# Temperature

## temprature.jpg

Thermometers are common instruments for measuring temperature.  The early developers of thermometers were also skilled glass makers.

By Zwager (Own work) [Public domain], via Wikimedia Commons

Temperature is a measure of how much thermal energy is present in a body. Add thermal energy and the temperature goes up, take thermal energy away and the temperature goes down. Hot and cold are two terms that give us a since sense for the thermal energy in an object. Temperature scales allow us to be more specific in our descriptions of thermal energy. There are several temperature scales encountered in the study of fluids.

There are two scales commonly used to measure temperature:  Celsius and Fahrenheit.  The main differences between these scales is are in the difference in graduations used to define a change in temperature and each scale’s definition of zero.  Neither scale uses absolute zero as a reference, and two other scales (Rankine and Kelvin) are used when working with thermodynamic variables and equations of state.

Celsius Scale:  This scale uses a zero temperature that is referenced to the freezing point of water and has 100 graduations between the freezing point of water and the boiling point of water.

Fahrenheit Scale: This scale has a value of 32 at the freezing point of water and a value of 212 at the boiling point of water.  This results in 180 graduations between the freezing and boiling points of water.

Kelvin Scale:  This scale uses the same graduation as the Celsius scale but uses absolute zero as its reference temperature.

Rankine Scale:  This scale uses the same graduation as the Fahrenheit scale but uses absolute zero as its reference temperature.

## Learning Objectives:

Define temperature; explain the difference between the Fahrenheit, Celsius, Rankine, and Kelvin temperature scales.