Changes of State


Matter is always changing state. Look at the two pictures of Mount Rushmore in Figure below. The picture on the left was taken on a sunny summer morning. In this picture, the sky is perfectly clear. The picture on the right was taken just a few hours later. In this picture, there are clouds in the sky. The clouds consist of tiny droplets of liquid water. Where did the water come from? It was there all along in the form of invisible water vapor.

Both of these pictures of Mount Rushmore were taken on the same day just a few hours apart. Where did the clouds come from in the picture on the right?

Introduction to Changes of State

What causes clouds to form? And in general, how does matter change from one state to another? As you may have guessed, changes in energy are involved.

Lesson Objectives

  • Explain the role of energy in changes of state.
  • Outline the processes of freezing and melting.
  • Describe vaporization and condensation.
  • Define sublimation and deposition.