Answer the following question based on the figure given alongside. Which gas helps the candle in burning?

The oxygen gas helps the candle in burning, without oxygen substances cannot burn. It is observed that the candle extinguishes after some time. This happens because oxygen inside the glass tumbler is utilized by the candle for the burning process. When all the oxygen inside the glass tumbler gets converted into carbon dioxide, the flame goes off.

Answer the following question based on the figure given alongside. Give any one use of oxygen gas other than burning?

Oxygen makes up about 21 % of air. All living things i.e. animals, plants and humans use oxygen for respiration. During respiration, oxygen breaks down food to give carbon dioxide, water and energy. It is also used in hospitals for patients suffering from breathing problems.

Answer the following question based on the figure given alongside. Will the candle continue burning for long? Why/why not?

Oxygen is necessary for burning, without it, substances cannot burn. A lit candle needs to draw oxygen from the air to continue burning. If we limit the amount of air available, the candle's flame eventually goes out once it uses up all the oxygen. While burning, the oxygen inside the jar is converted to carbon dioxide.

Answer the following question based on the figure given alongside. What causes the water to rise up in the jar?

Oxygen gas present inside the jar is used for burning the candle. As it gets used up by the flame, there is a decrease in temperature to the initial temperature and this will help water vapour to condense. This condensation will decrease the pressure inside the jar and will help water rise in the jar.

Answer the following question based on the figure given alongside. What is the name of the main gas left in the jar?

Carbon dioxide is the main gas left in the jar. This is because by covering the candle with a jar, the supply of oxygen gets cut. And, as there is only a limited quantity of oxygen left inside the jar, the candle burns for a moment and then goes off completely. By burning, all the available oxygen is converted into carbon dioxide.