Temperature is a measure of the degrees of hottness of something. The United States uses the Fahrenheitscale for measuring temperature. (Pure water will freeze at 32°F at sea level, it will boil at 212°F.) Most nations use Celsiusor centigrade. This system is a metric system where pure water will freeze at 0°C at sea level and it will boil at 100°C. 
Scientists use the Kelvin system. It is based on absolute zero when all kinetic energy ceases. That means the molecules in an object would have no motion. This would happen at -273°C. 
Boy, that's cold!
  

 
 
Thermometers are used to measure temperature. For most purposes, an ordinary thermometercovering an appropriate range is satisfactory.

It is important to place the thermometer where the sun's rays have a minimum effect on it. Keep it out of direct sunlight if possible and consider the heat loss by radiation at night. The air temperature measured by the thermometer should represent general values for the area.

 

 
 
Materials:
1 2-liter bottle with water
"You can find many of these items around the house."
  1 plastic graduated tube
  1 rubber stopper with a hole that the plastic tube will fit in tightly (be sure that the stopper is large enough to fit tightly into the top of the 2-liter bottle.
  1 thermometer (regular room thermometer)
  Red food coloring (Actually, any color will do.)
  1 permanent black marker (Sharpie recommended)
  A small amount of Vaseline for lubrication

 
 
Directions:
 
 


 
 

Your thermometer should look like this.
1. Insert the plastic graduated tube into the hole in the rubber stopper. (You may want to use Vaseline to lubricate the tube so it will insert more easily.)
2. Put about 1.5 liters of water into the 2-liter bottle.
3. Add red food coloring to the water.
4. Insert the rubber stopper into the top of the bottle. You may need the Vaseline to help you insert the stopper into the top of the bottle. Be sure that it is a tight fit. The plastic tube should go down into the water by several centimeters.
5. Use a dropper to put water into the top of the tube. The tube should be about half full with water. Put more drops of food coloring into the water in the tube also.
6. Let the water become room temperature. If the temperature of the room and/or water in the thermometer increases too much, water may rise from the top of the tube. (Just a little messy. Be ready for this and don't have any important papers or "stuff" near by.)
7. Calibrate your thermometer:
Use an actual thermometer to measure the temperature of the room.
  Measure how high the water is on the plastic tube. 
  Record the temperature with a permanent marker on the plastic tube. 
  Repeat steps several times to get different temperatures recorded.
     Food for thought,
I mean, here are some good questions.
Why did the water expand?
Does water always expand when it is heated?
 
Does water always contract as it cools?
What would happen to life on our planet 
if that were true?
 
 Enrichment:  
Once you have calibrated your thermometer, check for accuracy; compare your thermometer's indications against an actual thermometer place near by. Are there any differences? How can you account these differences? 
Extrapolate?
What effect would using a glass bottle have on the accuracy of the thermometer? Why?
Extrapolate other desired temperatures on the tube. How will you determine the placement of the other numbers on the thermometer? How accurate are your extrapolations?

 
 
 
 
 Teacher Note:

You may have to add more food coloring from time to time if this is an ongoing project. The color in the 2-liter bottle will lose intensity. I think decomposition is due to light, but that's another experiment in itself!

 
 
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