Gen chem 5 Heat capacity, phase change, colligative properties.txt
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- Def phase
- If all intensive macroscopic properties are constant, the system is homogenous and can be considered a phase
What does it mean when a phase change occurs, and what are the two mechanisms capable of creating a phase change
- When a phase changes, it means the internal energy has changed, or the space between molecules has changed.
- Work and heat can change a phase
Def heat capacity and give equation. what is a better name for it hint: more accurate description
A measure of the energy needed to change the temperature of a substance. Or the amount of energy a substance can absorb before changing temperature. Puts an energy quantity to each thermal unit.
- Internal energy capacity
How many types of heat capacities are there for any one substance. What are they
- Constant volume heat capacity
- Constant pressure heat capacity
Which is greater, Cv or Cp
Cv > Cp
What are the heat capacity equations and when do you use each? What are the symbols for each
- q=C(dT): heat capacity of an over all system
- q=mc(dT): specific heat capacity - heat capacity per unit mass
- Specific heat symbol: c
- Heat capacity symbol: C
What is the specific heat capacity if water
What is a calorimeter, what are the two types, and info do we get from each
- Calorimeter: device used to measure energy change
- Constant pressure: coffee cup calorimeter (because done at atmospheric pressure) tells heats of reaction
- Constant volume: bomb calorimeter tells internal energy change
Define heat of fusion and hear of vaporaization
- Heat of fusion: solid to liquid phase change (melting/freezing)
- Heat of vaporization: liquid to gas phase change (vaporization/condensation)
Define triple point, critical temperature, critical pressure, critical point
- Triple point: Single point where a substance can exist in equilibrium in all three phases simultaneously
- Critical temperature: temp above which a substance cannot be liquified, regardless of the pressure added
- Critical pressure: the pressure required to produce liquidification of a substance at critical temp
- Critical point: point defined by a substances critical temp and pressure. Beyond this point, a liquid has gas a liquid characteristics
What is a colligative property. What are these properties
- Colligative property: a property which depends on n umber of particles involved only. Type does not change anything
- 1. Vapor pressure
- 2. Boiling point
- 3. Freezing point
- 4. Osmotic pressure
Give equation for boilling point elevation. Why is this phenomena observed
- k(b)= specific constant of substance being boiled
- m= molality
- i= van't Hoff factor = number of particles a single solute will dissociate into when put in solution
- Nonvolatile solutes lower vapor pressure which in turn raises boiling point
What is freezing point depression and how is it similar/different from boiling point elevation (bpe). What is the equation
- Freezing point depression: change in melting point due to addition of solute
- Same as bpe because a nonvolatile solute must be added to an ideally dilute solution for an effect
- Different because it is not vapor pressure which is changed, but impurities in crystallization are created which lower freezing point
- Same as bpe, but use k(f) instead of k(b)
Define osmotic pressure. What is the equation.
- Measure of waters desire to move into a substance due to osmosis
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