10-1

CHEMISTRY CHAPTERS 10-12

(Phases of Matter & Kinetic Theory)

Kinetic-Molecular Theory:

Three assumptions

1. Matter is composed of tinyparticles.

2. Particles of matter are in continual motion.

3. Total kinetic energy of colliding particles remains constant.

Basically:

  • Temperaturespeed of the molecules
  • Volume size of the container
  • Pressurehow hard/often

molecule hit the walls

Kenetic energy is dependent on temperature.

In elastic collisions of particles some loose energy while others gain energy, but there is no overall energy loss.

A fluid is a substance that can flow and therefore take the shape of its container.

10-2

Kenetic Theory with

Phases of Matter:

Solid-particles are static

Liquid-particles are sticky

Gas-particles are nearly free floating

10-3

Phase Changes

Temperature is a key to changing the phases of matter:

  • Raising temperaturecan melt a solid or boil a liquid
  • Lowering temperaturecan condense a gas or freeze a liquid

Pressure can also have an effect on phases:

  • Liquid nitrogen
  • Aerosol cans
  • Dry Ice
  • Many others

Pressure can effect evaporation as well:

10-4

Nature of Gases

  1. Expansion - a gas fills any container in which it is confined.
  2. Compressiblility - by use of pressure a gas can be expanded and compressed (no definite volume)
  3. Low density-which is due to particles being so far apart
  4. Diffusion - the process of spreading out spontaneously to occupy a space uniformly.
  5. Effusion- the process of gas particle passing through a tiny opening

Nature of liquids

  1. High Density - particles are much closer together than in the gas phase.
  2. Incompressible - there is little space between particles to take advantage of by compression.
  3. Diffusion- the process of spreading out spontaneously to occupy a space uniformly.
  4. Surface Tension - a force that tends to pull adjacent parts of a liquid's surface together, thereby decreasing surface area to the smallest possible size
  5. Evaporation- liquids may evaporate into a gas.



Diffusion:10-5


Effusion:

10-6

Nature of Solids:

  1. Crystalline Structures - solids arrange their particles in specific static patterns called crystals.
  2. Definite Shape and Volume - solids can hold a shape without a container and they generally do not flow.
  3. High Density & Incompressibility - due to the particles being static and close together.

  4. Low Rate of Diffusion-although millions of times slower than in liquids, solids will diffuse (spread or mix)

10-7

Boyle's Law:


The volume of a gas varies inversely with pressure, provided the temperature remains constant.

P1 V1= P2 V2

V1 = volume one P1 = pressure one

V2 = volume twoP2 = pressure two

10-8

Temperature Scales

Fahrenheit is a temperature scale base on common temperatures.

Celcius is a temperature scale based on the boiling and freezing points of water.

Kelvin is a temperature scale based on absolute zero.

Absolute Zero is 0 K.(-273 K) This temperature has not been reached but it is believed that a substance at this temperature would have no movement occurring at the atomic level.

Converting celsius to kelvin:K = C + 273

Charles' Law:

The volume of a gas varies directly with the (kelvin) temperature, provided the pressure remains constant.

V1 V2

T1 T2

V1 = volume oneT1 = temp one (kelvin)

V2 = volume twoT2 = temp two (kelvin)


10-9

Combining Gas Laws:

What if temp and pressure are both changing?

P1 V1 = P2 V2

T1 T2

V1 = volume one T1 = temp one (kelvin) P1 = pressure one

V2 = volume twoT2 = temp two (kelvin) P2 = pressure two

Daltons Law of Partial Pressure:

The total pressure of the mixture of gases is the sum of their partial pressures.

10-10

STP- is the abbreviation for standard temperature and pressure

Standard temperature - is 0oC or 100 K.

Standard pressure - is 760 mm or 1 atm

Avogadro's principle:

Equal volume of all gases, under the same conditions of temperature and pressure, contain the same number of molecules.

Molar volume is the volume occupied by one mole of a gas at STP.

The standard molar volume of a gas is the volume occupied by one mole of a gas at STP.

1 Molar volume is 22.4 liters

Therefore the density for any gas is:

D = _G M W__ (gram molecular weight)

22.4 L