The atoms and molecules in a substance do not always travel at the same speed. This means that there is a range of energy (the energy of motion) among the molecules. In a gas, for example, the molecules are traveling in random directions at a variety of speeds - some are fast and some are slow.

 Temperature is a measure of the average heat or thermal energy of the particles in a substance. Since it is an average measurement, it does not depend on the number of particles in an object. In that sense it does not depend on the size of it. For example, the temperature of a small cup of boiling water is the same as the temperature of a large pot of boiling water. Even if the large pot is much bigger than the cup and has millions and millions more water molecules.

We experience temperature every day. When it is very hot outside or when we have a fever we feel hot and when it is snowing outside we feel cold. When we are boiling water, we wait for the water temperature to increase and when we make popsicles we wait for the liquid to become very cold and freeze.

Art by Doris Daou

 EXPERIMENT: Fill a large and small container with lukewarm water. Measure the temperature of the water in each container and record your results. Repeat the experiment with warm or cold water or with different sized containers.

Summary: Temperature is a measure of the average heat or thermal energy of the particles in a substance. Temperature does not depend on the size or type of object.