See Convection Currents

Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Fluids and Surface Tension, Heat, Plate Tectonics, Weather and Climate

Alternative titles: Hot and Cold Water Convection

Summary

A small container of hot, colored water is placed in a larger container of cold water. The warm water rises and circulates through the cold water, creating visible convection currents that illustrate heat transfer and density differences.

Procedure

Fill a tall glass or jar with cold water.
In a smaller cup, add hot (not boiling) water and mix in a few drops of food coloring.
Carefully place the small cup inside the larger container of cold water.
Observe how the warm, colored water rises upward, spreads, cools, and eventually sinks, creating convection currents.

Links

Try This: See Convection Currents with Water and Food Coloring - Science Museum OK (similar concept to procedure):

📄 Convection Currents Made Easy - Science Sparks: https://www.science-sparks.com/convection-currents-made-easy/

Variations

Repeat the activity using cold water inside cold water and observe how little movement occurs.
Use two food colors (one for hot, one for cold) to compare movements of warm and cool water.
Try heating water at the bottom of a pan and sprinkle in food coloring to see convection cells form directly.
Test with different container shapes (tall vs. wide) to see if convection patterns change.
Explain how this relates to convection currents in the Earth's mantle.

Safety Precautions

Use hot but not boiling water to avoid burns.
Handle glass containers carefully to avoid spills and breakage.
Have adult supervision when working with heated water.

Questions to Consider

Why does the hot water rise? (It expands, becomes less dense, and floats above cooler water.)
Why does the cooler water sink? (It is denser and moves down to replace the rising warm water.)
What eventually happens to the hot and cold water? (They mix until all the water is the same temperature.)
Where do we see convection currents in everyday life? (In weather systems, radiators, air conditioners, and hot air balloons.)
How is convection different from conduction and radiation? (Convection involves moving particles; conduction transfers energy by contact; radiation transfers heat via waves.)