Question

Write any two observations in an activity which may suggest that a chemical reaction has taken

place. Give an example to support your answer​

Answer 1

1. Evolution of gases

2. Formation of precipitate

3. change In state

Answer 2

i. In an activity, when any of the following occurs, it suggests that a chemical reaction has taken place:

a. change in state

b. change in colour

c. change in temperature

d. evolution of gas

ii. In an activity, change in state and evolution of gas indicate that a chemical reaction has taken place:

eg. Magnesium reacts with hydrochloric acid to give aqueous magnesium chloride and hydrogen gas.

iii. In an activity, change in state and change in temperature indicate that a chemical reaction has taken place:

eg. Calcium oxide reacts vigorously with water to produce slaked lime (calcium hydroxide) releasing a large amount of heat.

CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat