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.png "RBSE Class 9 Science Chapter 2 Is Matter around Us Pure Solutions")
These solutions are based on NCERT Class 9 Science book prescribed by Rajasthan Board of Secondary Education. So these RBSE Class 9 Science solutions are very useful for you.
Chapter 2 – Is Matter around Us Pure
Intext Questions
Answer of Questions on Page No. 15
Q.1 What is meant by a substance?
Answer
A pure substance consists of only one type of particles.
Q.2 List the points of differences between homogeneous and heterogeneous mixture.
Answer
Answer of Questions on Page No. 18
Q.1 Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer
Q.2 How are sol, solution and suspension different from each other?
Answer
Q.3 To make a saturated solution, 36g of sodium chloride is dissolved in 100g of water at 293K. Find its concentration at the temperature.
Answer
Given,
Mass of solute (sodium chloride) =36 g
Mass of solvent (water) = 100 g
Mass of solution = Mass of solute + mass of solvent
= 36 g + 100 g
= 136 g
Answer of Questions on Page No. 19
Q.1Classify the following as chemical or physical changes:
1. Cutting of trees.
2. Melting of butter in a pan.
3. Rusting of almirah.
4. Boiling of water to form steam.
5. Passing of electric current, through water and the water breaking down into hydrogen and oxygen gases.
6. Dissolving common salt in water.
7. Making a fruit salad with raw fruits, and
8. Burning of paper and wood.
Answer
Physical change
1. Cutting of trees.
2. Melting of butter in a pan.
3. Boiling of water to form steam.
4. Dissolving common salt in water.
5. Making a fruit salad with raw fruits.
Chemical
change
1. Rusting of almirah.
2. Passing of electric current through water and the water breaking down into hydrogen and oxygen gases
3. Burning of paper and wood.
Q2.Try segregating the things around you as pure substances or mixtures:
Answer
Pure substances:
1. Distilled water
2. Bread
3. Diamond
4. Graphite
5. Sugar
6. Gold
Mixture:
1. Ice-cream
2. Steel
3. Paper
4. Talc
5. Kerosene Oil
6. Solder wire
7. Curd
8. Air
Answer of Questions End Exercises
Q.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 of sodium chloride and ammonium chloride.
(c) Small pieces of metal from in the engine oil of a car.
(d) Different pigment 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.
Answer
(a) Evaporation
(b) Sublimation
(c) Filtration
(d) Chromatography
(e) Centrifugation
(f) Separating funnel
(g) Filtration
(h) Magnetic Separation
(i) Sieving
Q.2 Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Answer
First a cup of water is taken as a solvent in a saucer pan and heat it.. During heating, milk and tea leaves are added to the solvent as solutes. Now we get a solution.
Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer as residue. Sugar is added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea.
Q.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.
|
Substance dissolved |
|
Temperature in K |
|||
|
283 |
293 |
313 |
333 |
353 |
|
|
Potassium Sodium Potassium Ammonium |
21 36 35 24 |
32 36 35 37 |
62 36 40 41 |
106 37 46 55 |
167 37 54 66 |
(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?
Answer
Q.4 Explain the following by giving examples:
(a) Saturated solution
(b) pure substance
(c) Colloid
(d) suspension
Answer
(a)Saturated Solution: A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature. The solution cannot dissolve beyond that amount of solute at that temperature. If more solute added will settle down at the bottom of the container as a precipitate.
Suppose 300g of a solvent can dissolve a maximum of 100g of a particular solute at 250C. Then, the solution obtained by dissolving 100g of that solute in 300g of that solvent at 250C is said to be a saturated solution at 250C.
(b)Pure Substance: A pure substance is a substance consisting of a single type of particle, i.e., all constituent particles of the substance have the same chemical properties. Example- gold, silver 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 colloid is 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 medium. The particles can be seen with naked eyes. It shows the Tyndall effect. The solute particles settle down when the mixture is left undisturbed. It means suspensions are unstable. Suspensions can be separated by the method of filtration.
For example, mixtures of chalk powder and water, wheat flour and water. Example- chalk- water, paints etc.
Q.5 Classify each of the following as a homogeneous or heterogeneous mixture : soda water, wood, air, soil, vinegar, filtered tea.
Answer
Homogeneous mixture: Soda water, air, vinegar, filtered tea.
Heterogeneous mixture: Wood, soil. Air is a homogeneous mixture of different gases. If some dust or other particles are present, then air becomes a heterogeneous mixture.
Q.6 How would you confirm that a colourless liquid given to you is pure water?
Answer
Every liquid has a specific boiling point. Pure water has a boiling point of 1000C (373K) at 1 atmospheric pressure. If the given colourless liquid boils at slightly above or below 1000C, then the given liquid is not pure water. It must boil at sharp l000C, Thus by observing the boiling point, and we can confirm whether a given colourless liquid is pure water or not.
Q.7 Which of the following materials fall in the category of a ‘pure substance’?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air
Answer
Pure substances –
(a) Ice
(b) Iron
(c) Hydrochloric acid
(d) Calcium oxide
(e) Mercury
Q.8 Identify the solutions among the following mixtures:
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda Water
Answer
The following mixtures are solutions –
(b) Sea water (c) Air
(e) Soda water
Q.9 Which of the following will show ‘Tyndall effect’?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution
Answer
Milk and starch solution will show the ‘Tyndall effect’.
Q.10Classify 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
Answer
Elements-
(a) Sodium
(b)Sliver
(c)Tin
d)Silicon
Compounds
(e) Calcium Carbonate
Mixture –
(b) Soil (c) Sugar Solution
(h) Coal (i) Air
(j) Soap (m)
Blood
Q.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
Answer
The following changes are chemical changes:
(a) Growth of a plant (b)Rusting of iron
(c) Cooking of food (d) Digestion of food
(e) Burning of candle
Related Topics
RBSE Class 9 Science All Chapters Solutions
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