Be careful not to disturb the water. Observe where the red and blue food coloring goes. Using the red and blue pencils draw what you see happening. Click here to hear one answer. The cold water sinks while the warmer red water rises, or stays higher than the blue.
Convection is the action of warm air rising and cold air sinking.
You probably guessed that the blue water represents a cold air mass and the red water represents the warm, unstable air mass. A thunderstorm is caused by unstable air and convection plays an important part. A body of warm air is forced to rise by an approaching cold front. A strong, persistent updraft of warm moist air is formed and lifted by the approaching cold front. The air cools as it rises, condenses, and forms cumulus clouds.