Thermometer is a device used to measure the temperature of an object or place. The SI unit of temperature is Kelvin. Degree Celsius (°C) and degree Fahrenheit (°F) are other units of temperature. Thermometers are tubes of glass filled with mercury or alcohol. At the bottom of the tube is a wider part called the bulb. When the bulb is heated, the liquid in the bulb expands or gets larger, causing the liquid to rise in the tube. When the bulb is cooled, the liquid contracts or gets smaller, causing the liquid to fall in the tube. The bulb at the base of the thermometer should be immersed in the material to be measured. Thermometers could be analogue or digital, see Figure 30

In using thermometer, hold the thermometer at the top, do not hold the bulb of a thermometer and do not let the bulb touch the glass.

Safety!!
For safety, never leave a child alone while you are using a thermometer, specially glass thermometer

Key Terms

• Thermometer is the device used to measure the temperature of an object or place.