Class 9 Exam  >  Class 9 Notes  >  NCERT Solutions - Matter In Our Surroundings, Science, Class 9

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

 Q1. What is meant by a substance?
Ans.
A pure substance consists of a single type of particles. A substance is a pure single form of matter.

Q2. List the points of differences between homogeneous and heterogeneous mixtures.
Ans.

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

Q3. Differentiate between homogeneous and heterogeneous mixtures with examples.
Ans.

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

Q4. How are sol, solution and suspension different from each other?
Ans.​

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

Q5. To make a saturated solution, 36 g of sodium chloride is dissolved in 100g of water at 293 K. Find its concentration at this temperature.
Ans.
Mass of solute (sodium chloride) = 36 g

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

Q6. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?
Ans.
A mixture of kerosene and petrol which are miscible with each other can be separated by distillation.

Method

  • Take the mixture in a distillation flask.
  • Fit it with a thermometer.
  • Arrange the apparatus as shown in the figure.
  • Heat the mixture slowly.
  • Petrol vaporises first as it has lower boiling point. It condenses in the condenser and is collected from the condenser outlet.
  • Kerosene is left behind in the distillation flask.

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

Q7. Name the technique to separate (i) butter from curd, (5) salt from sea-water, (iii) camphor from salt.
Ans.
(i) Centrifugation, (ii) Evaporation, (iii) Sublimation.

Q8. What type of mixtures are separated by the technique of crystallisation?
Ans.
Crystallisation technique is used to purify solid with some impurities in it. Example: Salt from sea-water

Q9. 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 gas,
  • dissolving common salt in water,
  • making a fruit salad with raw fruits and
  • burning of paper and wood.

Ans.​

Physical Change Chemical Change
  • cutting of trees
  • rusting of almirah
  • melting of butter in a pan
  • passing of electric current through
  • boiling of water to form steam
water and then breaking down
  • dissolving common salt in water
into hydrogen and oxygen gas
  • making a fruit salad with raw fruits
  • burning of paper and wood

 

Q10. Try segregating the things around you as pure substances or mixtures.
Ans.
Pure substances—Water, bread, sugar and gold.
Mixtures—Steel, plastic, paper, talc, milk and air


NCERT Textual Questions Solve

Q1. 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.
Ans.
(a) Evaporation
(b) Sublimation
(c) Filtration
(d) Chromatography
(h) Magnetic separation
(g) Filtration
(e) Centrifugation
(f) Separating funnel
(i) Winnowing/sedimentation
(j) Decantation and filtration.

Q2. Write the steps you would use for making tea. Use the words, solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Ans.
1. Take a cup of water in a container as solvent and heat it.
2. Add sugar in it which is solute. Heat it till all sugar dissolves.
3. You get a solution of water and sugar.
4. Sugar is soluble in water completely.
5. Add half a tea-spoon of tea-leaves, it is insoluble in water.
6. Boil the content, add milk which is also soluble in water, boil again.
7. Filter the tea with the help of strainer, the tea collected in cup is filtrate and the tea leaves collected on the strainer is residue.

Q3. 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).

NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

(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. Which salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt?
Ans
. (a) Mass of KNO3 needed to produce a saturated solution of KNO3 in 100 grams of water at 313 K = 62 g
∴ Mass of KNO3 needed in 50 grams of water at 313 KNCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings
(b) Crystals of potassium chloride will be obtained on cooling the saturated solution.
(c) Solubility of each salt at 293 K is
(i) Potassium nitrate → 32 g
(ii) Sodium chloride → 36 g
(iii) Potassium chloride → 35 g
(iv) Ammonium chloride → 37 g
Ammonium chloride has the highest solubility at this temperature.
(d) On increasing the temperature, solubility of a salt increases.

Q4. Explain the following giving examples: (a) Saturated solution (b) Pure substance (c) Colloid (d) Suspension
Ans.
(a) Saturated solution: In a given solvent when no more solute can dissolve further at a given temperature is called saturated solution.
(b) Pure substance: A pure substance consists of a single type of particles. E.g., gold, silver.
(c) Colloid: A colloid is a solution in which the size of solute particles are bigger than that of true solution. These particles cannot be seen with our naked eyes, they are stable. e.g., ink, blood.
 (d) Suspension: It is a heterogeneous mixture in which the solute particles are big enough to settle down. e.g., chalk-water, paints, etc.

Q5. Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air, soil, vinegar, filtered tea.
Ans.
Homogeneous: Soda water, vinegar, filtered tea, air. Heterogeneous: Wood, soil.

Q6. How would you confirm that a colourless liquid given to you is pure water?
Ans.
By finding the boiling point of a given colourless liquid. If the liquid boils at 100°C at atmospheric pressure, then it is pure water. This is because pure substances have fixed melting and boiling point.

Q7. 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.
Ans.
Pure substances are: Ice, iron, hydrochloric acid, calcium oxide and mercury.

Q8. Identify the solutions among the following mixtures. (a) Soil (b) Sea water (c) Air (d) Coal (e) Soda water.
Ans.
Solutions are: Sea water, soda water and air.

Q9. Which of the following will show “Tyndall effect”? (a) Salt solution (b) Milk (c) Copper sulphate solution (d) Starch solution.
Ans.
Milk and starch solution.

Q10. 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
Ans.​

Elements Compounds Mixtures
Sodium Calcium carbonate Sugar solution
Silver Methane Soil
Tin Carbon dioxide Coal
Silicon Soap Air
    Blood


Q11. 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.
Ans.
Chemical changes are:
(a) Growth of a plant
(b) Rusting of iron
(c) Cooking of food
(d) Digestion of food
(e) Burning of a candle 

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FAQs on NCERT Solutions for Class 9 Science Chapter 1 - Matter In Our Surroundings

1. What is matter and why is it important?
Ans. Matter refers to anything that occupies space and has mass. It can exist in three states - solid, liquid, and gas. Matter is important because everything around us, including ourselves, is made up of matter. Understanding matter helps us comprehend the properties and behaviors of different substances and enables us to study various natural phenomena.
2. What are the characteristics of the three states of matter?
Ans. The three states of matter, namely solid, liquid, and gas, have distinct characteristics. In solids, particles are closely packed together, have a fixed shape and volume, and cannot flow easily. Liquids have particles that are loosely packed, take the shape of their container, have a definite volume, and can flow. Gases have particles that are widely spaced, take the shape and volume of their container, and can flow easily.
3. How does the change of state occur in matter?
Ans. The change of state in matter occurs due to the gain or loss of heat energy. When heat energy is added to a substance, it gains energy and changes its state from solid to liquid (melting) and from liquid to gas (evaporation). On the other hand, when heat energy is removed from a substance, it loses energy and changes its state from gas to liquid (condensation) and from liquid to solid (freezing).
4. What is the difference between evaporation and boiling?
Ans. Evaporation and boiling are both processes of converting a liquid into a gas, but they differ in terms of temperature and occurrence. Evaporation occurs at any temperature below the boiling point of a liquid, where only the surface molecules gain enough energy to escape into the air. On the other hand, boiling occurs at a specific temperature called the boiling point, where the entire liquid rapidly vaporizes, forming bubbles throughout the liquid.
5. How does the process of sublimation occur?
Ans. Sublimation is the process in which a solid directly changes into a gas without first becoming a liquid. It occurs when a solid absorbs heat energy and gains enough energy for its particles to break free from their fixed positions and form a gas. Examples of substances that undergo sublimation include dry ice (solid carbon dioxide) and camphor. Sublimation is an endothermic process, meaning it requires the input of heat energy.
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