Temperature and its Measurement
Temperature scales
Learn about the three temperature scales.
Your book names three temperature scales:
| Scale | Unit | Symbol | Used for |
|---|---|---|---|
| Celsius | degree Celsius | °C | most everyday use; clinical thermometers |
| Fahrenheit | degree Fahrenheit | °F | older use; not in most science now |
| Kelvin | kelvin | K | scientific work; the SI unit |
37.0 °C is the same as 98.6 °F. The SI unit of temperature is the kelvin.
Writing them correctly:
- Scale names start with a capital: Celsius scale, Fahrenheit scale, Kelvin scale.
- In degree Celsius and degree Fahrenheit, 'degree' starts with a small letter; so does the unit kelvin.
- The symbols °C, °F and K are capitals, and the degree sign (°) is never written with K.
- Leave a space between the number and the unit (37.0 °C), and no full stop after the symbol unless the sentence ends there.
Komal says she has a fever of 101 degrees. Which scale? Body temperature does not go above 42 °C, so it cannot be Celsius. Normal is 98.6 °F, so 101 degrees is on the Fahrenheit scale.
To change Celsius into kelvin, add 273.15: temperature in K = temperature in °C + 273.15. There is no limit to how hot something can be, but there is a lowest possible temperature, about −273.15 °C, which is 0 K. It is called absolute zero.
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