Question

Perform an activity to show that a chemical reaction has taken place (change in state and change in colour).​

Answer 1

Answer:

The following observations in an activity may suggest that a chemical reaction has taken places.

∙ 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

​

Explanation:

Answer 2

Activity:

Perform an activity to show that a chemical reaction has taken place (change in state and change in colour).

Materials required:

Magnesium ribbon, pair of tongs burner ,watch glass.

Procedure:

1. Take a piece of Mg Ribbon about 2 cm long.

2. Rub it clean with the help of a Sandpaper.

3. Hold it with a pair of tongs as shown in figure above.

4. Burn it using a burner (or a spirit lamp) keeping it safely away from your eyes .Collect the matter falling from the pair of tongs on a watch glass.

5. You are observed that Mg Ribbon burns with a dazzling light and produces a white ash consisting of magnesium oxide.

Result:

• This activity illustrates that a chemical reaction has taken place. There has been a change of state and change of colour in this activity. Silvery Mg Ribbon has changed into powdery white MgO.

${ \bold { \underline{\large{Note : - }}}} \:$ Figure of this activity is attached above.