1. Section 1: Kinetic Theory
Chapter 16
Section 1: Kinetic Theory

2. Kinetic Theory
Kinetic Theory is an explanation of how particles in matter behave.
3 basic assumptions of kinetic theory:
All matter is composed of small particles.
These particles are in constant, random motion.
These particles are colliding with each other and the walls of their container.

3. Particles lose some energy during collisions with other particles, but the amount of energy lost is very small and can be neglected in most cases.

4. To help visualize Kinetic energy, think of each particle as a tiny tennis ball in constant motion.
These balls are bouncing and colliding with each other.
Mentally visualizing matter in this way can help you understand the movement of particles in matter.

5. Thermal Energy Think about an ice cube in hot soup.
Does the ice vibrate?
Remember kinetic theory: All matter is composed of particles that are in constant random motion.

6. Atoms in solids are held tightly in place by the attraction between the particles
This attraction between particles gives solids a definite shape and volume.
Thermal energy is the total energy of a material’s particles, including kinetic and potential.
When the temperature is lowered, particles have less thermal energy and vibrate slower.

7. What is thermal energy?

8. Average Kinetic Energy
Temperature is the term used to explain how hot or cold an object is.
In science, temperature means the average kinetic energy of particles in the substance, or how fast the particles are moving.
Ex: absolute zero and boiling water.
How are kinetic energy and temperature related?

9. Solid State The particles of a solid are closely packed together.
Most solid materials have a specific type of geometric arrangement in which they form when cooled.
The type of geometric arrangement that the solid forms is important.

10. Chemical and physical properties of solids can be attributed to the type of geometric arrangement that the solid forms.
What are chemical properties?
What are physical properties?

11. Liquid state
When thermal energy (heat) is added to a solid the faster moving particles jostle the slower moving particles causing them to move quicker as well by transferring energy to them.
When the solid’s particles gain enough kinetic energy they can slip out of their ordered arrangement , this is known as the solid’s melting point.

12. Melting point is the temperature at which a solid begins to liquefy.
Heat of fusion- The amount of energy required to change a substance from the solid phase to the liquid phase at its melting point

13. What is heat of fusion?

14. Liquids Flow
Particles in liquids have more energy than in of those in solids.
This extra energy allows the particles to break out of their rigid structures and slide over each other. This allows liquids to be fluid.
However they have not completely overcome the attractive forces, causing the particles to still cling together, giving liquid a definite volume.

15. Why do liquids flow?

16. Gas State
Gas particles have enough kinetic energy to overcome the attractions between them.
They do not have a fixed volume or shape so they can fill whatever container they are placed in.
How do you think liquids become gases?

17. This process is called vaporization. It can occur in two ways
They have enough energy to completely escape the attractive forces of the other particles.
This process is called vaporization.
It can occur in two ways
Evaporation-vaporization that occurs a the surface of a liquid and can occur at temperatures below the boiling point.
Boiling- occurs throughout the liquid when the right temperature and pressure is met.

18. Boiling point
Boiling occurs throughout a liquid at a specific temperature depending on the pressure on the surface of the liquid.
The boiling point of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure action on the surface of the liquid.
Heat of vaporization is the amount of energy required for the liquid at its boiling point to become a gas.

19. What is steam?
How does external pressure affect the boiling point of a liquid?

20. Gases fill their containers
Diffusion is the spreading of particles throughout a given volume until they are uniformly distributed.
It occurs in solids and liquids as well as gases, but it happens more quickly in gases.
Can you think of examples of diffusion?

21. Plasma State
Plasma is matter consisting of positively and negatively charged particles with an over all neutral charge.
The collisions of particles in plasma are so forceful that it can strip electrons from atoms.
Plasma is the most common state of matter in the universe. All stars are in the form of plasma. Lightning bolts, neon and fluorescent tubes, and auroras are all also plasma.

22. What is plasma?

23. Thermal expansion
Think about concrete. When it is poured there are intentional seams put in it. Why do you think these seams are there?

24. Expansion of matter
Thermal expansion is an increase in size of a substance when the temperature is increased.
This is caused by the particles separating from each other with the added energy.
When Temperature is lowered the attractive properties of the particles grows stronger thus shrinking the material. This is known as contraction.

25. Expansion of liquids and gases
An example of expansion of liquids would be a thermometer.
An example of expansion of gases would be a hot air balloon.

26. The strange behavior of water
Normally when temperature increases matter expands, however this is not the case with water.
Water is a polar molecule. When polar molecules are heated up their polarity draws them together making it denser.
When it is cooled off they push each other apart making it less dense. This is why ice floats on water.

27. Solid or Liquid?
Amorphous Solids are solids that have no definite melting point, but simply soften when at high temperatures.
Two examples would be glass and plastic
Some amorphous solids form when liquid changes to solid too quickly for an orderly structure to form.
An example would be obsidian.

28. What are two examples of amorphous solids?

29. Liquid crystals
These are another group of materials that do not change states in the usual manner.
Normally the ordered geometric arrangement of a solid is lost when the substance goes from solid to liquid.
Liquid crystals start to flow during the melting phase similar to a liquid, but they do not lose their ordered arrangement completely.

30. They are highly responsive to temperature changes and eclectic fields.
Scientists use these properties of liquid crystals to make liquid crystal displays or LCDs
These are used in watches, clocks, and calculators among other things.