L02: Matter

It’s a hot summer day and you are sitting outside at a picnic table with a tall glass of ice water in front of you. The ice is floating in the water and beads of condensation are forming on the outside of the glass. Without looking at a chemistry book, you know that the ice and water in the glass and the drops of liquid on the outside of the glass are all made of the same matter: water or H2O. Any substance that has mass and occupies space is considered "matter." Considering the glass of ice water, you might be aware of the common three phases of matter: solid, liquid, and gas. Solid water is ice; the liquid water sloshes around and takes the shape of its container. There is gaseous water, referred to as humidity, in the air around the glass. When molecules of the gaseous water in the air come in contact with the cold surface of the glass, they condense and change from the gaseous state to a liquid state which you see as droplets of water on the outside of the glass. As water changes its phase between a solid, a liquid, and a gas it remains water, a pure substance made up of two elements, hydrogen and oxygen in a constant ratio. Phase changes are considered physical changes.

Objectives for Lesson 2

After completing this lesson, you should be able to:

  • Identify the three states of matter 
  • Distinguish between physical and chemical properties 
  • Distinguish between physical and chemical changes 
  • Explain the differences between elements and compounds
  • Distinguish between mixtures and pure substances 
  • Develop methods of separating mixtures