Chapter 6: Physical and Chemical Changes

Q14Written answer

Match the items of Column I with the items of Column II.

Column I	Column II
a) Large crystals	i) Turns lime water milky
b) Depositing a layer of zinc on iron.	ii) Physical change
c) Souring of milk	iii) Rust
d) Carbon dioxide	iv) Sugar candy (mishri)
e) Iron oxide	v) Chemical change
f) Dissolving common salt in water	vi) Galvanisation

Show solutionHide solution

Worked solution

Ans: The arranged table is given below:

Column I	Column II
a) Large crystals	iv) Sugar candy (mishri)
b) Depositing a layer of zinc on iron.	vi) Galvanisation
c) Souring of milk	v) Chemical change
d) Carbon dioxide	i) Turns lime water milky
e) Iron oxide	iii) Rust
f) Dissolving common salt in water	ii) Physical change

Q15Written answer

Fill in the blanks in the following statements using the words given in the box.

rusted, colourful, substance, chemical, physical, reversible, iron oxide, object

(a) Making sugar solution is a ____________ change.

(b) A physical change is generally____________.

(c) Grinding of wheat grain changes its size. It is a ____________ change.

(d) Iron benches kept in lawns and gardens get____________. It is a _________ change because a new _________ is formed.

Show solutionHide solution

Worked solution

Ans: Making sugar solution is a physical change.

Ans: A physical change is generally reversible.

Ans: Grinding wheat grain changes its size. It is a physical change.

Ans: Iron benches kept in lawns and gardens get rusted. It is a chemical change because a new substance is formed.

Q16Written answer

Classify the following processes into physical or chemical changes:

(i) Beating of aluminium metal to make aluminium foil.

(ii) Digestion of food.

(iii) Cutting of a log of wood into pieces.

(iv) Burning of crackers.

Show solutionHide solution

Worked solution

Ans:

(i) Beating of aluminium metal to make aluminium foil: Physical change.

(ii) Digestion of food: Chemical change

(iii) Cutting of a log of wood into pieces: Physical change

(iv) Burning of crackers: Chemical change

Q17Written answer

Write word equations for two chemical reactions with the help of materials given in the box.

Air, copper sulphate, iron, vinegar, iron oxide, carbon dioxide, iron sulphate, copper, lime water, water

Show solutionHide solution

Worked solution

Ans: The reactions are given below:

$Iron\; + \;Air\; + \;water\; \to \;Iron\;oxide$ and

$Copper\;sulphate\; + \;Iron \to \;Iron\;sulphate\; + \;copper\;$

Q18Written answer

Explain the following:

(a) Lime water turns milky on passing carbon dioxide gas into it.

(b) Bubbles are produced when acetic acid is added to a solution of sodium hydrogen carbonate.

Show solutionHide solution

Worked solution

Ans: When carbon dioxide gas is introduced into lime water, a white precipitate of 'calcium carbonate’ is formed. This comment elicited the following response:

Calcium hydroxide + Carbon dioxide → Calcium carbonate + water

Ans: The chemical interaction between 'acetic acid' and' sodium hydrogen carbonate' produces 'carbon dioxide.' This comment elicited the following response:

Sodium hydrogen carbonate + Acetic acid→ Sodium carbonate + water + Carbon dioxide

My Cart

Your Cart 0

Short Answer Questions