EVENTS
CONVENT HIGH SCHOOL
19/08/2021 CLASS-9 SESSION2021-22(SLOT-1)
SCIENCE
Chapter-2
IS MATTER AROUND IS PURE?
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Question 1. What is meant by a
substance?
Answer: A pure substance consists of
a single type of particles.
Answer:
Question 1. Name the technique to separate
(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.
Answer: (i) Centrifugation,
(ii) Evaporation,
(iii) Sublimation.
Question 2. What type of mixtures
are separated by the technique of crystallisation?
Answer: Crystallisation technique is
used to purify solid with some impurities in it. Example: Salt from sea-water.
Question 3. Classify the following as chemical or physical changes:
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.
Answer:
Question 4. Try segregating the things around you as pure substances or mixtures
Answer: Pure substances—Water,
bread, sugar and gold.
Mixtures—Steel, plastic, paper, talc,
milk and air.
TEXT BOOK ANSWER THE FOLLOWING QUESTIONS:-
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 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.
Answer: (a) Evaporation
(b) Sublimation
(c) Filtration
(d) Chromatography
(e) Centrifugation
(f) Separating funnel
(g) Filtration
(h) Magnetic separation
(i) Winnowing/ sedimentation
(j) Decantation and filtration
Question 2. Write the steps you
would use for making tea. Use the words, solution, solvent, solute, dissolve,
soluble, insoluble, filtrate and residue.
Answer: 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.
Question 3. 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?
Answer: A mixture of kerosene and
petrol which are miscible with each other can be separated by distillation.
Method
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.
Question 4. Explain the following
giving examples:
(a) Saturated solution
(b) Pure substance
(c) Colloid
(d) Suspension
Answer: (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.
Question 5. Classify each of the
following as a homogeneous or heterogeneous mixture: soda water, wood, air.
soil, vinegar, filtered tea.
Answer: Homogeneous: Soda water,
vinegar, filtered tea.
Heterogeneous: Wood, air, soil.
Question 6. How would, you confirm
that a colourless liquid given to you is pure water?
Answer: 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.
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) Back (h) Wood (i) Air.
Answer: Pure substances are: Ice,
iron, hydrochloric acid, calcium oxide and mercury.
Question 8. Identify the solutions
among the following mixtures.
(a) Soil (b) Sea water
(c) Air (d) Coal
(e) Soda water.
Answer: Solutions are: Sea water
soda water and air.
Question 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.
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 – Compounds –
Mixtures
Sodium – Calcium carbonate – Sugar solution
Silver – Methane – Soil
Tin – Carbon dioxide – Coal
Silicon – Soap – Air ,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 are:
(a) Growth of a plant (b) Rusting of
iron
(c) Cooking of food (d) Digestion of
food
(e) Burning of a candle
