Activity 5.5 Let us investigate (Pages 62-63) What happens to the candle flames in the two cases? Class 7

Activity 5.5 Let us investigate (Pages 62-63) Class 7

Activity 5.5 Let us investigate (Pages 62-63) Class 7

What happens to the candle flames in the two cases?

Answer:

We observe that the candle that was not covered (Fig. 5.6a) continues to burn, whereas the candle that was covered with a glass tumbler (Fig. 5.6b) stops burning after some time.

Question 1.

Why does this happen?

Answer:

The candle covered by the glass tumbler does not have a continuous supply of air, so the flame gets extinguished soon. The component of air that supports combustion is oxygen.

Question 2.

How can you test the presence of carbon dioxide gas?

Answer:

We can test the carbon dioxide gas by adding a small amount of lime water in the petri dish. We see that it turns milky.

Question 3.

What else is needed to start combustion?

Answer:

Requirements for combustion process to occur:

1. A combustible substance (fuel)
2. Oxygen
3. Heat that allows the fuel to reach its ignition temperature.