1. States of matter and Phase Changes

2. Describing States of matter
You may have noticed that some materials have a definite shape and volume, and some materials do not Materials can be classified as solids, liquids and gases based on whether their shapes and volumes are definite or variable. Shape and volume are clues to how the particles within a material are arranged

3. The kinetic theory
Kinetic energy is the energy an object has due to motion The faster an object moves, the greater its kinetic energy is A ball thrown at 85mph has more kinetic energy than a ball traveling at 70mph

4. The kinetic theory of matter
The kinetic theory of matter says that all particles of matter are in constant motion Particles of matter are always moving, ALWAYS This theory explains the behavior of solids, liquids, and gases

5. Solids
Solids have recognizable shape and they all take up a certain amount of space The materials in these objects all exist in a solid state The molecules in a solid have a specific pattern

6. The behavior of solids
Solids have a definite volume and shape This is because the particles in a solid vibrate around fixed locations The molecules in a solid are positioned in fixed locations relative to their neighbors Each atom vibrates within its location, but it never switches places with other atoms

7. Liquids
Liquids have a definite volume, but not a definite shape A liquid always has the same shape as its container - water in a glass

8. The behavior of liquids
A liquid takes the shape of its container because particles in a liquid can flow to new locations The volume of a liquid is constant because forces of attraction keep the particles close together - H20 molecules attract to one another

9. Gases
Gas neither has a definite shape nor a definite volume A gas will take on the shape of its container The molecules in a gas are constantly moving and are not arranged in a particular pattern

10. The behavior of gases
The particles of a gas are NEVER at rest At room temperature, the average speed of the particles in a sample of gas move at about 1600km/hr Atoms move in a straight line until they bump into one another, then their direction is changed *Demo*

11. The kinetic Theory of gases
The constant motion of particles in a gas allows a gas to fill a container of any shape or size
Particles in a gas are in constant, random motion
The motion of one particle is unaffected by the motion of other particles unless the particles collide
Forces of attraction among particles in a gas can be ignored under ordinary circumstances

12. PHASE changes
A phase change is the reversible physical change that occurs when a substance changes from one state of matter to another
Melting
Freezing
Vaporization
Condensation
Sublimation
Deposition

13. Melting
When a solid experiences a phase change into liquid form Every substance has a unique “melting point” at which they turn to liquid

14. Freezing
The phase change in which a liquid changes into a solid Not all liquids freeze in cold temperatures, some liquids are able to freeze at room temperature

15. Vaporization
The phase change in which a liquid turns into a gas Occurs at a substance’s “boiling point”

16. condensation
The phase change in which a substance changes from a gas or vapor into a liquid
Dew on the grass in the morning
Water droplets forming on the outside of your cup on a hot day

17. sublimation
The phase change in which a substance changes from a solid to a gas without changing to a liquid first - Dry Ice

18. deposition
The phase change in which a gas or vapor changes directly to a solid without first changing into a liquid Ice on car windshield

19. Temperature and phase changes
One way to recognize a phase change is by measuring the temperature of the substance as it is heated or cooled The temperature of a substance does not change during a phase change

21. Energy and phase changes
Energy can either be absorbed or released during a phase change The energy most commonly used in phase changes is heat energy The absorption of energy during a phase change is called an endothermic change The release of energy during a phase change is called an exothermic change

22. Endothermic Changes
Endothermic changes happen when energy is absorbed by a system Water evaporating is an example of an endothermic change

23. Exothermic Changes
An exothermic reaction occurs when energy is released by a system into its surroundings A melting ice cube is an example of an endothermic change