When hot air comes in contact with cold air, the phenomenon of convection occurs. Let's break down what happens in detail:

1. Convection:
When hot air comes in contact with cold air, the hot air rises while the cold air sinks. This is due to the difference in density between the two air masses. Hot air is less dense than cold air, so it tends to rise, creating a convection current.

2. Mixing of Air Masses:
As the hot air rises and the cold air sinks, they begin to mix together. This mixing results in the temperature of the air equalizing, creating a more uniform temperature throughout the area where the two air masses meet.

3. Formation of Clouds:
When hot and cold air masses meet, it can lead to the formation of clouds. As the warm air rises and cools, water vapor in the air condenses to form clouds. This can lead to the development of precipitation if the conditions are right.

4. Weather Changes:
The interaction between hot and cold air masses can lead to changes in weather patterns. Cold fronts, warm fronts, and other weather systems can develop when these air masses collide, leading to changes in temperature, humidity, and precipitation in the area.

In conclusion, when hot air comes in contact with cold air, it leads to convection, mixing of air masses, cloud formation, and potential weather changes. This interaction is a key factor in shaping our weather patterns and can have significant impacts on our daily lives.