Page 242 - Primary Five Science

3. Wall thermometer

This is the type of thermometer which is hung in our

houses and offices.

1. It measures temperature in that room

2. It uses mercury

Liquids used in thermometers

There are two liquids used in thermometers namely:

1. Mercury

2. Alcohol

Reasons why mercury is used in thermometers

 Mercury is highly visible

 Mercury is a good conductor of heat

 Mercury does not stick on the glass

 Mercury has even and regular expansion

 Mercury has a high boiling point.

Advantages of using alcohol over mercury

 It does not solidify easily

 Alcohol has a lower boiling point and therefore more

sensitive to temperature changes

Why water is not used in thermometer

 It is colourless so it not easily seen

 It sticks on the wall glass of the tube

 It does not expand uniformly
 It is a bad conductor of heat

 It needs a lot of heat to expand

 It evaporates

Conversion of scales