# 14. Thermometers and temperature

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## Thermometers and Temperature

There are several ways to measure temperature using different types of thermometer. However, whichever type of thermometer is used, it needs to read the true temperature of the surroundings or material that it is measuring.

To do this, the thermometer must first be calibrated by adding a scale which is divided into 100 equal intervals (as the decimal system is easiest to work with).

These 100 equal intervals are spaced between two fixed points, which are definite temperatures at which some physical change always happens.

The lower fixed point is the temperature at which pure ice melts or pure water freezes (sometimes called the 'ice point'). Scientists decided to call this 0 degrees Celsius.

The upper fixed point is the temperature at which pure water boils (sometimes called the 'steam point'). Scientists decided to call this 100 degrees Celsius.

If we are using a liquid-in-glass thermometer, then this scale will be marked beside the thin tube which has liquid inside it. As the temperature rises, the liquid expands and rises up the tube and the top of the liquid column will enable us to read off the temperature from the scale.

GCSE Physics Keywords: Temperature, Intervals, Fixed point, Calibration

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