What do tearing paper, chopping wood, and boiling water all have in common? They are all physical changes. Physical changes are transformations that alter the physical properties of a substance but do not result in new substances. For example, a block of wood may feel rough to the touch, but rubbing it with sandpaper will smooth its surface and make it feel soft.
Heat energy affects a material’s state of matter by changing its physical properties. This leads to fascinating physical changes like melting, boiling, vaporization, condensation, and sublimation.
During melting, a solid’s particles absorb heat energy and gain enough kinetic energy to overcome the forces that hold them together in a rigid structure. This change in physical property allows the particles to break apart and transform into a liquid. Ice melts into water.
When a liquid is heated, its molecules move faster and farther apart. This increase in kinetic energy, which is a direct result of temperature, is what causes a liquid to boil. The transformation of a liquid into a gas happens when its kinetic energy is high enough to overcome the intermolecular forces holding the molecules together.
Heat energy can also cause a substance to change its state from solid to liquid (freezing), or from gas to solid (condensation). It can also change the color of the substance. However, a color change is usually an indicator of a chemical reaction rather than a physical change. Learn more about the effect of temperature on the state of a substance with this article.