This liquid is sometimes colored alcohol but can also be a metallic liquid called mercury. Both mercury and alcohol grow bigger when heated and smaller when cooled. Inside the glass tube of a thermometer, the liquid has no place to go but up when the temperature is hot and down when the temperature is cold. Mercury is very reactive and works best. But mercury is also very a radioactive element. So, if you break the thermometer, you could get in trouble (radio active posoning) Alcohol work well, it is not radioactive and can't kill you.
Okay, hope I helped
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Answer:
The chemical elements are arranged in order of increasing atomic number. The horizontal rows are called periods and the vertical columns are called groups. Elements in the same group have similar chemical properties. This is because they have the same number of outer electrons and the same valency.