Is Matter Around Us Pure: (Chapter-2)
5.
THE
FUNDAMENTAL UNIT OF LIFE
6.
TISSUES
7.
MOTION
9.
GRAVITATION
10.
WORK
AND ENERGY
11.
SOUND
12.
IMPROVEMENT
IN FOOD RESOURCES
Science Solution
Access to NCERT Class 9 Chapter-2, Is Matter Around Us Pure:
NCERT Textbook Questions
Solved for Class 9 Science Page-wise.
Topics of Is Matter Around Us Pure:
1.
Is Matter Around Us
Pure
2.
What is a Mixture?
3.
What is a Solution?
4.
Separating the
Components of a Mixture
5.
Physical and Chemical
Changes
6.
What are the Types of
Pure Substances?
These solutions are
part of NCERT
Solutions for Class 9 Science. Here we have given Class 9 NCERT Science Textbook Solutions
for Chapter 2 Is Matter Around Us Pure.
IN-TEXT QUESTIONS SOLVED
NCERT Textbook for Class
9 Science – Page 15
Question 1. What is meant by a substance?
Answer: A pure
substance consists of a
single type of particles.
Question 2. List the
points of differences between homogeneous and heterogeneous mixtures.
Answer:
|
Homogeneous Misture |
Non-Homogeneous Mixture |
|
·
It has a uniform composition ·
No visible boundaries of separation ·
They consist of only one phase. Example- Sugar +Water -> sugar
solution |
·
It does not consist of uniform composition ·
Show visible boundaries of separation. ·
They consist of more than one phase. Example- Sygar + Sand |
Question 1. Differentiate between homogeneous and heterogeneous mixtures
with examples.
Answer:
|
Homogeneous Mixture |
Non-Homogeneous Mixture |
|
1.
It has a uniform composition 2.
No visible boundaries of separation 3.
They consist of only one phase. Example- Sugar +Water -> sugar
solution |
It does not consist
of a uniform composition Show visible
boundaries of separation. They consist of more
than one phase. Example- Sygar + Sand |
Question 2. How are
sol, solution and suspension different from each other?
Answer:
|
Sol.(Colloid) |
Solution |
Suspension |
|
1.
The size of the solute particle is between 1 nCm to 100nm . 2.
it is stable 3.
it scatters a beam of light. 4.
4. Solute particles pass through filter paper. |
Size of solute
particles less than 1 nm (10-9 m) stable. It is Stable It does not scatter
of light. Solute particles
pass through the filter paper.
|
Size of solute
particles is more than 100 mm. Unstable Scatters a beam of
light. Solute particles do
not pass through the filter paper. |
Question 3. 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 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
Concentration = Mass
of Solute / Mass of Solution x 100.
= 36/136 x 100 =
26.47%
Question 1. How will
you separate a mixture containing kerosene and petrol (the 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
·
Take a mixture in a
distillation flask.
·
Fit it with a
thermometer.
·
Arrange the apparatus
as shown in the figure.
·
Heat the mixture
slowly.
·
Petrol vaporizes 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 2. 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 3. What types
of mixtures are separated by the technique of crystallization?
Answer: The crystallization technique is used to purify solid with some
impurities in it. Example: Salt from seawater.
Question 2. 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.
Answer:
Question 3. 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.
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. 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?
(b) Pragya makes a saturated solution of potassium chloride in water at 353
K and leaves the solution to coo! at room temperature. What would she observe
us 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:
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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, and filtered tea.
Answer: Homogeneous: Soda water, vinegar, filtered tea.
Heterogeneous: Wood, air, soil.
Question 6. How would,
you confirm that a colorless liquid given to you is pure water?
Answer: By finding the boiling point of a given colorless 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
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