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General Chemistry MCAT > Chapter 5: Heat Capacity, Phase Change, & Colligative Properties > Flashcards

Chapter 5: Heat Capacity, Phase Change, & Colligative Properties Flashcards

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1
Q

Phase changes arise through what?

Other words, phase change results when, ….

A

Changes in which INTERNAL ENERGY is distributed over MOLECULES and SPACE

Energy of a molecule INCREASES ⬆️ or DECREASES ⬇️, or when SPACES is ENLARGED ↔️ or REDUCED ➡️⬅️

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2
Q

Phase changes are accomplished via ______ or ______.

A

Heat; work

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3
Q

Heat Capacity (C)

A

Added energy required to INCREASE the TEMPERATURE of the substance by 1 DEGREE.
C = q/

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4
Q

In ISOTHERMAL EXPANSION OF GAS, we can….

A

EXPAND a gas at CONSTANT TEMPERATURE by ADDING HEAT during expansion

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5
Q

2 Heat Capacities for a substance

A
  1. ) Constant VOLUME heat capacity (Cv)

2. ) Constant PRESSURE heat capacity (Cp)

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6
Q

1) VOLUME of system held CONSTANT, then…

2) PRESSURE held CONSTANT and substance allowed to expand, some of the energy can …

A

1) The system can do NO PV work; ALL energy change must be in form of HEAT (means: NONE of energy going in system can escape as work done by system)
2) Leave the system as PV work done on the surrounding as VOLUME CHANGES

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7
Q

At CONSTANT PRESSURE, a substance can do what to energy with

A

Absorb; Expel

Cp > Cv

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8
Q

A compound can ABSORB energy at what type of PRESSURE & VOLUME?

How does this happen?

A

Constant

By the stretching of its bonds

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9
Q

More energy a molecule has, …

A

The more energy it can channel into STRETCHING bonds (opposed to raising temperature)

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10
Q

Bond stretching can account for …

So for a compound with LOTS of bonds, the VALUE of Cp does what?

A

LARGE amount of energy ABSORPTION

Approaches the value of Cv

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11
Q

The ratio of heat capacity (Cp/Cv) it’s called…

A

Isentropic expansion factors

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12
Q

As a # of molecular bonds INCREASES,

A

Gamma APPROACHES 1

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13
Q

Greater Heat Capacity (C),

A

Greater ABSORBANCE w/o temperature change

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14
Q

Intermolecular forces of a solid or liquid are much STRONGER than those of a _____

A

Gas

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15
Q

Temperature will always INCREASE when energy is ADDED to a substance at CONSTANT _______ or _______.

A

Volume; Pressure

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16
Q

Temperature is ALWAYS increased when?

A

When ENERGY is ADDED to a substance at CONSTANT volume or pressure

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17
Q

Water has a specific heat of what?

A

1 calg-1(degree)C-1

cwater= 1calg-1(degree)C-1

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18
Q

What’s a CALORIMETER?

A

Device that measures energy change

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19
Q

A COFFEE CUP CALORIMETER is an example of what?

A

It’s an example of CONSTANT PRESSURE b/c it measures ENERGY CHANGE at atmospheric pressure

20
Q

What is a BOMB CALORIMETER ?

A

It measures ENERGY CHANGE at CONSTANT VOLUME.

It tells the INTERNAL ENERGY CHANGE of a reaction

21
Q

Heat is ______ change.

Enthalpy Change associated with MELTING is called?

Enthalpy Change associated with BOILING is called?

A

Enthalpy

Heat Fusion

Heat of Vaporization

22
Q

Enthalpy change is a STATE CHANGE, therefore, the exact SAME Amount of HEAT absorbed during melting is released during ______.

A

Freezing

23
Q

Different types of PHASE CHANGES:

A

Solid to Liquid = Melting
Liquid to Solid = Freezing

Liquid to Gas = Vaporization
Gas to Liquid = Condensation

Solid to Gas = Sublimation
Gas to Solid = Deposition

24
Q

Entropy and Enthalpy signs for the phase changes:

A

Condensation: (+)
Vaporization: (+)
Sublimation: (+)

Freezing: (-)
Condensations: (-)
Deposition: (-)

25
Q

When entropy and enthalpy both have the SAME SIGN, what does temperature dictate?

A

The DIRECTION of the process

(Ex: HIGHER temps push the process toward INCREASE IN ENTROPY and a DECREASE IN ENTHALPY
LOWER temps push the SAME process towards a DECREASE in ENTROPY and aN INCREASE IN ENTHALPY )

26
Q

Phase changes at CONSTANT PRESSURE are governed by what?

A

Temperature

27
Q

_________ and _______ are two INTENSIVE PROPERTIES that help determine what?

A

Pressure; temperature

Phase of a Substance

28
Q

Phase diagram

A

Indicates phases of a substance at different PRESSURES AND TEMPERATURES

29
Q

Triple Point

A

One point where a substance can exist in equilibrium as a SOLID, LIQUID, AND GAS

30
Q

Heat fusion is…

A

The amount of heat that must be added to convert one mole of a substance COMPLETELY FROM A SOLID TO A LIQUID

31
Q

When water is at BOILING POINT (100 C), when heat is ADDED, the added energy does not raise the temperature b/c:

A

The added energy is used to BREAK bonds b/n water molecules

32
Q

At BOILING POINT, any added energy is used to break intermolecular bonds and NOT to INCREASE __________, so while the water is boiling, there is what?

A

Kinetic energy

- NO temperature increase

33
Q

Heating a solid at CONSTANT temperature will do what?

A

MELT the solid

34
Q

Colligative properties depend on what?

4 Colligative Properties of solutions:

A

Number of particles

  1. Vapor Pressure
  2. Boiling Point
  3. Freezing Point
  4. Osmotic Pressure
35
Q

Addition of a nonvolatile solute will ______ the VP of solution in direct proportion to the number of particles added.

A

Lower

36
Q

When does a substance boil?

When can the boiling point of a substance change?

A

When VP = local atmospheric pressure

By adding a solute

37
Q

Addition of a Nonvolatile solute does what to VP and BP?

A

It LOWERS the VP and ELEVATES the BP

38
Q

Van’t Hoff factor (i) has 2 values:

Expected value of ionic compound is …

A
  1. Expected 2. Observed

Number of ions created upon complete dissociation

39
Q

What is ION PAIRING?

How does ion pairing come about?

A

Momentary aggregation of 2 or more ions into a SINGLE particle

Due to the STRONG attractions b/n (+) and (-) ions

40
Q

Ion pairing INCREASES with _________ _________, and DECREASES with INCREASING ___________.

A

Solution concentration; temperature

41
Q

Endothermic (breaking bonds) heat = _______ bonds, which leads to ______ _____, which you can predict a ______ _______.

A

Weak; high VP; low BP

42
Q

Liquid solute, the impurities will ______ the MP

A

Lower

43
Q

Mole fraction of solute ⬆️, then solvent will be the _______ preventing the solute from ________.

A

Impurity, freezing

44
Q

Define OSMOTIC PRESSURE

A

A Measure of the tendency of WATER (or solvent) to move into a solution via OSMOSIS ( water that passes through a SEMIPERMEABLE membrane to a HIGH concentration)

45
Q

Define Osmotic Potential

A

Partial measure of a systems free energy

Pure WATER is assigned an osmotic potential of 0

46
Q

When a solute is ADDED, osmotic potential becomes ______.

At CONSTANT TEMPERATURE & PRESSURE, water flows from _____ osmotic potential to ______ osmotic potential.

A

Negative

Higher, Lower

General Chemistry MCAT (4 decks)

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