# Unit 1- Thermodynamics

## Phases

• Solid- Crystalline structure, non-compressible

• Liquid- no structure, but touching, non-compressible

• Gas- No structure, spread out, compressible.

## Physical properties:

→Properties that can be used to identify the substance(element)

• Melting point- point when a solid becomes a liquid

• Boiling point(vaporization)-point when a liquid becomes a gas  (BP)

• Freezing point(solidification)-point when a liquid becomes a solid (FP)

• Density-how closely packed matter is in a given volume

• Atomic Radius(Pg 10+11 on reference table)-refers to the space a specific element occupies.

## Energy:

• Potential energy- stored energy

• Kinetic energy- (temperature? Kind of but not really)- energy of the motion of particles

## Temperature Units:

• Temp is the average measure of kinetic energy.

• Celcius

• Kelvin- absolute zero (no zeros)

• conversion- K= c + 273

## Phase Changes:

• Endothermic- Absorb heat

• Exothermic- release heat

## Calculating the change of heat:

• water:

• Heat of fusion 334 j/g (solid to liquid and back/ melting point)

• Heat of Vaporization 2260 j/g (liquid to gas and back/ boiling point)

• Specific Heat capacity 4.18 j/k(g) (Changes temp, but not phase)

• All on reference table (Physical constants of water)

• equation for Heat of fusion- q=mH`f`

• equation for Heat of Vaporization- q=mH`v`

• equation for specific heat capacity- q=mCAT

• m= mass

• H= heat (of fusion or vaporization depending on `f` and `v`)

• C= specific heat capacity

• AT = Delta temp (difference in temp)

## Gases:

• Particles are traveling in straight-line paths and are randomly distributed

• No definite shape or volume

• Large distances between particles, low densities

• Can be compressed

• Can be liquified at low temperatures and high pressures

## Standard Pressure Temperature: (STP)

• Pressure: 1 atm or 101.3 kPa or 760 torr

• Temperature: 0 C or 273 K

## Boyle’s Law:

• relationship between pressure and volume

• says that the volume occupied by a gas is inversely proportional to the pressure exerted on the gas

## Charles’s Law:

• Describes the relationship between volume and temperature

• Says that the volume occupied by a gas is directly proportional to the temperature(in kelvin)

• equation- V1/T1 = V2/T2

## The combined gas law:

• combines boyles and charles law

• Formula(On back of reference table) - (P1)(V1)/T1 = (P2)(V2)/T2

## Kinetic Molecular Theory: (KMT)

• gases move in a random, constant, straight line motion (Ideal gas)

• Have negligible volume (Ideals gas)

• no attraction between particles (Ideal gas)

• If gas molecules do collide no energy is lost or gained (Ideal gas)

• (none of this is actually true but we pretend it is to make the math work out, that’s why it says “Ideal Gas”)

## Ideal Gas Vs. Real Gas:

• Ideal Gas - Follows all rules above for gas.

• Real Gas - gas molecules do have a volume and weak attractive forces

• Real Gasses act more like Ideal gasses when there is a higher temperature, and lower pressure.

# Liquids:

## Vapor Pressure:

• The pressure that vapor exerts when the temperature of a liquid increases.

• Vapor pressure has a greater influence on boiling than temperature.

• A liquid will boil when its vapor pressure equals the pressure of the liquid above it

• Table for vapor pressure is on reference table.

## Calorimetry:

• heat stored in chemical bonds(like calories in your food)

• Food labels are actually kilocalories

• Specific heat-the heat required to increase the temperature of a substance by 1 degree

• The Specific heat of water is on the reference table

## Other: (Things to remember)

• The two elements that are liquid at room temperature are Bromium, and mercury

• The two elements that sublime at STP are Iodine, and Carbon Dioxide

• Sublimation- Solid to gas.

• When the volume increases, the pressure decreases.