How the thermometer works?

The video tutorial demonstrates how to create a simple thermometer using a plastic bottle, ethyl alcohol, water, and a straw. By observing the liquid level changes in the straw when the bottle is placed in hot and cold water, it illustrates the concept of liquid expansion and contraction with temperature changes. This experiment shows that liquids expand when heated and contract when cooled, which is the fundamental principle behind thermometers.

What new insight or understanding did you gain from this video?