SAN ANTONIO - Kids going stir crazy at home? While school is just around the corner, below is how to make a cool homemade thermometer that they'll be talking about on the first day of classes.
Jar with an air tight lid
Straw (clear works best)
Isopropyl rubbing alcohol
Hot glue gun (putty can be substituted for younger kids)
Food coloring - Any tool or device to puncture a hole in the lid of the jar
Refrigerator, hot water in a shallow container, ice cubes mixed with water in a separate shallow container
Puncture a hole in the lid of the jar. Make sure it’s large enough to fit the straw. Kids, have an adult help you with this step!
Insert the straw through the hole in the lid. Elevate the straw slightly off the base of the jar. This will allow for the movement of liquid up the straw as the temperature rises. The straw can be tilted or straight.
Using the glue gun (**set on low or you’ll melt the straw**), seal the space between the straw and the hole on the top of the lid.
Important: This needs to be airtight, or the thermometer won’t work. As an added layer of sealant, you can also apply the glue to the underside of the lid. Allow the glue to dry, which should only take a few minutes. Feel free to apply more glue/sealant for reassurance. Side Note: for younger kids, putty can be substituted for the warm glue. However, in my experience the putty doesn’t hold an airtight seal for very long, whereas the glue is pretty much permanent once dry – as long as you don’t pull the straw free. Similar procedures online use play dough, but I had little success with it. This is also a good time to experiment with different materials as a sealant!
Pour rubbing alcohol into the jar, filling about the bottom ¼ of the jar. Now add a little bit of water. Overall, there’s usually no need to have the jar more than 1/3 full of the liquid mixture. Side Note: For best results, cool the alcohol before pouring it into the jar. You can use a refrigerator or a container of ice cubes mixed with water to cool the alcohol (it won’t freeze, so toss it in the freezer if you’d like). This way, you’ll see results pretty quickly as the alcohol/water mixture adjusts to room temperature. Also, you’ll get different results with different ratios of alcohol to water. The more alcohol you have in the jar, the more sensitive the thermometer will be to a temperature change, and the more likely you’ll be to experience an overflow through the top of the straw.
Add a few drops of food coloring to the liquid in the jar and stir.
Screw the lid/straw apparatus back onto the top of the jar. If you started with chilled alcohol and have an airtight seal, you should see the liquid start rising up the straw almost immediately.
Hold the completed thermometer in your hands, and after 30 to 60 seconds, you should notice the liquid higher in the straw due to your body heat warming it.
Also, place the thermometer outside in the sun or in a shallow container of hot water. The liquid should rise up the straw. Next, place it in a shallow container of water mixed with ice. You should see the liquid drop.
Questions? Please feel free to send Adam an email -- firstname.lastname@example.org
While experimenting with your thermometer, you might experience an overflow of the liquid. To prevent this from happening, you can use the glue gun to connect straws together in order to make the thermometer longer. Just be sure it's an airtight seal between the straws, or liquid will leak out.
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