Whcih matter is most likely to transfer heat by convention , solid, liquid, gas, plasma ?

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?

Is this correct if not can u correct me

Which of the following statements are incorrect?