Name ___________________________________
Notes
The average kinetic energy of particles in matter is
directly proportional to temperature.
Kinetic Energy is the energy of motion.
Temperature is a measure of the average kinetic
energy of particles in a sample of matter.
Gasses are more compressible than liquids and solids.
This is because gas particles are much further apart than particles of liquids or solids.
There is a lot more space between particles of a gas than in other states of matter.
Temperature is directly proportional to the average kinetic energy of particles in a sample of matter.
When temperature increases, average kinetic energy increases.
When temperature decreases, average kinetic energy decreases.
Absolute zero is the temperature at which there is absolutely no motion of particles.
Absolute zero occurs at 0 Kelvin or -273 oC
http://resources.hwb.wales.gov.uk/VTC/solids_liq_gases/eng/Introduction/default.htm
SOLID
LIQUID
GAS
Temperature /
Kinetic Energy
LOW
HIGH
Space Between
Particles
LITTLE
A LOT
Intermolecular
Attractions
STRONG
WEAK
Evaporation can
also be called
Vaporization or
Boiling
(Boiling / Vaporization)
High Temperature
Low Temperature
Phase Changes
The 3 common states or phases of matter are: solid, liquid, and gas.
The 4 common phase changes are:
Melting – solid to liquid
Boiling - liquid to gas
Condensation – gas to liquid
Freezing – liquid to solid
Melting and Boiling are both going from lower to higher temperature.
Melting and Boiling are phase changes that occur by absorbing energy.
Freezing and Condensation are both going from higher to lower temperature.
Freezing and Condensation are phase changes that occur by releasing energy.
Particles of a Solid are very close together.
Particles of a Liquid can flow past one another.
Particles of a Gas are very far apart on average.
Particles of a Solid have the strongest intermolecular attractions for one another.
Particles of a Gas have the weakest intermolecular attractions for one another.
2
Heat is not temperature!
Heat is energy that is transferred due to a difference in temperature.
Heat flows from a warmer object to a cooler object until the two objects are the
same temperature.
Temperature is a measure of the average kinetic energy of particles in a sample
of matter.
During the process of any phase change (while the phase change is taking place)
heat is being converted to Potential Energy instead of Kinetic Energy.
That means kinetic energy stops changing. Since temperature is a measure of
average kinetic energy, that also means temperature stops changing.
During any phase change temperature will remain constant
because heat is being converted to Potential Energy at that time.
Below is the heating curve for water. Heat is being added at a constant rate.
GAS
Boiling/Condensation
o
Temperature ( C)
Boiling
LIQUID
Point of Water:
100 oC
Melting/Freezing
Point of Water:
Melting
0 oC
SOLID
Time (Heat being added)
During any of water’s phase changes potential energy is changing while average kinetic energy
stops changing. This means that during any of water’s phase changes, the temperature of the
water will remain constant.
3
INTERMOLECULAR FORCES - Attraction Forces Between Molecules
There are three main types of intermolecular forces:
- dispersion forces (the weakest)
- dipole forces
- hydrogen bonding (the strongest)
weakest
strongest
dispersion forces < dipole-dipole < hydrogen bonding
Hydrogen Bonding is the strongest of the intermolecular attraction forces.
Hydrogen bonds can only form between molecules of a compound with a
chemical formula that contains Hydrogen as well as Fluorine, Oxygen or Nitrogen.
It must have an H and at least one of the following: N, O, or F
Some substances that can form
hydrogen bonds between molecules:
HF
NH3
H2 O
Multiple strong Hydrogen Bonds form between molecules of Water (H2O).
This is why water has surface tension and a particularly high boiling point.
Hydrogen-bond
A Hydrogen from one water molecule attracts an Oxygen from another water molecule.
Compounds that have strong intermolecular attractions generally have
higher melting points and higher boiling points.
Compounds that have weak intermolecular attractions generally have
lower melting points and lower boiling points.
4
SOLID
Temperature /
Kinetic Energy
Space Between
Particles
Intermolecular
Attractions
LIQUID
GAS
LOW
HIGH
LITTLE
A LOT
STRONG
WEAK
Melting and Boiling both involve particles getting further apart.
A substance becoming a gas requires the breaking of intermolecular attractions!
Solids have the strongest intermolecular attractions between particles since particles of a
solid are very close together.
Gasses have the weakest intermolecular attractions between particles since particles of a gas
are very far apart.
Heat is energy that is transferred due to a difference in temperature. Heat is not temperature!
Heat will flow from a warmer object to a cooler object until the two objects are the same temperature.
During any of water’s phase changes, its potential energy is changing while its average kinetic
energy remains constant.
This means that during any of water’s phase changes, the temperature of the water will
remain constant.
5
Heat of Fusion: The heat needed to MELT one gram of a solid.
Heat of Vaporization: The heat needed to BOIL one gram of a liquid.
Heating Curve for Water
melting
boiling
The line that represents melting is shorter than the line that represents boiling.
This shows that water has a higher heat of vaporization than heat of fusion.
This means that it takes more heat to boil water than it does to melt the same amount of water.
Phase Diagram for Water
Atmosphere (atm) is
a unit of pressure
Pressure (atm)
Liquid
Boiling Point of
Water
1
The boiling point of water at
1 atm
o
is 373 K (100 C)
Solid
Gas
0.006
273
373
Temperature (Kelvin)
Kelvin (K) is
a unit of
temperature
Example Question:
A sample of water is held at a constant temperature of 300 K while the pressure is increased from
0.003 atm to 1 atm. The phase change that occurs is _________________________.
Triple Point: the point on a phase diagram representing the temperature and pressure at which the
three phases (solid, liquid, and gas) can coexist.
The triple point for water is 273 K and 0.006 atm. Find this point on the phase diagram above.
The triple point is where the three lines come together!
6
During any phase change, temperature will remain constant
because Heat is being converted to Potential Energy
o
Temperature ( C)
Draw and label a cooling curve for water, where heat is being removed at a constant rate.
Time (Heat being removed)
7