Air has mass and density. Yes, cold air is heavier than warm
air. Cold air sinks because it is denser compared to warm air. On the other hand, warm air rises because it
is lighter.
When the air is hot or warm, its molecules are much further
when it’s cold, its molecules are slightly packed closer which is why it moves
slower.
The best association to this is the hot air balloon. Hot air balloons fly because they are filled
with hot air. Hot air is lighter than the cold air outside because when it is
heated up, it expands making it lighter.
