Gases (and many liquids) have low thermal conductivity. However, energy can be transported through a fluid (liquid or gas) by convection currents.

The temperature of the water near the flame increases. This water expands and so its density is less than the water surrounding it. The higher temperature water therefore "floats" upwards transferring energy through the liquid.

A similar situation exists when a room is heated by a (badly named!) "radiator". Convection currents in air can be seen if a source of smoke is held near a room heater.

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