Fall and Rise of Heated Mercury

It is observer that when a mercury in a glass thermometer is put in a flame , the column of mercury first descends and then rises.EXPLAIN?
- Aqib (age 18)
Karachi,PAK

Aqib, This observation can be easily explained if you carefully look into what is happening when the thermometer is put in a flame. First when the thermometer is put inside the flame, the glass containing the mercury expands and this causes the liquid to initially fall since the glass tube becomes wider. Soon the heat reaches the liquid and this causes the liquid to expand causing it to rise. This explains why the mercury first falls and then rises. Prathum

(published on 02/16/2013)