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Weekend Science Fun: Hot and Cold Water

Want to have some more fun in the sink or bathtub? Let’s take a look at how hot and cold water act when they are together. Note:  always watch children around water.

You will need:

  • A plastic test tube with a cork or narrow plastic spice jar (empty) with a cap
  • Food coloring (helps you to see the results)
  • Ice cubes (optional:  colored with food coloring)

Fill a tub or sink with cold water. With an adult’s help, fill the plastic container with hot tap water and then add a drop or two of food coloring. Plug the test tube or cover the jar. Sink the container of hot water to the bottom. Gently open the lid, without disturbing the surrounding water too much. What happens?

Now, do the reverse. Fill the sink with pretty warm water, but not so hot that you will get burned when you put your hand in. Put cold water into the container and add food coloring. Stopper it up and then sink it to the bottom. What do you think will happen when you release the water? Gently release the water. What happens?

If you aren't going to do the experiment, then you can find out what happens when you put dyed cold water into a bath of warm water by watching this video (cat is optional :-).

Now, take a look at an unusual property of water. What happens when you put cold water in the form of ice into a sink of warm water? Does it float before it melts? Try freezing some ice cubes with food coloring in them to see what happens to the melt water.

When water freezes into ice, the molecules actually push away from each other a bit, making water have the unusual property of being less dense at certain cold temperatures.

Take a look at a frozen lake, puddle or pond. Because the ice freezes at the top rather than the bottom of a body of water, living things can stay underwater even in the winter. Cool!

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