AP 9th Class Physics 2nd Lesson Questions and Answers Is Matter Around Us Pure

AP State Board new syllabus AP Board Solutions Class 9 Physics 2nd Lesson Is Matter Around Us Pure Questions and Answers.

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).

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 313 K ?
Answer:
Solubility of potassium nitrate at 313 K = \(\frac{62}{100}\)
100 g of water contains potassium nitrate =62 g
50 g of water contains potassium = \(\frac{62}{100}\) × 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.

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.

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

9th Class PS 2nd Lesson Questions and Answers (InText)

Question 1.
What is meant by a substance?
Answer:
Pure substances consist of a single type of particles only. Ex : Gold, Salt, Hydrogen.

Question 2.
List the points of differences between homogeneous and heterogeneous mixtures.
Answer:
Homogeneous mixture :

• Components are equally distributed throughout the mixture.
• We cannot see the particles separately.
• We cannot separate components by simple physical methods.

Heterogeneous mixture :

• Components are unequally distributed throughout the mixture.
• We can see the particles separately.
• We can separate components by simple physical methods.

Question 3.
Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer:

Homogeneous	Heterogeneous
1) Composition of homogeneous mixture is same throughout.	1) Composition of heterogeneous mixture is not same throughout.
2) No distinct boundaries.	2) They have distinct boundaries.
3) It consist only one phase.	3) It consist of two (or) more phases.
4) Components of homogeneous mixture are separable by physical methods.	4) Components of heterogeneous mixture are separable by physical methods.
5) They are stable.	5) They are may be stable (or) unstable.
6) Ex : Salt solution.	6) Ex : Oil & water.

Question 4.
How are sol, solution and suspension different from each other?
Answer:

Sol	Solution	Suspension
1) Heterogeneous	Homogeneous	Heterogeneous
2) Particles can’t be seen	Particles can’t be seen	Particles can be seen
3) Translucent (or) opaque	Transparent	Translucent
4) Particles of the size of 10-7cm to 10-5cm	Particles of the size 10-9 cm	Particles of the size 10-5 cm
5) They show tyndall effect	They don’t show tyndall effect	They show tyndall effect
6) They are stable Ex: Jelly	They are stable Ex: Sugar solution	They are not stable Ex : Chalk – water

Question 5.
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.
Answer:
Mass of the solute (Sodium chloride solution) = 36 g
Mass of solvent (water) =100 g
Mass of solution = Mass of solute + mass of solvent = 36+100=136 g
Concentration of sodium chloride solution

Question 6.
Classify the following as chemical or physical changes :
a) cutting of trees,
b) melting of butter in a pan,
c) rusting of almirah,
d) boiling of water to form steam,
e) passing of electric current, through water and the water breaking down into hydrogen and oxygen gases,
f) dissolving common salt in water,
g) making a fruit salad with raw fruits and
h) burning of paper and wood.
Answer:
a) Physical change
b) Physical change
c) Chemical change
d) Physical change
e) Chemical change
f) Physical change
g) Physical change
h) Chemical change

Question 7.
Try segregating the things around you as pure substances or mixtures.
Answer:
Pure substances : Water, Gold (24 Carat), Salt, Sugar
Mixtures : Milk, wood, cool – drinks

Examples:

Question 1.
A solution contains 40 g of common salt in 320 g of water. Calculate the concentration in terms of mass by mass percentage of the solution.
Answer:
Mass of solute (salt) =40 g
Mass of solvent (water) = 320 g
We know, Mass of solution = Mass of solute + Mass of solvent
=40 g+320g = 360g
Mass percentage of solution =\(\frac{\text { Mass of solute }}{\text { Mass of solution }}\) × 100
\(\frac{40}{360}\)× 100 = 11.1 %

9th Class Physical Science Chapter 2 Questions and Answers (Lab Activities)

(Page No. 28) Activity 2.1

1. Procedure :

• Let us divide the class into groups A, B, C and D.
• Group A takes a beaker containing 50 ml of water and one spatula full of copper sulphate powder. Group B takes 50 ml of water and two spatula full of copper sulphate powder in a beaker.
• Groups C and D can take different amounts of copper sulphate and potassium permanganate or common salt (sodium chloride) and mix the given components to form a mixture.
• Report the observations on the uniformity in colour and texture.

Observations :
1. Groups A and B have obtained a mixture which has a uniform composition throughout. Such mixtures are called homogeneous mixtures or solutions.

Some other examples of such mixtures are :

• salt dissolved in water and
• sugar dissolved in water.

2. Compare the colour of the solutions of the two groups. Though both the groups have obtained copper sulphate solution but the intensity of colour of the solutions is different. This shows that a homogeneous mixture can have a variable composition.

3. Groups C and D have obtained mixtures, which contain physically distinct parts and have non-uniform compositions. Such mixtures are called heterogeneous mixtures. Mixtures of sodium chloride and iron filings; salt and sulphur and oil and water are examples of heterogeneous mixtures.

(Page No. 30) Activity 2.2

2. Procedure :

1. Let us again divide the class into four groups – A, B, C and D.

2. Distribute the following samples to each group:

• Few crystals of copper sulphate to group A.
• One spatula full of copper sulphate to group B.
• Chalk powder or wheat flour to group C.
• Few drops of milk or ink to group D.

3. Each group should add the given sample in water and stir properly using a glass rod.
– Are the particles in the mixture visible?
Answer:
Particles of mixture are only visible in group – C.

4). Direct a beam of light from a torch through the beaker containing the mixture and observe from the front.
– Was the path of the beam of light visible?
Answer:
The path of beam of light only visible in groups C&D.

5) Leave the mixtures undisturbed for a few minutes (and set up the filtration apparatus in the meantime).
– Is the mixture stable or do the particles begin to settle after some time?
Answer:
The particles of matter settle down in group – C.

6) Filter the mixture.
– Is there any residue on the filter paper?
Answer:
Residue on filter paper left in group – D.

Observations :

• Groups A and B have got a solution.
• Group C has got a suspension.
• Group D has got a colloidal solution.

(Page No. 32) Activity 2.3

3. Procedure :

• Take approximately 50 ml of water each in two separate beakers.
• Add salt in one beaker and sugar or barium chloride in the second beaker with continuous stirring.
• When no more solute can be dissolved, heat the contents of the beaker to raise the temperature by about 5°C
• Start adding the solute again.

Observation :
– Is the amount of salt and sugar or barium chloride, that can be dissolved in water at a given temperature, the same ?
Answer:
The quantity of salt, sugar and barium chloride that can be dissolved in water at a given temperature is not the same.

(Page No. 40) Activity 2.4

4. Procedure :

• Divide the class into two groups. Give 5 g of iron filings and 3 g of sulphur powder in a china dish to both the groups.
• Group I: Mix and crush iron filings and sulphur powder.
• Group II : Mix and crush iron filings and sulphur powder. Heat this mixture strongly till red hot. Remove from flame and let the mixture cool.
• Groups I and II : Check for magnetism in the material obtained. Bring a magnet near the material and check if the material is attracted towards the magnet.
• Compare the texture and colour of the material obtained by the groups.
• Add carbon disulphide to one part of the material obtained. Stir well and filter.
• Add dilute sulphuric acid or dilute hydrochloric acid to the other part of the material obtained.
• Perform all the above steps with both the elements (iron and sulphur) separately.

Observations :
1. Did the material obtained by the two groups look the same ?
Answer: The mixtures obtained in Gr – I and Gr – II appear different.

2. Which group has obtained a material with magnetic properties ?
Answer: Group – I has magnetic properties due to presence of iron.

3. Can we separate the components of the material obtained?
Answer: Gr – I can be separated by using magnetic separation.

4. On adding dilute sulphuric acid or dilute hydrochloric acid, did both the groups obtain a gas? Did the gas in both the cases smell the same or different?
Answer:
In Group – I- Hydrogen gas gets released which is colourless and odourless.
In Group – II H₂S (Hydrogen Sulphide) gas gets released which is colouriess and gives rotten egg smell.