Are you looking for a science experiment to do with your kids at home? Then, wow your preschoolers or kindergarteners with a science experiment that teaches them how the density of water changes when it is heated. After all, who doesn’t enjoy science activities for kindergarten that only require common household items?
SUPPLIES FOR THE WATER SCIENCE EXPERIMENT
You will need an adult to supervise this activity as it involves hot water.
- Two identical wide mouthed small clear glass jars
- Food Coloring – Red and Blue
- Index or plastic card ( Old playing card can be used if it covers the mouth of the jar )
- Shallow Dish/Plate or baking pan
- Hot and Cold Water
How do you do hot and cold water density experiment?
Fill one jar with cold water and the other with hot water.
Pour blue food coloring into the cold water and red food coloring into the hot water.
Make sure both jars are completely filled with water. To avoid spills, place them in the shallow plate.
Tap the card gently on top of the hot water jar. The card should completely cover the jar’s mouth. It will aid in the formation of a seal between the water and the jar.
Pick up the hot water jar with care (you’ll need an adult for this part) and turn it completely upside-down.
If the jar is tilted but not completely turned over, the water will gush out and make a mess. So, without hesitation, flip the jar over.
You may not need to place your hand on the card because the vacuum created inside the jar keeps it on the surface.
Before attempting it with hot water, it is best to practice turning the jar upside down with an index card placed on top of it under the sink using tap water.
Place the red jar upside down on top of the blue jar. Check that the edges of both jars are perfectly aligned all around.
Allow someone to hold both jars while you slowly and patiently pull out the card from between the jars.
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DENSITY EXPERIMENT : THE SCIENCE OF Hot and Cold Water
Why does hot and cold water not mix?
Empty and clean both jars. Carry out the previous experiment, but this time turn the blue jar upside down and place it on top of the red jar. What happens next? Why does the water mix this time?
The reason for this is that when two liquids of different densities are combined, the liquid with lower density floats on top of the denser liquid.
Hot water has a lower density than cold water.
When water is heated, the water molecules begin to bounce off each other, causing them to move farther apart and thus create more space between the molecules.
Eventually, a volume of hot water contains fewer molecules and weighs less than a volume of cold water.
As a result, hot water is less dense than cold water.
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When you place the jar containing hot water on top of the jar containing cold water, the cold water does not have to rise because it is denser than the hot water and thus remains at the bottom.
When you place the jar with cold water on top of the jar with hot water, the hot water rises to the top because it is less dense, mixing with the cold water along the way and creating purple water.
FURTHER EXTENSION ON Water Density
Try the same experiment with a jar of salted water and a jar of plain water. And let us know in the comments section which one is more dense.
Check out some of these great books on science experiments that are simple and fun to do at home if you want to stir up your children’s scientific curiosity.
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Thanks for reading! We hope you enjoyed this post on hot and cold water science experiments. Be sure to check out our other posts for more fun and interesting STEM activities you can do at home with your kids. As always, if you have any questions or comments, feel free to leave them below. Happy experimenting!
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