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NOW WE'LL MAKE A THERMOMETER Your teacher will have to go to the supply place for some simple equipment. After the shopping trip, you can make a thermometer. Using a twisting motion, put a length of glass tubing about 1 foot long through a one-hole stopper. Fill a bottle or flask to the top with water, and add a drop of red coloring to make the water more visible. Force the stopper into the bottle so that the water rises into the tube about 3 inches. Mark the position of the water, then warm the bottle with your hands. Note that the colored water rises in the tube. Now cool the bottle with an ice cube or a sponge soaked in cold water, and note that the water level drops. To calibrate this instrument, place the bottle in a deep bowl filled with ice cubes. When the liquid in the tube stops descending, tie a string or slip a rubber band around the tube to mark the level of the liquid. Next, place the bottle in a pan of water, and heat it. Boil the water in the pan until the level of the colored liquid stops rising. Mark the level with another piece of string or a rubber band. The two marks represent the high and low points. A card divided into tenths and hundredths can be placed behind the tube for a scale. This instrument works like a commercial liquid thermometer -- the liquid expands when heated and contracts when cooled. Commercial liquid thermometers use alcohol or mercury instead of water, however, since these liquids respond uniformly to temperature changes and do not freeze at temperatures below 32 degrees F. Fever thermometers, which register temper- atures from 94o F. to 106o F., often have red liquid in them. Do you suppose that is alcohol? What about those new ones that you can hold just inside one's ear until it beeps? How do they work? Other types of thermometers can be compared to this one. Ask your teacher how digital thermometers work. Also ask if they do work!  Any problems with this page? Send URL to
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