Properties of Matter

2. Properties of Matter • Chapter Four: Density and Buoyancy • Chapter Five: States of Matter

3. Chapter Five: States of Matter • 5.1 Liquids and Gases • 5.2 Solid Matter

4. Investigation 5A The Phases of Matter • How do the mass, volume, and densities of solid, liquid, and gas compare?

5. 5.1 Liquids and Gases • A fluidis a form of matter that flows when any force is applied. • Gases and liquids are both called fluids.

6. 5.1 Liquids and Gases • In a liquid, molecules can slide over and around each other. • This is why liquids flow and can change shape.

7. 5.1 Liquids and Gases • A gas is a phase of matter with high energy molecules that can expand to fill a container. • Molecules in a gasare free to move around and so gases flow just like liquids. Molecules in a gas have much more energy than molecules in a liquid.

8. 5.1 Liquids and Gases • Gases flow like liquids, but they also can expand or contract to completely fill any container.

9. 5.1 Pressure • Forces in fluids are more complicated than forces in solids because fluids can change shape.

10. 5.1 Pressure • A force applied to a fluid creates pressure. • Pressure acts in all directions, not just the direction of the applied force.

11. 5.1 Pressure • On the microscopic level, pressure comes from collisions between atoms. • Every surface can experience a force from the constant impact of trillions of atoms. • This force is what we measure as pressure.

12. 5.1 Pressure • The pressure inside your tire is what holds your car up.

13. 5.1 Pressure • There are two types of forces that act between atoms. • The strongest forces are between atoms that are bonded together into molecules and compounds. • A weaker type of force acts between molecules, or between atoms that are not bound together. • We call these weak forcesintermolecular forces.

15. 5.1 Intermolecular Forces • The phases of matter (solid, liquid, gas) exist because of competition between thermal energy and intermolecular forces. • When molecules have a large amount of thermal energy (high temperatures), intermolecular forces are overcome and the molecules spread apart, as in a gas.

16. 5.1 Intermolecular Forces • When molecules have a medium amount of thermal energy, they come together to form a liquid because the intermolecular forces are partially overcome.

17. 5.1 Intermolecular Forces • When molecules have a small amount of thermal energy, the intermolecular forces are stronger and molecules become fixed in place as a solid.

18. 5.1 Melting and boiling • The melting pointis the temperature at which a substance changes from a solid to a liquid.

19. 5.1 Melting and boiling • The temperature at which a liquid becomes a gas is called the boiling point.

21. 5.1 Melting and boiling points ofcommon substances • Materials have a wide range of melting and boiling points.

22. 5.1 Melting and boiling points ofcommon substances • Most materials have a higher density as a solid than as a liquid. • Water is an exception. • Ice wouldn’t float if ice were more dense than water! • Ice helps fish and other aquatic organisms to survive over long, cold winters because the protective layer keeps the water below it warmer.

23. 5.1 Evaporation and Condensation • Evaporationoccurs when molecules go from liquid to gas at temperatures below the boiling point. • Evaporation takes energy away from a liquid because the molecules that escape are the ones with the most energy. Sweat evaporating from skin removes energy and cools the body.

24. 5.1 Evaporation and Condensation • Condensation occurs when molecules go from gas to liquid at temperatures below the boiling point. Dew forms when water vapor in air condenses into droplets.

25. 5.1 Convection • Convectionis the transfer of heat through the motion of fluids such as air and water. • Convection occurs because fluids expand when they heat up. • Convection currents occur while heating water. • The hot water at the bottom of the pot rises to the top and replaces the cold water.

26. 5.1 The atmosphere of Earth • Air is the most important mixture of gases to living things on the Earth. • Air may seem like “nothing” but all the oxygen our bodies need and all the carbon needed by plants comes from air. • Molecular nitrogen (N2) and oxygen (O2) together account for 97.2 percent of the mass of air. • Argon and water vapor make up most of the rest.

28. 5.1 The atmosphere of Earth • As a tree grows, you will not see soil disappear to provide mass for the tree. • The oxygen and hydrogen atoms in the tree come from water. • The carbon atoms come from the carbon dioxide (CO2) in the air.

29. 5.1 The atmosphere of Earth • Earth’s weather is created by gigantic convection currents in the atmosphere.

30. 5.1 The atmosphere of Earth • Gravity creates pressure because fluids have mass and weight. • The Earth’s atmosphere has a pressure due to the weight of air. How does pressure change with altitude in the atmosphere?