Matter consists of atoms and molecules and all substances consist of matter. Changing the state of a substance requires energy. Adding or removing thermal energy from a substance causes a change of state. Energy affects the attraction between the atoms or molecules and their rate of movement. A substance's temperature determines whether it occurs as a solid, liquid, or gas state.

A substance changes from a solid to a liquid at its melting point, from a liquid to a gas at its boiling point, and from a liquid to a solid at its freezing point. A different amount of energy is needed to change the state of different substances. For example, it takes much more energy to melt a solid metal into liquid than to melt an ice cube into water.

In this Virtual Lab you will examine how energy affects the state, the atomic or molecular activity, and the temperature of a substance.

Objectives:

• Explore how thermal energy affects different states of matter.
• Describe how the state of matter is affected by a change in temperature.
• Interpret and analyze temperature versus time graphs.
• Observe how the movement of atoms or molecules is affected by changes in thermal energy.

Procedure:

1. Click the video button. Then click Play on the video controller. Watch the video about melting and boiling points of substances.

2. Select the Water, Mercury or Iron button. The selected substance appears in its solid form inside the energy box. The energy box is able to add thermal energy to the substance or remove it from the substance at a constant rate. Inside the energy box, a sensor senses the temperature of the substance.

3. In your Journal, make a prediction about what you think will happen as heat is added to the substance.

4. Click the Heat button on the energy box. Observe what happens to the state of the substance, the atomic or molecular activity of the substance, and the temperature of the substance.

5. Click the Graph button to see a printout of a temperature versus time graph that shows what happened when heat was added to the substance. Record your observations in your Journal.

6. Click the Heat button on the energy box. Observe what happens to the state of the substance, the atomic or molecular activity of the substance, and the temperature of the substance.

7. Click the Graph button to see a printout of a temperature versus time graph that shows what happened when heat was added to the substance. Record your observations in your Journal.

8. Click the heat button on the energy box. Observe what happens to the state of the substance, the atomic or molecular activity of the substance, and the temperature of the substance.

9. Click the Graph button to see a printout of a temperature versus time graph that shows what happened when heat was added to the substance. Answer the fourth and fifth journal questions.

10. Click the Cool button on the energy box. Observe what happens to the state of the substance, the atomic or molecular activity of the substance, and the temperature of the substance.

11. Click the Graph button to see a printout of a temperature versus time graph that shows what happened when heat was removed from the substance. Answer the sixth and seventh journal questions.

12. Determine the approximate melting, boiling and freezing points of the substance by reading the graph. Record this data in the Table.

13. Repeat this activity with a different substance.