What is Temperature?
Temperature can be a difficult property to define. In our daily life, we use the word temperature to describe how hot or cold an object is. In physics, temperature is the average kinetic energy of particles moving in a substance.
How is Temperature Measured?
The temperature is measured with a thermometer. There are many different scales and standards for measuring temperature, including degrees Celsius, degrees Fahrenheit, and degrees Kelvin. They are discussed in more detail below.
How does a Thermometer work?
Thermometers take advantage of a scientific property called thermal expansion. Most substances expand and take up more volume as they get hotter. Liquid thermometers have some sort of substance (formerly mercury, but today it’s usually alcohol) contained in a small glass tube.
As the temperature increases, the liquid expands and continues to fill the tube. As the temperature drops, the liquid shrinks and takes up less space in the tube. The temperature can then be read using the calibration lines on the side of the tube.
There are three main temperature scales in use today: Celsius, Fahrenheit, and Kelvin.
Celsius – The most common temperature scale in the world is degrees Celsius. Celsius uses the unit “degrees” and is abbreviated as °C. The scale sets the freezing point of water at 0°C and the boiling point of water at 100°C.
Fahrenheit – The most popular temperature scale in the United States is the Fahrenheit scale. Fahrenheit sets the freezing point of water at 32°F and the boiling point at 212°F.
Kelvin – The standard unit of temperature most used by scientists is Kelvin. Kelvin does not use the ° symbol like the other two scales. When you write temperature in Kelvin, you simply use the letter K. Kelvin uses absolute zero as the zero point on its scale. It has increments similar to degrees Celsius in that there are 100 increments between the freezing point and the boiling point of water.
Converting Between Scales
Celsius and Fahrenheit
°C = (°F – 32)/1.8
°F = 1.8 * °C + 32°
Celsius and Kelvin
K = °C + 273.15
°C = K – 273.15°
Absolute zero is the coldest possible temperature that any substance can reach. It is equal to 0 Kelvin or -273.15°C (-459.67°F).
Temperature and the State of Matter
Temperature affects the state of matter. All substances of matter will go through different phases as the temperature increases, including solids, liquids, and gases. An example of this is water that changes from ice (solid) to water (liquid) to vapor (gas) as the temperature increases.
Interesting Facts about Temperature
Temperature does not depend on the size or number of an object. This is called an intensive property.
The Fahrenheit scale is named after Dutch physicist Daniel Fahrenheit.
Temperature is an amount different from the total heat energy in a substance, which depends on the size of the object.
Degrees Celsius are named after the Swedish astronomer Anders Celsius. Degrees Celsius were originally called “C”.
As substances approach absolute zero, they can acquire interesting properties such as superfluidity and superconductivity.