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HOW DO HEAT
AND COLD AFFECT LIQUIDS?
Today, we're going to pretend that we are chemists, because we will be using some special equipment. These four bottles don't look very special, do they? They aren't. Take a look at the things we will fit into the tops of the bottles. These are special. They are called one-hole rubber stoppers. A stopper with a hole in it won't stop very much, will it? We could pour the liquids out through the holes!
Before we put the stoppers into the bottles, we will fill each of the four bottles. Of course, each bottle will have a different liquid, and we will make lists of the bottle numbers and the liquids inside them. We can use water, milk, dishwashing soap, and cooking oil.
Now, we fit the stoppers into the bottles, and we will put a 12-inch length of glass tubing into each stopper, pushing the tubing down through the hole, into the liquid. (This glass tubing is special equipment, also.) Do you see how the liquids rise up into the tubes, a little way past the top of the stopper? With an eye-dropper (or medicine dropper), we will put a little more of each liquid into the glass tubing so that we can see it better. Be sure the amounts added are equal. With a blue felt pen, we can put a small mark exactly at the top of the liquid in the tube of each bottle.
Very carefully, we will put the bottles into a pot with water in the bottom, and put the pot onto a hot-plate so we can heat the water in the pot. Watch the tubes, now, as the water in the pot gets warmer and warmer. What is happening? The liquids are rising in the tubes, aren't they? Let's use a red felt pen to mark the top of the liquid in each tube now, and see how much higher the liquids are. Did all the liquids rise the same amount?
We can turn off the hot plate, and let the pot cool to room temperature. See if the liquids have returned to the first mark on the tube.
Next, we will put the bottles into a bowl of ice cubes. Watch the liquids in the tubes. The liquids are going down now, even below the first mark. What on earth is happening here?
It looks as though liquids expand (get larger) with heat, and contract (get smaller) with cold. Do you suppose that is the reason that ice cubes are a little smaller than we thought they would be when we filled the ice cube trays? Could it be that bottled liquids always have a little space at the top of the bottle because the liquids would expand if they were heated by being left in the sun for awhile?
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