1. Chapter 16 Section 1
Kinetic Theory

2. Kinetic Theory An explanation of the behavior of molecules in matter
3 basic assumptions
All matter is composed of small particles (atoms, molecules, and ions)
These particles are in constant, random motion
These particles are colliding with each other and the walls of their container

3. Thermal Energy The total energy of a material’s particles
Kinetic energy + potential energy
AVERAGE KINETIC ENERGY=TEMPERATURE
Faster moving particles = higher temp.
Slower moving particles =lower temp.
Absolute zero = C (particle motion is so slow that no additional thermal energy can be removed)

4. Solid State Has a definite shape and volume
Particles are closely packed together and vibrating in place
Particles have a geometric arrangement

5. Liquid State Has a definite volume, but no definite shape
Particles slip out of their ordered arrangement and are able to move past each other
Still some attractive forces

6. Liquid State
Melting point – The temp. at which a solid begins to liquify
Heat of fusion – The amount of energy required to change a substance from the solid phase to the liquid phase at its melting point

7. Gas State No definite shape or volume
Particles have enough kinetic energy to overcome the attractive forces between them
Particles bounce and collide, filling their container

8. Gas State
Boiling point – the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid
Heat of vaporization – the amount of energy required for the liquid at its boiling point to become a gas

9. Gas State Evaporation Boiling Occurs at the surface of a liquid
Can occur at temperatures below the boiling point
Must have enough kinetic energy to escape the attractive forces of the liquid
Occurs throughout a liquid
Occurs at a specific temp.

10. Diffusion
Spreading of particles throughout a given volume until they are uniformly distributed
Occurs in solids and liquids, but most rapidly in gases
From high concentration to low concentration

11. Heating Curves Shows temp. change as thermal energy (heat) is added
Temp. remains constant during melting and while boiling
All energy is used to overcome attractive forces

12. Thermal Expansion
An increase in the size of a substance when the temp. is increased
Solids (gaps in sidewalks)
Liquids (thermometers)
Gases (hot air balloons)

13. The Strange Behavior of Water
Water molecules have highly positive and negative areas
As they cool, molecules align themselves by charge, so empty spaces occur in the structure
Water expands as it goes from liquid to solid
Ice is less dense than water (that’s why it floats!)

14. Plasma State
Matter consisting of positively and negatively charged particles (neural charge overall)
Very high energy  hard collisions of molecules electrons stripped off
Ex - stars, lightning bolts, neon tubes, etc.

15. Amorphous Solids Not all solids have a definite melting point
Some merely soften and turn into liquid over a range of temps.
They lack the ordered structures of crystals
Ex - glass and plastic (long, chainlike molecules)

16. Liquid Crystals
Start to flow during the melting phase similar to a liquid, but they do not lose their ordered arrangement completely
Highly responsive to temperature change and electric fields
Ex - LCD displays of watches, clocks, and calculators

17. Changes in Thermal Energy Experiment
Create a time/temperature table
Fill your beaker halfway with ice and cold water
Use your thermometer to measure the temperature of the water (DO NOT TOUCH THE THERMOMETER TO THE SIDES OR BOTTOM OF THE BEAKER) Record this temp. as time zero
Place your beaker on a hot plate over medium heat
Measure the temperature every minute and record it in your table
Create a graph using your data.
Write a paragraph describing what is happening in your graph.