Solution to Extended Learning 5 of Class 8 Science Chapter 4 Combustion and Flame

5. Make a model of a fire extinguisher. Place a short candle and a slightly taller candle in a small dish filled with baking soda. Place the dish at the bottom of a large bowl. Light both the candles. Then pour vinegar into the dish of baking soda. Take care. Do not pour vinegar on the candles. Observe the foaming reaction. What happens to the candles? Why? In what order?

Answer: The above experiment can be carried out as follows:

Aim: To observe what happens to the candles after vinegar is poured and make the necessary conclusions.

Materials Required: Two candles (one taller than the other), small dish, baking soda, vinegar.

Procedure:

(i) Fill the small dish with baking soda.

(ii) Place the short candle and the slightly taller candle in the small dish filled with baking soda.

(iii) Place the dish at the bottom of a large bowl.

(iv) Light both the candles.

(v) Then slowly pour vinegar into the dish of baking soda, taking care to not pour vinegar on the candles. Observe what happens and make the conclusions.

Observations:

You will observe that the shorter candle gets extinguished first and then the taller candle.

Dish containing baking soda and candle inside a bigger bowl. — **Fire Extinguisher:** As vinegar is poured into the baking soda, a foaming reaction occurs. The shorter candle is extinguished first, then the longer candle. Let us see why.

Conclusions:

We conclude that in the reaction between baking soda and vinegar carbon dioxide gas is evolved. As the carbon dioxide gas rises from the mixture it blankets the flame of the shorter candle first and then the longer candle, thereby cutting off the oxygen supply. Thus, the shorter candle gets extinguished first and then the longer candle due to lack of supporting oxygen.

“Make a model of a fire extinguisher. Place a short candle and a slightly taller candle in a small dish filled with baking soda. Place the dish at the bottom of a large bowl. Light both the candles. Then pour vinegar into the dish of baking soda. Take care. Do not pour vinegar on the candles. Observe the foaming reaction. What happens to the candles? Why? In what order?” – Solved.