What is the easiest way to make a thermometer?

1 find a smaller bottle, not too small, like the one that used to contain penicillin. It is better to have a rubber plug. Just fill the bottle with colored water, such as pen water. You don't need to cover it.

Find a straw, drink a refreshing test tube, and put the straw through the cork to make it airtight, so that it won't leak.

Finally, use this cork with a straw to plug the small bottle tightly, so that it won't leak. When the cork is sealed, the red water in the bottle naturally comes up. If the water level is not obvious, you can also blow some air from above the straw, and a lot of water will enter the pipe.

When in use, the water in the straw will rise in hot water and fall in cold water.

Other methods:

Use a larger glass bottle with a rubber stopper, insert the stopper into a thinner and longer drinking straw, fill the bottle with colored water (water+appropriate amount of red ink), and cover the rubber stopper with the straw-make the liquid column in the tube shorter.

A very simple thermometer prototype has been made.

Put the "thermometer" into a larger container, soak the vial in cooler water in the container, put it into the water with a standard thermometer, and mark the liquid level in the straw when the thermometer indicates t 1.

Replace the water in the container with hot water, repeat the above process, and mark t2.

Divide (t2-t 1)/n equally at two marks on the test tube, and mark the temperature value of each battery!