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When water is heated, its molecules move more rapidly as the heat increases. Because the molecules are jumping around, and evaporating into the air more quickly, the hot water is less dense. Cold water has slower-moving molecules that tend to sink because of their density. Try this cool experiment to learn more about water and its properties.

• 2 Identical jars with wide mouths that fit together perfectly (baby food jars are ideal)
• Hot water
• Cold water
• Food coloring
• Index cards or squares of waxed paper
• Scissors
• A large, shallow baking pan

1. You might need a grownup’s help– always be careful with hot water!
2. First, fill up one of the jars with very hot water. Add a drop of red food coloring. Now, fill the other jar with cold tap water. Add a drop of blue food coloring. Does the temperature of the water affect the food coloring?
3. Next, cut your index card until it becomes a square with 3 inches on each side.
4. Carefully add more cold water to the blue colored jar so that the water bulges a bit over the edge. Now place the index card carefully onto the top of the blue jar. Very gently tap the card with your finger so that it forms a seal with the card.
5. Now for the tricky part– turn the jar with the blue water over very quickly. It should not spill if you turn it over perfectly fast. Put the upside-down blue jar on the mouth of the red jar.
6. Ask someone to help you by holding the jars as you very slowly pull out the index card. What happens to the blue water? What happens to the red water?
7. Empty the jars and rinse them out. Now, repeat all of the beginning steps, but put the blue water jar on the bottom, and the red water jar on the top. Does something different happen? What color is the water?