In this topic you will learn about heat and how it affects matter.

Heat affects different types of matter differently. With the same amount of heat, one type of matter may warm up more than another type of matter. You can measure how much each type of matter warms up by using a thermometer.

Thermometers are used to measure temperature. Temperature is a measure of how hot or cold something is. Temperature is measured in degrees. A degree is the unit of measurement for temperature. The symbol for degree is °. Heat is a form of energy that makes things warmer. Heat can be added to a material to raise the material's temperature. Some materials need more energy to cause the same change in their temperature than others. It takes more energy to heat water than it takes to heat soil to the same temperature.

A thermometer is a glass tube filled with a liquid. When a thermometer is in a warm place, the liquid in the thermometer rises. It rises because the liquid expands when it is heated. Matter that expands gets bigger. It takes up more space.

When heat is added to matter, the particles in the matter move faster. As the particles move faster, they move farther apart. This movement makes matter expand.

Heat moves quickly through some types of matter. For example, some metals are used to make cooking pots. Heat moves quickly from the stove to the metal. The pot gets warm. Heat does not pass quickly through other materials. These materials are called insulators. An insulator is a material that heat does not travel through easily. Some materials, like wool, cotton, and air, are good insulators.