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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
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
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
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