a glass thermometer is made of colored alcohol in a tube & alcohol is a kind of liquid ->  a glass thermometer is made of alcohol liquid in a tube  a glass thermometer is made of alcohol liquid in a tube & as the liquid in a tube expands , the height of the liquid in that tube will increase ->  if the alcohol liquid in the tube expands, then the height of the alcohol liquid will increase  if the alcohol liquid in the tube expands, then the height of the alcohol liquid will increase & if a material is heated , then the material will expand -> the height of the alcohol liquid changes because alcohol is heated