Temperature and Scales

What is Temperature?

A reliable measure of the hotness (or coldness) of a body is its temperature.

• A hotter body has a higher temperature.
• A colder body has a lower temperature.
• The device used to measure temperature is called a thermometer.

Temperature Scales

There are three common scales used to measure temperature.

1. Celsius Scale ($^{\circ}\text{C}$)

• Unit: degree Celsius.
• Most commonly used scale for clinical and laboratory work.
• Water freezes at $0^{\circ}\text{C}$ and boils at $100^{\circ}\text{C}$.

2. Fahrenheit Scale ($^{\circ}\text{F}$)

• Unit: degree Fahrenheit.
• Previously used in clinical thermometers.
• Normal human body temperature: $98.6^{\circ}\text{F}$.
• Relationship: $37.0^{\circ}\text{C} = 98.6^{\circ}\text{F}$.

3. Kelvin Scale ($\text{K}$)

• Unit: kelvin (Note: small ‘k’ for the unit name, capital ‘K’ for the symbol).
• Important: No degree sign ($^{\circ}$) is used with Kelvin.
• This is the SI unit of temperature used in scientific work.
• Absolute Zero: $0\text{ K}$ is approximately $-273.15^{\circ}\text{C}$, the lowest possible temperature.

Writing Conventions

• Capitalization: Names of scales start with a capital letter (Celsius, Kelvin). Units start with lowercase (degree Celsius, kelvin). Symbols are capital ($^{\circ}\text{C}$, $\text{K}$).
• Formatting: Leave a space between the number and the unit (e.g., $37 \text{ }^{\circ}\text{C}$, not $37^{\circ}\text{C}$).