1. Chapter 16
Section 1

2. Kinetic Theory Kinetic Theory:
How particles in matter behave
3 Basic Assumptions of the Kinetic Theory
All matter is composed of small particles (atoms, molecules, and ions)
The particles are in constant, random motion
The particles are colliding with each other and the walls of their container

3. Thermal Energy
Look at Figure 2 – Does the ice cube appear to be moving?
Atoms in a solid are held tightly in place by the attraction between the particles.
The attraction between the particles is what gives solids a definite shape and volume

4. Thermal Energy Thermal Energy:
Total energy of a material’s particles
Includes kinetic = vibrations and movement within and between the particles
Also Potential = Forces that act within or between particles
What does the thermal energy do to the particles in the solid cube?
Causes them to vibrate
What happens if we lower the temperature of a substance?
Vibrate slower

5. Average Kinetic Energy
Molecules have kinetic energy at all temperatures – even absolute zero
Which molecules move slower – molecules at 0 degrees C or 100 degrees C?
Molecules at 0 degrees
Temperature therefore relates to the average kinetic energy of particles in the substance or how fast the particles move

6. Solid State Particles in a solid are closely packed together
Have a geometric arrangement of particles
Chemical and physical properties of a solid are attributed to the type of geometric arrangement
Example:
Ice Cube

7. Liquid State
What happens to a solid when thermal energy or heat is added to it?
As the thermal energy is added the particles on the surface of the ice cube vibrate faster
The particles on the surface transfer energy to other particles
Eventually the particles have enough kinetic energy to overcome the attractive forces

8. Liquid State Melting point:
Temperature at which a solid begins to liquefy
When the particles have enough kinetic energy to slip out of the ordered arrangement the ice melts
Energy IS required for the particles to slip out of the ordered arrangement
Heat of Fusion:
Amount of energy required to change a substance from the solid phase to the liquid phase at its melting point

9. Liquids Flow
Do particles have more kinetic energy as a solid or liquid?
Liquid
What does the extra kinetic energy allow the particles to do?
Partially overcome the attractions to other particles
Allows particles to slide past each other
Allows liquids to flow
Allows liquids to take the shape of their container
The attraction between particles is not quite overcome which is why liquids have a definite volume

10. Gas State
Do gas particles have enough kinetic energy to overcome the attraction between them?
Yes
Gases do not have a fixed volume
Fill the container they are in

11. Gas State How does a liquid become a gas?
The particles in a liquid are constantly moving
Some have more kinetic energy than others
Particles moving fast enough can escape the attractive forces
When particles escape the attractive forces they can enter the gas state
This process is called vaporization

12. Gas State 2 ways vaporization can occur? Evaporation Boiling
Vaporization that occurs at the surface of a liquid
Can occur at temperatures below the liquids boiling point
Have to have enough kinetic energy to escape the attractive forces of the liquid

13. Boiling Point Boiling occurs at a specific temperature Boiling Point:
Depends on the pressure on the surface of the liquid
Boiling Point:
Temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid
External pressure = force pushing down on a liquid to keep the particles from escaping
Heat of vaporization:
Energy required for the liquid at its boiling point to become a gas

14. Gases fill their Containers
Gas particles are moving quickly and are far apart
Do not have a definite shape or volume
Diffusion:
Particles spread throughout the “volume” until they are evenly distributed
Example:
Spraying air freshener in one half of the room

16. Heating Curve of a Liquid

17. Heating Curve of a Liquid
Heating curve graph shows the temperature change of water as thermal energy is added
What is going on when the temperature does not change?
All of the energy put into the ice is used to overcome the attractive forces
The temperature remains constant during melting
After the attractive forces have been overcome then the temperature can increase
The temperature remains constant again when water is boiling

18. Heating Curve of a Liquid

19. Plasma State Plasma: Is there an overall charge of the matter?
Matter consisting of positively and negatively charged particles
Is there an overall charge of the matter?
No, because there are equal numbers of the positively and negatively charged particles
How do we get plasma?
When particles undergo high energy conversions electrons from the atom can get stripped off
Plasma is found in lightning bolts and the Sun

20. Seams in a concrete driveway
Thermal Expansion
DISCUSS:
Seams in a concrete driveway

21. Expansion of Matter Thermal Expansion:
Increase in the size of a substance when the temperature is increased
What happens when the temperature increases?
When temperature increases particles move faster and separate
When the particles separate the entire object expands
What happens when the temperature decreases?
The particles move slower and the particles cannot over come the attraction
The particles move closer together and cause the object to shrink or contract

22. Expansion in Liquids Example: Thermometer
Addition of energy = particles moving faster
Particles move apart
Liquid in the thermometer expands / moves up the thermometer

23. Expansion in Gases Example: When the air is heated what happens?
Hot-air balloons
The air in the balloon is heated
When the air is heated what happens?
Distance between particles increases
The particles spread out causing the density of the hot air balloon to decrease
Because the density is lower than the cooler air outside the balloon can rise

24. Strange behavior of Water
There is always an exception to every rule
Water molecules have a highly positive and negative areas
Figure 11
The unlike charges are attracted to each other
Line up so that positive and negatives are near each other
This causes empty spaces to occur

25. Strange Behavior of Water
Are the empty spaces bigger in a solid or liquid?
Solid
So water expands when going from a liquid to a solid
This causes solid ice to be less dense than water
This is why ice floats on water

26. Amorphous Solids Amorphous is Greek for “without form”
Not all solids have a definite temperature at which they change from a solid to a liquid
Some soften and gradually change over a temperature range
These solids lack highly structured order
Example:
Glass and Plastics

27. Amorphous Solids
Instead of a geometric arrangement they have a long chainlike structure
Interactions between particles occur along the chain
Some amorphous solids form when a liquid changes to a solid too quickly
An orderly structure does not have time to form
Example: Obsidian – volcanic glass

28. Liquid Crystals
Liquid crystals DO NOT lose their ordered arrangement completely
Most substances lose their ordered arrangement as a liquid
Retain their geometric order in specific directions
Highly responsive to temperature changes
Use them to make LED watches, clocks, and calculators