Chapter 16 Notes

Objective – Describe how the kinetic theory applies to each state of

matter.

Explain thermal expansion.

Explain state changes on a heating curve.

There are four phases or states of matter: Solid, Liquid, Gas, and Plasma.

The kinetic theory explains the way particles behave in matter.

The kinetic theory is based on three assumptions:

All matter is made up of small particles.
The particles are in random, constant motion.
The particles collide with each other and the wall of the container.

State	Kinetic Theory	Particle Arrangement	Volume	Shape	Example
Solid	Vibrate	Held tightly in place	Definite	Definite	Ice, wood
Liquid	Slide over and past each other	Held loosely in place	Definite	Indefinite	Water, gasoline
Gas	Move freely	spread far apart	Indefinite	Indefinite	Oxygen, hydrogen
Plasma	Move freely	Charged particles Extreme temperatures	Indefinite	Indefinite	Sun, lightning, stars

Changes in State

Solid to a liquid - melting

Liquid to a gas - vaporization, evaporating

Gas to a liquid - condensation

Liquid to a solid - freezing

Gas to a solid - sublimation

The average kinetic energy is the temperature which lets you know how fast an object is moving. The faster the object moves, the higher the temperature.

When temperature decreases, the particles have less thermal energy.

When temperature increases, the particles have more thermal energy.

There are two types of solids.

Solids made of repeating geometric patterns called crystals have an orderly arrangement.

Solids with no orderly arrangement and no definite melting points are called amorphous.

Glass, plastics, and obsidian are examples of amorphous solids.

Liquid crystals are a special type of liquids that do not lose their ordered arrangement as they melt, and are in clocks, watches, and computers because of their response to temperature and electric fields.

In a heating curve, as shown in figure 7 on page 492, the first section (a) is in the solid state. As the substance is heated, the temperature rises until it reaches the melting point (b) and the temperature remains constant. As the substance is heated, the energy is used to convert from the solid to the liquid form, the heat of fusion, is reached. In (c) the substance is in the liquid state and the temperature rises until the boiling point is reached. At (d) the boiling point is reached and the temperature remains constant as the substance is heated. The energy required to change from a liquid to a gas, the heat of vaporization, is reached. After this point the substance will exist as a gas.

Melting point is the temperature that a solid begins to liquefy.

Heat of fusion is the energy required for an object to melt.

Vaporization is when particles move fast enough to escape the attractive forces of other particles.

Vaporization occurs as evaporation or boiling.

Evaporation occurs at the surface of a liquid at temperatures below the boiling point.

Boiling occurs throughout the liquid at a specific temperature depending on pressure on the surface of the liquid.

Boiling point is the temperature at which vapor pressure in the liquid is equal to the external pressure on the liquid surface.

The higher the atmospheric pressure; the higher the boiling point.

Thermal expansion is an increase in the size of a substance when the temperature is increased.

Objects expand when heated, and contract when cooled.

Thermal expansion in solids – power lines, expansion joints in bridges and concrete

Thermal expansion in liquids - thermometer

Thermal expansion in gases – hot air balloons

The triple point of water (it can exist as a solid, liquid, or a gas) is .61 kPa at .01 °C.

An exception to thermal expansion is water. Water expands as it freezes because the partially positive and partially negative charges line up a certain way. Ice floats on water because as a solid it is less dense.

Pressure is the amount of force per unit area.

Objective: Discuss temperature scales

Discuss Boyles’, Charles’, and Gay-Lussac (Pressure-Temperature) Law

Scale	Symbol	Freezing Point	Boiling Point	Room/ Body Temperature
Fahrenheit	° F	32	212	98.6
Celsius	° C	0	100	37
Kelvin	K	273	373	310

K = C + 273 C = 5/9 (F – 32) F = 9/5 C + 32

Know how to convert from one scale to the next. Know each of these three particular temperatures for each temperature scale.

Pressure - Force exerted per unit area

Volume - amount of space occupied by on object

Temperature - speed of the particles in an object (the faster they mover, the greater the temperature)