More Tips on How to Make Your Own Thermometer (Make Your Own Thermometer continued)
8. Watch the area where the liquid is on the straw. This can be your baseline for room temperature. Mark this on your bottle.
9. Begin bringing the bottle around to other areas of your home. Place it under a lamp, wrap your hands around it, put it beside a stove, etc. What happens to the liquid in the straw?
10. Mark each varying temperature. If you want, you can give values to the different markings by cross checking it with a commercially bought thermometer.
You should notice the liquid go up the straw when temperature rises, and go down the straw when it cools. The small pocket of air provided by the straw allows the liquid to expand upwards when the environment warms. In cases of extreme heat, the liquid will pour out over the straw.
Alcohol is a very volatile liquid, which means it evaporates quickly. You can teach your children this as an explanation for why we should always cap alcohol bottles, and in this case, cap the bottle while shaping the modeling clay and preparing the straw. This also means, however, that eventually the thermometer will stop working because the alcohol will be able to escape through the hole in the straw. If this happens, you can simply refill the mixture.
When your child no longer wants to use their home made thermometer, dispose of the bottle well and send it in for recycling. Because alcohol was used in the mixture, this bottle is no longer safe for storing drinking water or drinking liquids. If you want to use it for other purposes like water for gardening, it should be okay.
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