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Many solids can be changed into liquids. How can that be? Is it magic? NO! It's science!
We have a few small pans, a hot-plate, and an assortment of solids that we will change into liquids.
Taking turns, we will heat a piece of paraffin (wax, commonly used for sealing jars of homemade jam), a sugar cube, a square of baking chocolate, and a piece of butter, margarine, or shortening. (Be sure to use low heat on the hot-plate, because all this stuff can burn. Wax can be especially dangerous, because it can suddenly get too hot, and burst into flames.)
We put the items in pans, turn on a little heat, and what happens? What is it called?
Right! It's called MELTING.
Now, watch what the teacher can do. This is really exciting! Look at the fishing weight we have, which is made of a very heavy metal, called lead. The teacher can put it into a tin can, hold the can with pliers, and turn up the heat. That metal will actually melt! Actually, any metal can melt if there is enough heat; some metals have to be very, VERY hot before they will melt. Lead has what is called a "low melting point," which means it doesn't have to get terribly hot before it melts.
Now, we'll perform some more magic. We'll take the pans from the heat, and place them each into a larger container with ice cubes. Watch what happens!
The stuff changes back into solid. You can see, however, that the shapes of the substances are not the same as they were before they melted. When they solidify (say "so-lid-if- eye"), they take the shape of the con-tainers. I guess that in order for the substances to have the shapes they had before we melted them, they must have been melted and poured into molds.
When liquids are turned into solids, the process is called "freezing," even when it doesn't get ice cold.
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