A thermometer is an instrument that measures the
temperature. Temperature is measured in a scale
called Fahrenheit (by most people in the United
States) and in Celsius or Centigrade (used by
scientists and by people in many other countries).
The point where water freezes is 32 degrees Fahrenheit
(F for short) and 0 degrees Celsius (C). The point
where water boils is 212 degrees F and 100 degrees
C. If you want to know how to convert from F to
C or from C to F, see the end of this page.
Some scientific thermometers use the Kelvin scale,
where 0 Kelvin is called absolute
zero - a place where there is no movement of
any parts of matter, where substances have no
thermal energy. It's about minus 273.15 degrees C
(below 0° C) or 459.67 degrees below 0° F.
Scientists have never been able to measure
anything at absolute zero, though they have
gotten very close.
Thermometers help us know what the weather will be
like. If it will be 90°F outside, we're not
going to put on a winter coat. Or if it's below
zero, we won't be wearing shorts. Here's a way to
show how a simple thermometer works.
- Tap water
- Rubbing alcohol (do not drink this)
- Clear, narrow-necked plastic bottle (11-ounce water bottles work well)
- Food coloring
- Clear plastic drinking straw
- Modeling clay