This document contains questions and answers about mixtures and solutions. It discusses key concepts like saturated vs unsaturated solutions, solute and solvent identification, and properties of mixtures like colloids and suspensions. Examples are provided to illustrate concepts like Tyndall effect, separating mixtures using a separating funnel, and classifying mixtures as homogeneous or heterogeneous. Fifteen questions in total are asked and answered about pure substances, solutions, and properties that can be used to characterize different types of mixtures.

1. UNIT- IS MATTER AROUND US
PURE
EXTRA QUESTIONS
PART-1
BY- MISS RITIMA
APS RAKHMUTHI

2. Q.1 How can you change a saturated solution to an unsaturated solution without adding
any more solvent to it?
Answer
By heating the saturated solution, it becomes unsaturated.
Q.2 Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together.
Will it be a pure substance or a mixture? Give reasons for the same.
Answer
It is a pure substance because chemical composition of sugar crystals is same irrespective
of its source.
Q.3 Based on which factor a solution is said to be diluted, concentrated or saturated?
Answer
A solution is said to be diluted, concentrated or saturated on the basis of the amount of
solute dissolved in the solution.
Q.4 Identify solute and solvent in 'tincture of iodine'.
Answer
Iodine is the solute and alcohol is the solvent.
Q.5 What is mass per cent of a solution?
Answer
It is defined as the mass in grams of the solute present in one hundred grams of a
solution

3. Q. 6. 'Sea water can be classified as homogeneous as well as heterogeneous mixture.'
Comment.
Answer
Sea water is a mixture of salts and water which cannot be separated except by
evaporation. Therefore, sea water is considered homogeneous. Sea water also contains
mud, decayed plant, etc., other than salts and water, so it is heterogeneous also.
Q.7. Why is it not possible to distinguish particles of a solute from the solvent in solution?
Answer
A true solution is homogeneous in nature. The solute and solvent particles are very small.
They cannot be distinguished even under a microscope.
Q. 8. Explain why particles of a colloidal solution do not settle down when left
undisturbed, while in the case of a suspension they do.
Answer
Particle size in a suspension is larger than those in a colloidal solution. Also molecular
interaction in a suspension is not strong enough to keep the particles suspended and
hence they settle down.

4. Q.9. Identify colloids and true solutions from the following:
Answer
Pond water, fog, aluminium paint, vinegar and glucose solution.
True solutions are vinegar and glucose solution. Colloids are fog, aluminium paint.
Q.10. Give two examples each for: (i) Aerosol, (ii) Emulsion. In what way are they different?
Answer
(i) Aerosol: Clouds, smoke
(ii) Emulsion: Milk, face cream.
Smoke and fog both are aerosols.
Both fog and smoke have gas as the dispersion medium. The only difference is that the
dispersed phase in fog is liquid and in smoke it is a solid.

5. -Q. 11. Describe any three properties of colloid.
Answer
(i) It is a heterogenous mixture.
(ii) Size of particles is too small to be seen by naked eye.
(iii) They scatter light passing through them making its path visible.
(iv) They do not settle down when left undisturbed.
(v) They cannot be separatsed by the process of filtration.
Q.1 2. State the principle of separating two immiscible liquids by separating funnel.
Describe an activity with diagram to separate a mixture of water and kerosene oil.
Answer
Immiscible layers separate out in layers depending on their densities in separating funnel.
Activity to separate kerosene oil from water using a separating funnel:
• Pour the mixture of kerosene oil and water in separating funnel as shown in figure.
• Let it stand undisturbed for sometime so that separate layers of oil and water are
formed.
• Open the stopcock of the separating funnel and pour out the lower layer of water
carefully.
• Close the stopcock of the separating funnel as the oil reaches the stopcock.

6. Q.13. Explain Tyndall effect with example?
Ans. Tyndall Effect
If a light is passed through a medium and its path can be seen, then the substance is
said to show Tyndall effect.
Example When a beam of sunlight enters a dark room through some hole in the
window, path of light becomes visible due to scattering of light by the colloidal dust
particles present in the air of cinema hall. This shows Tyndall effect.
Q.14. If salt is added to water, is the mixture homogeneous or heterogeneous. Give
reasons for your Answer?
Ans. The mixture is homogeneous because the salt particles do not form a separate
layer and the particles cannot be separated from the water by filtration. Also every
portion of the solution is equally salty, as the solution has salt uniformly dispersed in
it.
Q.15. list important properties of mixtures.
Ans. Properties of Mixtures:
• A mixture may be homogenous or heterogeneous.
• The composition of a mixture is variable.
• A mixture does not have a definite melting point or boiling point.
• Energy is neither absorbed nor evolved during the formation of a mixture.
• The properties of mixture are the properties of its constituents.
• The constituents of mixture can be separated by simple physical methods.
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