Weather La Niña - STEM Challenge
Homemade Bottle Thermometer
Thermometers are tools used to measure temperature. Meteorologists use thermometers multiple times a day. Liquid thermometers typically consist of a sealed narrow glass tube with a bulb at one end. This bulb is filled with alcohol or mercury to prevent it from freezing in colder temperatures. The tube is marked with graduations (lines) either in Celsius or Fahrenheit.
Have you ever wondered how a thermometer works? Find out by making your own bottle thermometer with materials found around your house or the classroom.
Materials:
empty bottle
water
warm water
bowl
rubbing alcohol
food colouring
transparent/semi transparent straw
modelling clay
marker
ruler
measuring cup
notepad
syringe or medicine dropper or very steady hands
The Experiment:
1. Combine equal parts water and rubbing alcohol in a measuring cup
2. Add a few drops of food colouring. Note that darker colours will be more visible.
3. Pour this mixture into the bottle to the point that it is ¼ full.
4. Use the permanent marker and ruler and mark lines on the straw at every centimeter.
5. Put the straw into the bottle and hold it so that it does not touch the bottom of the bottle but is suspended slightly above the bottom.
6. Wrap the modelling clay around the bottle and the straw, ensure a tight seal so no air can escape. This will seal the bottle and hold the straw in place keeping it suspended just above the bottom of the bottle.
7. With the syringe or medicine dropper (or very steady hands and the measuring cup) add a few more drops of the coloured liquid into the straw until the level of liquid in the straw is a few centimeters above the liquid in the bottle.
8. Make a note of how far up the straw the liquid sits. To do this - count the number of marks on your straw, beginning at the bottom and counting up. Record the number and the location that the temperature reading was taken, in your notebook.
For example: Kitchen, 3. This will be your control number and is best taken inside at room temperature.
9. Next, fill the bowl with warm water. Place the thermometer in the bowl and let it sit for a minute. Record this information
10. Next go outside and take a temperature reading there. Record your observation.
*If it’s very cold outside, you may need to keep an eye on the bottle to ensure the liquid level in the straw does not fall below the bottom of the straw. This will draw in air and change the calibration of the thermometer.
11. Take 2 to 3 more temperature readings in and around your classroom, house or school yard.. If it’s not cold outside, place the thermometer in the fridge or in a bowl of cold water.
Data Collection Chart
Review your data.
Where were your coldest and warmest locations?
What were your smallest and largest numbers measured?
Were the higher numbers recorded in warmer or cooler places?
What happened in colder places?
Did the liquid in the straw fall below the liquid in the bottle at any point? If so - what was the result?
How do you think that this experiment works?
Can you plot your data on a bar graph to display your results?
Were you actually recording temperature? Or the effects of temperature? How could it be possible to calibrate your homemade thermometer to record actual temperature?
Why do you think that we used alcohol in this thermometer as opposed to strictly water?
How It Works
When the liquid inside the bottle is warmed it expands. Since the top of the bottle is sealed the liquid can not expand in the bottle and therefore is forced up the straw. This is possible because the opening at the top of the straw is not sealed.
When the liquid inside the bottle is cooled it contracts. This will cause the liquid to descend back down the straw.
Water doesn’t respond to temperature change as quickly as alcohol does. That is why in this experiment we mixed half rubbing alcohol and half water. Real thermometers don’t use water, they commonly use mercury or alcohol.
