Pearson Prentice Hall Physical Science: Concepts in Action

1. Pearson Prentice Hall Physical Science: Concepts in Action Chapter 3 States of Matter

2. 3.1 Solids, Liquids & Gases • Objectives: • 1. Explain how shape and volume can be used to classify materials • 2. Describe how kinetic theory and forces of attraction can be used to explain the behavior of solids, liquids and gases

3. How Shape & Volume Classifies Materials • Materials can be classified as solids, liquids, or gases based on whether their shapes and volume are definite or variable • Solid: is the state in which materials have a definite shape and definite volume • Definite means that shape and volume won’t change unless the material is acted on by an outside force

4. Liquid is the state of matter in which material has a definite volume but not a definite shape • Liquids will take the shape of their container • Gas: is the state of matter in which a material has no definite shape and no definite volume • Gases will expand to completely fill the volume & take the shape of their container This Photo by Unknown Author is licensed under CC BY-NC-SA

5. Almost all matter exists as a solid, liquid or gas on Earth • This is not true for the universe • In places with the temperature of stars, matter exists in a state called plasma • In 1995, scientists discovered a fifth state of matter called BCE (Bose-Einstein condensate) • At temperatures close to absolute zero (0 K or -273ºC), BCE groups of atoms behave as if they were a single particle

6. Kinetic Theory • Kinetic energy is the energy an object has due to its motion • Kinetic theory says: • 1. That all particles of matter are in constant motion • 2. There are forces of attraction among all particles of matter

7. Kinetic theory of gasses says: • 1. The constant motion of particles in a gas allows a gas to fill a container of any shape or size • 2. Particles in a gas are in constant, rapid, random motion • 3. The motion of 1 particle of gas is unaffected by other particles of gas unless they collide • 4. Forces of attraction among particles of gas can be ignored under ordinary conditions

8. Kinetic theory of liquids says: • 1. A liquid takes the shape of its container because particles in a liquid can flow to new locations • 2. The volume of a liquid is constant because forces of attraction keep particles close together • Kinetic theory of solids says: • 1. Solids have a definite shape and volume because particles in a solid vibrate about a fixed point

9. Adding/taking Energy out of a system • When you add energy to a system the particles begin to move faster • As they move faster they collide and create friction (Heat) • As they continue we get a phase change

10. Six Common Phase Changes • phase change: is the reversible physical change that occurs when a substance changes from one state of matter to another • Six common phase changes: • melting, freezing, vaporization, condensation, sublimation, and deposition

11. Temperature, Energy & Phase Changes • The temperature of a substance does not change during a phase change • For example, water temperature remains constant when boiling to go from liquid to gas or when condensing from a gas to liquid

12. Energy is either absorbed or transferred during a phase change • The amount of energy absorbed depends on the substance & is a unique physical property for each substance • Definition: heat of fusion is the amount of energy absorbed when going from a solid to a liquid

13. Exothermic changes occur when energy is released to the environment • An example of an exothermic change is water freezing since it releases its heat to the environment so that it can freeze • Endothermic changes occur when energy is absorbed from the environment • An example is water melting since it gathers as much heat as possible from the environment to melt

14. Melting & Freezing Water • The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes • Solid water (ice) has molecules in a fixed position that vibrate about a fixed point • Freezing produces molecules in an orderly arrangement • Liquid water has molecules that are attracted to each other and slide past each other due to special chemical bonds • Melting allows a less orderly molecular arrangement

15. Evaporation & Boiling • Vaporization is a phase change from a liquid to a gas • Vaporization is endothermic since liquid water absorbs energy in the form of heat from the surroundings to go from liquid to gas • Heat of vaporization is the amount of energy needed for a substance to change phases from liquid to gas • Heat of vaporization is a unique physical property for each substance

16. Evaporation is the process that changes a substance from a liquid to a gas below the substance’s boiling point • Evaporation is a process that takes place at the surface of a liquid and occurs at temperatures below the boiling point • Vapor pressure is the pressure caused by the collisions of vapor on the walls of the container • Vapor pressure increases as temperature increases

17. Q: How does surface area of a liquid affect the rate of evaporation? • Definition: the boiling point is where vapor pressure equals atmospheric pressure • Kinetic theory shows that as the temperature increases, water molecules move faster & faster until they have energy to overcome attractive forces of neighboring molecules • Definition: condensation is the phase change from a gas or vapor to a liquid

18. Definition: sublimation is the phase change from solid to a gas without going through the liquid phase • Example of sublimation is dry ice to CO2 at room temperature • Definition: deposition is the phase change from a gas or vapor to a solid without going through the liquid phase • Deposition is the reverse of sublimation • Example of deposition is frost on windows

19. Phase Changes Diagram This Photo by Unknown Author is licensed under CC BY-SA