AP 9th Class Physical Science 2nd Lesson Questions and Answers Is Matter Around Us Pure
9th Class Physics 2nd Lesson Is Matter Around Us Pure Questions and Answers (Exercise)
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 chortic.
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.
Answer:
Separation techniques :
a) Evaporation
b) Sublimation
c) Filtration
d) Chromatography
e) Churning (or) Centrifugation
f) Separating funnel
g) Filtration
h) Magnetic separation
i) Winnowing
j) Sedementation / decantation.
Question 2.
Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Answer:
Steps for making tea :
Take water as solvent and boil it a few minutes.
Add solutes, i.e., milk, tea leaves, sugar. Now, again boil the solution for few minutes.
Sugar is soluble in water thus it will be dissolve.
Colour of tea leaves goes into solution as filtrate. The remaining tea leaves being insoluble remains as residue.
Now, filter the solution. Collect the filtrate in cup.
The insoluble tea leaves will be left behind as residue.
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 ?
Answer:
Solubility of potassium nitrate at 313 K = 62/100
100 g of water contains potassium nitrate =62 g
50 g of water contains potassium = 62100 × 50 = 31g
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.
Answer:
As solution cools, potassium chloride gets crystallized or precipitated. Because at 353 K solubility of potassium chloride is 54 g, 100 g of water. Where at room temperature it is 35 g. So, excess of potassium chloride dissolved gets precipitated.
AP 9th Class Physics 2nd Lesson Questions and Answers Is Matter Around Us Pure
c) Find the solubility of each salt at 293 K . Which salt has the highest solubility at this temperature?
Answer:
Potassium nitrate = 32 g
Sodium chloride = 36 g
Potassium chloride = 35 g
Ammonium chloride = 37 g
Ammonium chloride has the highest solubility of 37 g at 293 k
d) What is the effect of change of temperature on the solubility of a salt ?
Answer:
The rate of solubility increases with the increase of temperature.
Question 4.
Explain the following giving examples.
a) Saturated solution
b) Pure substance
c) Colloid
d) Suspension
Answer:
a) Saturated solution : A solution in which the maximum possible amount of a solute is dissolved at a given temperature.
Ex:
Take 50 ml of water in a cup.
Add one spoon of sugar to the cup and stir still it dissolves.
Keep on adding sugar to the water in the cup and stir till no more sugar can be dissolved.
The solution so formed is a saturated solution.
b) Pure substance : A single form of a substance (or) matter is called pure substance.
Ex : Elements & compounds.
c) Colloid : It is a heterogeneous mixture which has intermediate properties between solution & suspension. Ex : Smoke, starch solution, ink, butter, cheese.
d) Suspension : A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout. Ex : Muddy water, Syrups, Chalk powder, mixed with water.
Question 5.
Classify each of the following as a homogeneous or heterogeneous mixture.
soda water, wood, air, soil, vinegar, fitered tea
Answer:
Soda water :
Heterogeneous : When bottle if it opened.
Homogeneous : When a bottle if it is not opened.
Wood : Heterogeneous
Air : Homogeneous
Soll : Heterogeneous
Vinegar : Homogeneous
Filtered tea : Homogeneous
Question 6.
How would you confirm that a colourless liquid given to you is pure water ?
Answer:
Every liquid hasia characteristic boiling point at 1 atmospheric pressure. If the given odourless liquid boils at exactly 373 K at 1 atmospheric pressure, then it confirms that the given liquid is pure water. Otherwise, it is contaminated.
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
Answer:
Pure substance :
a) Ice
c) Iron
d) Hydrochloric Acid
e) Calcium oxide
f) Mercury.
Question 8.
Identify the solutions among the following mixtures.
a) Soil
b) Sea water
c) Air
d) Coal
e) Soda water
Answer:
b) Sea water
c) Air
e) 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
Answer:
b) Milk
d) Starch solution show tyndall effect as they are colloids.
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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
Answer:
Elements
a) Sodium
d) Silver
f) Tin
g) Silicon
Compounds :
e) Calcium carbonate
k) Methane
l) Carbondioxide
Mixtures
b) Soil
c) Sugar solution
h) Coal
i) Air
j) Soap
m) Blood
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
Answer:
Chemical changes :
a) Growth of a plant
b) Rusting of iron
d) Cooking of food
e) Digestion of food
g) Burning of a candle
12. A startup company launches three new products:
1. A room freshener spray
2. A medicinal antacid suspension (like milk of magnesia)
3.A coloured decorative glass panel
Which of the following correctly identifies the type of colloid in each product?
A) Spray - Foam; Antacid - Emulsion; Glass - Gel
B) Spray - Aerosol; Antacid - Sol; Glass - Solid sol
C) Spray - Emulsion; Antacid - Gel; Glass - Aerosol
D) Spray - Sol; Antacid - Foam; Glass - Emulsion
✅ Correct Answer: B) Spray – Aerosol; Antacid – Sol; Glass – Solid sol
Explanation:
1. Room freshener spray → Aerosol
Liquid droplets are dispersed in a gas (air).
2. Milk of magnesia (antacid suspension) → Sol
Solid particles (Mg(OH)₂) are dispersed in a liquid.
3. Coloured decorative glass panel → Solid sol
Solid particles are dispersed in a solid medium (glass).
๐ Answer: B) Spray – Aerosol; Antacid – Sol; Glass – Solid sol
