Mercury or quick-silver is a metal which is liquid. It has a very low melting point at minus 38.83 degrees celsius. It means that if the temperature falls below minus 38.83 degrees celsius, it will turn into solid. Under the conditions of room temperature, mercury is in the liquid state.
Invention of the thermometer
In about 1607, Galileo invented an instrument that could measure the rise of water in a glass tube with the rise in temperature. This instrument is called a thermoscope. Later, scientists modified it to add a scale to mark the rise of water. Subsequently, water was replaced with alcohol and mercury.