Question 3

A chemical change may involve
(a) change in colour only
(b) change in temperature only
(c) evolution of gas only
(d) All of the these

Q.

The chemical reaction between quicklime and water is characterised by :
(a) evolution of hydrogen gas

(b) formation of slaked lime precipitate

(c) change in temperature of mixture

(d) change in colour of the product

Q.

Question 11
Consider the following statements:

Which of these statements are correct?

(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator.

Which of these statements are correct?
(i) All four
(ii) a and d
(iii) b and c
(iv) only d

Q. (a) What is meant by chemical reaction? Explain with the help of an example.
(b) Give one example each of a chemical reaction characterised by:
(i) evolution of a gas
(ii) change in colour
(iii) formation of a precipitate
(iv) change in temperature
(v) change in state.

Q.

Which of the following observations helps to determine whether a chemical reaction has taken place or not?

(i) Change in state.

(ii) Change in colour.

(iii) Change in shape

(iv) Evolution of gas.

(v) Change in temperature.

Q. Give an example each of a change that involves:
(a) A change in colour
(b) Evolution of a gas
(c) Production of sound [3 marks]