1. 1
States of Matter
A brief overview

2. 1. Kinetic-Molecular Theory2
Describes a state of matter in terms of particles in motion.
Gas particles are far apart (mostly empty space)
Collisions between gas particles and their container are elastic
Gas particles are in constant, rapid, random motion
There are no forces of attraction between gas particles.
The temperature of a gas depends on the average Kinetic Energy of the particles
KE = ½ mv2

3. Gas Properties Expansion = expand to fill container
Fluidity = gas particles glide easily past each other
Low Density = because particles are so far apart, they are less dense than other states
Compressibility = gases can be compressed into a small volume
Diffusion = spontaneous mixing of gases due to random motion
Effusion = process by which gas particles pass through a tiny opening

4. Liquid Properties Definite volume and takes shape of its container
In constant motion, but particles are closer together (attractive forces are therefore more effective)
Fluid = particle mobility, usually flows downhill naturally due to gravity
Relatively high density = 100x more dense than in gas state
Relative incompressibility = due to packed particles
Ability to diffuse = mix with other liquids (slower than gases, increases with temp)

5. Liquid Properties Cont.
Surface Tension = a force that tends to pull adjacent parts of a liquid’s surface together (creates spherical droplets)
Capillary Action = attraction of the surface of a liquid to the surface of a solid
Evaporation = particles escape the surface of a non-boiling liquid to enter the gas state
Boiling = change of liquid to bubbles of vapor that appear throughout the liquid
Formation of Solids = when a liquid is cooled, energy of particles decrease

6. Solid Properties Hold relatively fixed positions
Particles are closely packed, highest intermolecular forces
Only vibrational movement, more ordered
2 Types of Solids
Crystalline Solids (consist of crystals)
Amorphous solids (particles arranged randomly
Definite Shape & Volume = some are geometrically regular

7. Solid Properties Cont.
Definite melting point = the kinetic energy of the particles overcome the attractive forces holding them together (amorphous solids don’t have definite melting point, and are often called supercooled liquids)
high density and incompressibility = substances are most dense when a solid
Low rate of Diffusion = extremely slow
Crystalline Solids arranged in crystal structures

8. 2. Intermolecular Forces3
2. Intermolecular Forces
Inter- vs. Intra-
Inter means between two separate particles
Intra refers to a force (or bond) within a particle
Example: CO2

9. Dipole-Dipole Forces:4
Dispersion Forces:
Weakest
Between nonpolar molecules
Example: oxygen
Dipole-Dipole Forces:
Stronger
Between polar molecules
Example: HCl
Hydrogen bonds:
Strongest
Between hydrogens and F, O or N
Example: water

10. 3. Phase Changes 5
GAS
LIQUID
SOLID

11. 4. Heating and Cooling Curves6
4. Heating and Cooling Curves
Heating Curve
Temperature (celsius) G
L + G L
S + L S
Time (min)