Chem class 3 Flashcards
What are the phases of matter?
Solid, liquid, gas
When energy is added to a substance, that energy can be used to do one of two physical things. What are they?
Increase temperature (increase KE), Or cause a phase change (increase PE)
What two things does vapor pressure depend on?
TEMPERATURE IN INTERMOLECULAR FORCES
WHEN DOES LIQUID BOIL?
WHEN THE **VAPOR PRESSURE OF THE LIQUID =ATMOSPHERIC PRESSURE **
The phase of a substance depends on what two properties besides intermolecular forces?
Temperature in pressure
WHAT ASSUMPTIONS DO WE MAKE ABOUT IDEAL GASES?
I do gases are composed of molecules that take up no volume and experience NO intermolecular forces.
What conditions are indicated by the letters STP?
1 atm 0C
What is the volume of one mole of an ideal gas at STP?
22.4L
Describe at the molecular level what happens to a solid when it dissolves.
Solute particles are separated and encapsulated by solvent molecules such that the solute is observed to dissolve.
Define an electrolyte
And electrolyte is a solute that dissolves into charged particles in solution (has an i value greater than 1)
Name at least three properties of liquids that depend on intermolecular forces.
Solubilty, vapor pressure, boiling point temperature, melting point temperature, viscosity, surface tension.
What quantity is specified by the average kinetic energy of molecules of a substance?
Temperature.
What phase do molecules have the most energy?
Gas phase
At a given temperature which gas molecules travel faster: those with small molecular weights or large ones?
Gases with smaller molecular weights travel faster.
What are the official names for the six phase changes?
Fusion (melting), Freezing, vaporization, condensation, simulation, and disposition.
What happens at a molecular level when a substance changes phase?
Intermolecular forces are formed or broken.
What is usually the densest phase of matter?
Solid, main exception to water, which is most dense in its liquid phase.
What property is used to measure the amount of a given gas in a mixture of gases?
Partial pressure
Give an example of a gas that most closely approaches ideal behavior
Helium
What temperature and pressure conditions allow most gases to behave most ideally?
High temperatures and low pressures (or large volumes)
Liquid –> gas
Vaporization (boiling)
solid –> liquid
Fusion (melting)
gas –> liquid
Condensation
Liquid –> solid
Crystallization (freezing)
gass–>solid
Deposition
- Heat is released
- Internal KE decreases
- Entropy decreases
-∆H, -∆S
solid–>gas
**Sublimation
- Heat absorbed
- Internal KE increases
- Entropy increases
+∆H, +∆S**
Boiling Point
**Boiling point is the temperature at which the condensation/ vaporization phase transitions occur.
Boiling point is more specifically when Pvap= Patm
External P is directly proportional to BP
IMP is directly proportional to BP**
High Vapor Pressure means=
weak IMFs
High freezing point=
strong IMFs
Under what conditions are gases most soluble?
High pressure and low temperature
How would you increase the solubility of sugar in water?
Increase T
Solubility rules of Electrolytes
Always soluble : Group I ions, H+, NH4+, NO3-, CH3COO-, CIO4-**
USUALLY insoluble: Ag+, Pb^2+, Pb^4+, Hg2^2+, Hg^2+
Ideal Gas Law
PV=nRT
R (gas constant)= 0.08 L atm/K mol
Pressure units
1atm= 101kPa= 760 torr= 760mm Hg
Volume units
1L= 1000mL= 1000cm^3= 0.001m^3
Temperature units
C + 273= K
What does it mean when a gas can exist in a liquid phase that has a temperature substantially greater than its Normal boiling point.
**The external pressure is greater than the vapor pressure.
A compound will exist as a liquid as long as the external pressure is greater than the compounds vapor pressure. **
(Once the vapor pressure equals the external pressure the substance boils. )
Water boils at a lower temperature at high altitudes. The most likely explanation for this is:
Water boils at a lower temperature at high altitudes. The most likely explanation for this is: **that at high altitudes the atmospheric pressure is lower than the altitudes. **
What are the most important criteria for a gas to be considered ideal?
- The molecules do not liquefy at low temperature.
- The molecules do not experience intermolecular forces.
- The molecules have negligible volume.
What reqires more energy, Solid–>liquid, or Liquid–>gas?
Liquid–>gas
because the heat of vaporization must be added to the total energy required to raise the temperature. Liquid to gas which greatly increases the amount of heat energy required.
How do you get specific heat?
Specific heat= heat capacity/mass
