Convection of heat

Today we did a simple experiment to show convection currents.   Convection is the movement of heat in a fluid, which can be a liquid or a gas, but not a solid.

Examples of convection currents:

  • in weather, when warm air and cold air meet – warm air rises, cool air falls.
  • in cooking liquids such as soup – soup on the bottom of the pan gets warm and rises, and at the top cooler soup falls

In order to see this movement of heat, you can do this simple experiment.

Note: Adult help needed

Materials –

2 glass bottles

hot tap water

cold tap water

food coloring

Piece of thin cardboard

Dish or tray in case of spills


1.  Pour hot tap water into one of the glass bottles

2. Pour cold tap water into the other glass bottle

3.  Add food coloring.  We added food coloring to only one bottle, the hot water, but Steve Spangler Science shows a video of this experiment using 2 colors.


3.  Place the cardboard over the mouth of the bottle of cold water, carefully flip over while holding the card onto the bottle of warm water.

4.  Slowly pull the card out from between the bottles.


5. Observe.  The hot water rises into the bottle containing the cold water.

What is happening?
Heated water is less dense than cold water, and therefore the warm water rises to the top while the cold water sinks to the bottom.

You can read more about heat energy and convection currents here by reading The Energy Story at Energy Quest an interactive educational website for kids sponsored by the California Energy Commission.

This entry was posted in Density, Fun with color, Heat energy, Interactive Science Links, Physics. Bookmark the permalink.

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