Question

9.
List any 3 observations while we do this activity.
.​

Answer 1

Answer:

The following observations in an activity may suggest that a chemical reaction has taken place:

∙ Change in state

∙ Change in colour

∙ Evolution of a gas

∙ Change in temperature

(i) Calcium oxide reacts vigorously with water to produce calcium hydroxide. During this process, a large amount of heat is also evolved, which increases the temperature of the system. This confirms that a chemical reaction has taken place.

CaO(s)+H 2

O(l)→Ca(OH) 2

(aq)

ii) Also, when calcium carbonate is heated, it decomposes to form calcium oxide and carbon dioxide.

Here, evolution of the gas (carbon dioxide) confirms that a chemical reaction has taken place.

CaCO 3

→CaO+CO 2