THE PHASES OF MATTER. Solid: holds its shape and does not flow. The molecules in a solid vibrate in place, but on average, don t move very far.

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1 THE QUESTIONS What are the phases of matter? What makes these phases different from each other? What is the difference between melting, freezing, boiling and condensation? How do you interpret a Temperature vs. time graph?

2 THE PHASES OF MATTER Solid: holds its shape and does not flow. The molecules in a solid vibrate in place, but on average, don t move very far.

3 THE PHASES OF MATTER Liquid holds its volume, but does not hold its shape it flows. Liquids flow because the molecules can move around each other.

4 THE PHASES OF MATTER Gas: flows like a liquid, but can also expand or contract to fill a container. A gas does not hold its volume. The molecules in a gas have enough energy to completely break away from each other.

5 THE PHASES OF MATTER Intermolecular forces: Forces that attract molecules to each other when they are close together. These are not chemical bonds (covalent, ionic or metallic).

6 INTERMOLECULAR FORCES In all matter, there is a constant competition between temperature and intermolecular forces. When temperature (or kinetic energy) wins the competition, molecules fly apart and you have a gas. When intermolecular forces win the competition, molecules clump tightly together and you have a solid. Liquids are somewhere in between.

7 THE PHASES OF MATTER Chemical bonds are much stronger than intermolecular forces.

8 REVIEW

9 THINK OF WATER!! What is the difference between melting, freezing, boiling and condensation? Ice (solid) melts into water (liquid). Water (liquid) freezes into ice (solid). Water (liquid) boils into steam (gas). Steam (gas) condenses into water (liquid).

10 Notice temperature is constant while ice melts!

11 THE QUESTIONS What are the phases of matter? What makes these phases different from each other? What is the difference between melting, freezing, boiling and condensation? How do you interpret a Temperature vs. time graph?

12 MELTING/FREEZING Melting point: Temperature at which a substance changes from a solid to a liquid. Freezing point: Temperature at which a substance changes from a liquid to a solid. What is the difference between these two points? There is no difference!! It is the same temperature!!

13 BOILING/CONDENSATION Boiling point: Temperature at which a liquid becomes a gas. Condensation point: Temperature at which a gas becomes a liquid. What is the difference between these two points? There is no difference!! It is the same temperature!!

14 Notice temperature is constant while ice melts!

15 EVAPORATON Temperature measures the average kinetic energy of particles in a sample. Some particles are moving very fast and some are moving slowly. The particles that are moving very fast can escape the sample and enter the gas phase. This is called evaporation. This is why water evaporates at room temperature. Evaporation does not happen at 100 o C!!

16 10.3 SUBLIMATION Sublimation: Process by which a solid can change directly to a gas when heat energy is added.

17 PHASES OF MATTER On Earth, pure substances are usually found as solids, liquids, or gases. These are called phases of matter.

18 MELTING AND BOILING POINTS OF COMMON SUBSTANCES Materials have a wide range of melting and boiling points.

19 THE 4 TH PHASE - PLASMA Plasma: Occurs at temperatures greater than 10,000C. Plasma is not a common phase of matter and requires tremendous amounts of energy to sustain. Matter becomes ionized (electrons are stripped from their atoms). Electric current can also strip electrons from their atoms. Lightning ionizes the molecules in air.

20 THE ANSWERS What are the phases of matter? Solid, liquid and gas. What makes these phases different from each other? What is the difference between melting, freezing, boiling and condensation? How do you interpret a Temperature vs. time graph?

21 THE ANSWERS What is the difference between melting, freezing, boiling and condensation? Think of water!! Ice (solid) melts into water (liquid). Water (liquid) freezes into ice (solid). Water (liquid) boils into steam (gas). Steam (gas) condenses into water (liquid). How do you interpret a Temperature vs. time graph? Study!!!