Chem class 3

Question 1

What are the phases of matter?

Answer 1

Solid, liquid, gas

Question 2

When energy is added to a substance, that energy can be used to do one of two physical things. What are they?

Answer 2

Increase temperature (increase KE), Or cause a phase change (increase PE)

Question 3

What two things does vapor pressure depend on?

Answer 3

TEMPERATURE IN INTERMOLECULAR FORCES

Question 4

WHEN DOES LIQUID BOIL?

Answer 4

WHEN THE **VAPOR PRESSURE OF THE LIQUID =ATMOSPHERIC PRESSURE **

Question 5

The phase of a substance depends on what two properties besides intermolecular forces?

Answer 5

Temperature in pressure

Question 6

WHAT ASSUMPTIONS DO WE MAKE ABOUT IDEAL GASES?

Answer 6

I do gases are composed of molecules that take up no volume and experience NO intermolecular forces.

Question 7

What conditions are indicated by the letters STP?

Answer 7

1 atm 0C

Question 8

What is the volume of one mole of an ideal gas at STP?

Answer 8

22.4L

Question 9

Describe at the molecular level what happens to a solid when it dissolves.

Answer 9

Solute particles are separated and encapsulated by solvent molecules such that the solute is observed to dissolve.

Question 10

Define an electrolyte

Answer 10

And electrolyte is a solute that dissolves into charged particles in solution (has an i value greater than 1)

Question 11

Name at least three properties of liquids that depend on intermolecular forces.

Answer 11

Solubilty, vapor pressure, boiling point temperature, melting point temperature, viscosity, surface tension.

Question 12

What quantity is specified by the average kinetic energy of molecules of a substance?

Answer 12

Temperature.

Question 13

What phase do molecules have the most energy?

Answer 13

Gas phase

Question 14

At a given temperature which gas molecules travel faster: those with small molecular weights or large ones?

Answer 14

Gases with smaller molecular weights travel faster.

Question 15

What are the official names for the six phase changes?

Answer 15

Fusion (melting), Freezing, vaporization, condensation, simulation, and disposition.

Question 16

What happens at a molecular level when a substance changes phase?

Answer 16

Intermolecular forces are formed or broken.

Question 17

What is usually the densest phase of matter?

Answer 17

Solid, main exception to water, which is most dense in its liquid phase.

Question 18

What property is used to measure the amount of a given gas in a mixture of gases?

Answer 18

Partial pressure

Question 19

Give an example of a gas that most closely approaches ideal behavior

Answer 19

Helium

Question 20

What temperature and pressure conditions allow most gases to behave most ideally?

Answer 20

High temperatures and low pressures (or large volumes)

Question 21

Liquid –> gas

Answer 21

Vaporization (boiling)

Question 22

solid –> liquid

Answer 22

Fusion (melting)

Question 23

gas –> liquid

Answer 23

Condensation

Question 24

Liquid –> solid

Answer 24

Crystallization (freezing)

Question 25

gass–>solid

Answer 25

Deposition

• Heat is released
• Internal KE decreases
• Entropy decreases

-∆H, -∆S

Question 26

solid–>gas

Answer 26

**Sublimation

• Heat absorbed
• Internal KE increases
• Entropy increases

+∆H, +∆S**

Question 27

Boiling Point

Answer 27

**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**

Question 28

High Vapor Pressure means=

Answer 28

weak IMFs

Question 29

High freezing point=

Answer 29

strong IMFs

Question 30

Under what conditions are gases most soluble?

Answer 30

High pressure and low temperature

Question 31

How would you increase the solubility of sugar in water?

Answer 31

Increase T

Question 32

Solubility rules of Electrolytes

Answer 32

Always soluble : Group I ions, H+, NH4+, NO3-, CH3COO-, CIO4-**

USUALLY insoluble: Ag+, Pb^2+, Pb^4+, Hg2^2+, Hg^2+

Question 33

Ideal Gas Law

Answer 33

PV=nRT

R (gas constant)= 0.08 L atm/K mol

Question 34

Pressure units

Answer 34

1atm= 101kPa= 760 torr= 760mm Hg

Question 35

Volume units

Answer 35

1L= 1000mL= 1000cm^3= 0.001m^3

Question 36

Temperature units

Answer 36

C + 273= K

Question 37

What does it mean when a gas can exist in a liquid phase that has a temperature substantially greater than its Normal boiling point.

Answer 37

**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. )

Question 38

Water boils at a lower temperature at high altitudes. The most likely explanation for this is:

Answer 38

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. **

Question 39

What are the most important criteria for a gas to be considered ideal?

Answer 39

1. The molecules do not liquefy at low temperature.
2. The molecules do not experience intermolecular forces.
3. The molecules have negligible volume.

Question 40

What reqires more energy, Solid–>liquid, or Liquid–>gas?

Answer 40

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.

Question 41

How do you get specific heat?

Answer 41

Specific heat= heat capacity/mass