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We are providing NCERT Solutions Class 9 Science Chapter 2 ‘Is Matter Around Us Pure?’ to help you navigate through your school exams. You can also download a PDF for important questions and answers for quick revision. Let us get started!
Download the NCERT Solutions of Class 9 Science Chapter 2 PDF Here!
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| Chapter 1 | Chapter 2 | Chapter 3 | Chapter 4 | Chapter 5 | Chapter 6 |
| Chapter 7 | Chapter 8 | Chapter 9 | Chapter 10 | Chapter 11 | Chapter 12 |
NCERT Solutions Class 9 Science Chapter 2 Is Matter Around Us Pure?
Here are NCERT Solutions of Class 9 Science Chapter 2 ‘Is Matter Around Us Pure?’ to the questions in the exercise section of the lesson.
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 can be separated from its solution in water through the process of evaporation.
(b) The sublimation technique can be used as Ammonium chloride supports Sublimation.
(c) Small pieces of metal in the engine oil of a car can be filtered manually.
(d) Chromatography can be used to extract different pigments from flower petals.
(e) The technique of centrifugation can be used to separate butter from curd.
(f) Oil and water do not mix, hence funnel can be used to separate them.
(g) Tea leaves can be manually separated from tea using simple filtration methods.
(h) Iron pins can be separated from sand using a magnet or manually.
(i) They can separated by using the method of winnowing.
(j) By using sedimentation or decantation, fine mud particles suspended in water can be separated.
2. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue.
Solution:
(a) Add a cup of milk to a vessel, which is the solvent, and heat it.
(b) Tea leaves to be added next, they will act as the solute.
(c) The solute, i.e., the tea powder, remains insoluble in the milk, which can be observed while it is still boiling.
(d) Now, sugar will be added and some stirring is done.
(e) Sugar is soluble in the solvent i.e. milk.
(f) Continuous stirring causes the sugar to dissolve completely in the tea solution, reaching saturation.
(g) After the boiling of tea, all the contents are filtered through a strainer to get the tea solution. Tea leaves will remain as residue and are collected in the filtrate.
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).
| Substance dissolved | Temperature in K | ||||
| 283 | 293 | 313 | 333 | 353 | |
| Solubility | |||||
| Potassium nitrate | 21 | 32 | 62 | 106 | 167 |
| Sodium chloride | 36 | 36 | 36 | 37 | 37 |
| Potassium chloride | 35 | 35 | 40 | 46 | 54 |
| Ammonium chloride | 24 | 37 | 41 | 55 | 66 |
(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 required to produce a saturated solution in 100 g of water at 313 K = 62g
To find:
Mass of potassium nitrate required to produce a saturated solution in 50 g of water =?
Required amount = 62 x 50/100 = 31
Hence, 31 g of potassium nitrate is required.
(b) As the saturated solution of potassium chloride cools, Pragya would observe crystals of potassium chloride. This is because, with decreased temperature, the solubility of potassium chloride decreases in the saturated solution.
(c) According to the given data,
Solubility of potassium nitrate at 293K = 32 g
Solubility of sodium chloride at 293K = 36 g
Solubility of potassium chloride at 293K = 35 g
Solubility of ammonium chloride at 293K = 37g
It is easily observable from this data that ammonium chloride has the highest solubility at 293K.
(d) From the table, we can observe that the solubility of salts increases with the increase in temperature. At a particular temperature, when a salt reaches its saturation point, we can increase its solubility by increasing temperature.
4. Explain the following, giving examples.
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) suspension
Solution:
(a) Saturated solution: The state of a solution at a particular temperature when no more solute is soluble in the solvent is known as saturated solution. Example: After a particular amount, no more salt is soluble in a specific volume of water at a fixed temperature.
(b) Pure substance: A substance can be considered pure when it is formed of only one kind of molecule, atom or compound without any mixture with any other substance or any divergence in the structural arrangement. Examples: Sulphur, potassium etc.
(c) Colloid: A colloid comes in the range of solution and a suspension containing particles ranging from 2 to 1000 nm. These can be differentiated from solutions using the Tyndall effect. Examples: Milk and gelatin.
(d) Suspension: It is a heterogeneous mixture that contains solute particles that are insoluble but are suspended in the medium. The suspended particles are not microscopic but visible to bare eyes and are large enough to undergo sedimentation.
5. Classify each of the following as a homogeneous or heterogeneous mixture.
soda water, wood, air, soil, vinegar, filtered tea.
Solution:
| Homogenous mixture | Heterogeneous mixture |
| Soda water | Wood |
| Vinegar | Soil |
| Filtered tea | |
| Air |
6. How would you confirm that a colourless liquid given to you is pure water?
Solution: We can confirm that a given colourless liquid is pure water by boiling it. If it boils at 100 degrees Celcius, then it can be said to be pure water. If the boiling point deviates from 100 degrees Celcius, then the water is not pure and contains impurities.
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
8. Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water
Solution:
Solutions from the above-mentioned list are:
- 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: Milk and Starch Solution
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 | Mixture |
| Sodium | Calcium carbonate | Soil |
| Silver | Carbon dioxide | Sugar solution |
| Tin | Methane | Coal |
| Silicon | Air | |
| Blood | ||
| Soap |
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: The following are chemical changes:
Growth of a plant, rusting of iron, cooking of food, digestion of food and burning of candles.
Download the NCERT Solutions of Class 9 Science Chapter 2 PDF Here!
Download Solutions of all the Chapters of Class 9 Science:
| Chapter 1 | Chapter 2 | Chapter 3 | Chapter 4 | Chapter 5 | Chapter 6 |
| Chapter 7 | Chapter 8 | Chapter 9 | Chapter 10 | Chapter 11 | Chapter 12 |
Related Reads:
Explore Notes of All subjects of CBSE Class 9:
| CBSE Notes Class 9 English | CBSE Notes Class 9 History | CBSE Notes Class 9 Geography |
| CBSE Notes Class 9 Civics | CBSE Notes Class 9 Mathematics | CBSE Notes Class 9 Science |
FAQs
Ans: No, all the matter around us is not pure. Some of it like elements, etc may be pure but majority of matter is a mixture of substances.
Ans: Elements like Sulphur, Potassium, etc can be considered the purest matter because even by chemicals, they cannot be separated into different substances.
Ans: No, milk is not a pure substance. It can be separated into its constituents such as protein, fat, etc.
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