Alcohol

Alcohol

It has temperature dependent property. It expands on increasing the temperature by heating and contracts on decreasing the temperature by cooling. Hence alcohol is used as a thermometric substance. It has the following main features:

1. Freezing and Boiling Point

Alcohol freezes at —115°C and boils at 78°C. Hence alcohol thermometers are not suitable for laboratory uses as the temperature encountered are usually alone the boiling point of alcohol. It can be used in polar regions where the temperatures are usually in the neighborhood of —40°C.

2. Color of Alcohol

It is a colorless liquid. It is usually colored red when used in a thermometer.

3. Wetting Property

Alcohol wets the internal glass surface. When it contracts, it leaves same alcohol sticking to the capillary tube. Due to this property reading, cannot be taken clearly.

4. Thermal Conductivity

It has a low thermal conductivity. Hence it takes a long time as compared to mercury to attain the temperature of the surroundings.

5. Thermal Expansion

Its expansion is nearly four times the expansion of mercury for the same rise of temperature. Hence, the scale divisions can be made larger in size, making it easier to read.