(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water

Answer

The following mixtures are solutions:
(b) Sea water
(c) Air
(e) Soda water

(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution

Answer

Tyndall effect is shown by colloidal solution. Here milk and starch solution are colloids therefore milk and starch solution will show Tyndall effect.

(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: Sodium, Silver, Tin and Silicon.

Compounds: Calcium carbonate, Methane and carbon dioxide.

Mixtures: Soil, Sugar, Coal, Air, Soap and Blood.

(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron fillings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of candle

Answer

The following changes are chemical changes:
(a) Growth of a plant
(b) Rusting of iron
(d) Cooking of food
(e) Digestion of food

(g) Burning of candle

1. Which of the following statements are true for pure substances?
(i) Pure substances contain only one kind of particles
(ii) Pure substances may be compounds or mixtures
(iii) Pure substances have the same composition throughout
(iv) Pure substances can be exemplified by all elements other than nickel
(a) (i) and (ii)
(b) (i) and (iii)
(c) (iii) and (iv)
(d) (ii) and (iii)
Ans. (b) (i) and (iii)
Explanation: Mixture is not a pure substance, hence option (iii) is ruled out. Nickel is an element and hence pure substance; so, option (iv) is incorrect.

2. Rusting of an article made up of iron is called
(a) corrosion and it is a physical as well as chemical change
(b) dissolution and it is a physical change
(c) corrosion and it is a chemical change
(d) dissolution and it is a chemical change
Ans. (c) corrosion and it is a chemical change
Explanation: Rusting of iron is a chemical change and it leads to corrosion.

3. A mixture of sulphur and carbon disulphide is
(a) heterogeneous and shows Tyndall effect
(b) homogeneous and shows Tyndall effect
(c) heterogeneous and does not show Tyndall effect
(d) homogeneous and does not show Tyndall effect
Ans. (d) homogeneous and does not show Tyndall effect
Explanation: Solution is a homogenous mixture and does not show Tyndall effect. Colloid and suspension are heterogeneous mixtures and show Tyndall effect. Mixture of Sulphur and carbon disulphide is a solution.

4. Tincture of iodine has antiseptic properties. This solution is made by dissolving
(a) iodine in potassium iodide
(b) iodine in vaseline
(c) iodine in water
(d) iodine in alcohol
Ans. (d) iodine in alcohol

5. Which of the following are homogeneous in nature?
(i) ice (ii) wood (iii) soil (iv) air
(a) (i) and (iii) 
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (iii) and (iv)
Ans. (c) (i) and (iv)
Explanation: Soil is a heterogeneous mixture and wood too has heterogenous composition.

6. Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
(a) (i), (ii) and (iii)
(b) (i), (ii) and (iv)
(c) (i), (iii) and (iv)
(d) (ii), (iii) and (iv)
Ans. (c) (i), (iii) and (iv)
Explanation: A new substance is formed only in case of rusting of iron. In all other cases, no new substance is formed and hence they are physical changes.

7. Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Ans. (a) (i) and (ii)
Explanation: Burning and decay result in formation of new substances and they cannot be reversed. Hence, these are chemical changes.

8. Two substances, A and B were made to react to form a third substance, A2B according to the following reaction
2A + B →A2B
Which of the following statements concerning this reaction are incorrect?
(i) The product A2B shows the properties of substances A and B
(ii) The product will always have a fixed composition
(iii) The product so formed cannot be classified as a compound
(iv) The product so formed is an element
(a) (i), (ii) and (iii),
(b) (ii), (iii) and (iv)
(c) (i), (iii) and (iv)
(d) (ii), (iii) and (iv) 
Ans. (c) (i), (iii) and (iv)

9. Two chemical species X and Y combine together to form a product P which contains both X and Y
X + Y →P
X and Y cannot be broken down into simpler substances by simple chemical reactions.
Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
(a) (i), (ii) and (iii),
(b) (i), (ii) and (iv)
(c) (ii), (iii) and (iv)
(d) (i), (iii) and (iv)

Ans. (d) (i), (iii) and (iv) 
 

(a) Mercury and water
Ans. Separation by using separating funnel
(b) Potassium chloride and ammonium chloride
Ans. Sublimation
(c) Common salt, water and sand
Ans. Filtration followed by evaporation
or
Centrifugation followed by evaporation/distillation
(d) Kerosene oil, water and salt
Ans. Separation by using separating funnel to separate kerosene oil followed by
evaporation or distillation. 

Ans. The tube (a) will be more affective as a condenser. Presence of marbles increases surface area. This allows more time for condensation and hence it would be more effective than the column without marbles

Crystallization