Question

Why does a candle flame defy gravity and burn upward?

• A. Flame is weightless and is not affected by gravity.
• B. Due to convection around the flame.
• C. Due to the upward movement of colder air.
• D. All flames experience a repulsive force from the Earth.

Answer 1

The correct option is B Due to convection around the flame.

Whenever there is a fire, there is heat produced as well. Now the heat is transferred by free movement of air molecules. This process is called convection.
When you light a candle, the heat energy that is generated is transferred to the surrounding air by convection.
This increases the temperature of the surrounding air. The heat expands the air and as a result, reduces its density. The gravity pulls down the relatively colder and denser air, which displaces the hot air, and shoots the flame up. It is this hot air rushing upwards, because of the temperature difference that is created, that gives the flame a teardrop shape.