

Which separation technique will you apply for the separation of the following?

Wheat grains from husk.

Which separation technique will you apply for the separation of the following?

Fine mud particles suspended in water.

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

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).

1. What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
2. 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.
3. Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
4. What is the effect of change of temperature on the solubility of a salt?

Explain the following giving an example.

Saturated solution

Explain the following giving an example.

Pure substance

Explain the following giving an example.

Colloid

Explain the following giving an example.

Suspension

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

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

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

Which of the following materials fall in the category of a “pure substance”?

1. Ice
2. Milk
3. Iron
4. Hydrochloric Acid
5. Calcium oxide
6. Mercury
7. Brick
8. Wood
9. Air

Identify the solutions among the following mixtures.

1. Soil
2. Sea water
3. Air
4. Coal
5. Soda water

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

1. Salt solution
2. Milk
3. Copper sulphate solution
4. Starch solution

Classify the following into elements, compounds and mixtures:

1. Sodium
2. Soil
3. Sugar solution
4. Silver
5. Calcium carbonate
6. Tin
7. Silicon
8. Coal
9. Air
10. Soap
11. Methane
12. Carbon dioxide
13. Blood

Which of the following are chemical changes?

1. Growth of a plant
2. Rusting of iron
3. Mixing of iron fillings and sand
4. Cooking of food
5. Digestion of food
6. Freezing of water
7. Burning of candle

Take an earthen pot (mutka), some pebbles and sand. Design a small-scale filtration plant that you could use to clean muddy water.