Thermodynamics

Question 1

Volumetric Thermal expansion

Answer 1

Delta V = Beta•V•Delta T

Beta=coefficient of volumetric expansion; its value is equal to 3x linear expansion for same material (Beta=3alpha)

Question 2

Isolated system

Answer 2

Not capable of exchanging energy or matter with surroundings; total internal energy change is zero

Question 3

Closed System

Answer 3

Capable of exchanging energy but not matter with surroundings

I.e. Gases in vessels with movable Pistons

Note: most common system on MCAT

Question 4

Open system

Answer 4

Can exchange matter and energy with surroundings

I.e. Boiling pot of water, humans, uncontained combinations

Question 5

State functions

Answer 5

Independent of path taken to get to equilibrium (pressure, density, temp, volume, enthalpy (H), internal energy (U), Gibbs free energy, and entropy (S)

Question 6

Process functions

Answer 6

Describe path taken to get from one state to another (work and heat)

Question 7

First law of thermodynamics

Answer 7

The change in total internal energy of a system is equal to the amount of energy transferred in the form of heat (Q) to the system minus the amount of energy transferred from the system in the form of work

Delta U = Q-W

Delta U: positive value-increasing temp
Negative value- decreasing temp

Heat (Q): pos value-heat goes in; neg value: heat goes out

Work: pos. Value- works done BY the system (expansion); neg value-works done ON system (compression)

Question 8

Conduction

Answer 8

Direct transfer of Energy from molecule to molecule through molecular collisions; there must be a direct physical contact

Question 9

Convection

Answer 9

Transfer of heat by the physical motion of a fluid over a material; only liquids and gases can transfer heat this way

Question 10

Radiation

Answer 10

Transfer of energy by electromagnetic waves; radiation can transfer energy through a vacuum

Question 11

Change of heat energy

Answer 11

q=mc•Delta T

c is specific heat (for water 1 cal/(g•k)

The temp of a system will change in proportion to the amount of heat transfer unless the system is undergoing a phase change in which the temperature remains constant

Question 12

Change in heat energy during phase change

Answer 12

q=mL

q= amount of heat gained or lost
M=mass
L= heat of transformation or latent heat of the substance

Question 13

Heat of fusion

Answer 13

The phase change transformation of a liquid to a solid; occurs at melting point

Question 14

Heat of vaporization

Answer 14

The phase change from a liquid to a gas or from a gas to a liquid; occurs at boiling point

Question 15

Isothermal

Answer 15

Q=W

Constant temp so no change in internal energy

Question 16

Adiabatic

Answer 16

Q=0

No heat exchange; delta U=-W

Question 17

Isobaric

Answer 17

Constant pressure

Question 18

Isovolumetric

Answer 18

W=0

Delta U= Q

No change in volume, therefore no work done

Question 19

Entropy

Answer 19

The measure of how much energy is spread out, or how widely spread out your jeep it comes in a process

Delta S=Qrev/T

Qrev is the heat gained or lost in a reversible process

Units: J/(mol•K)

Question 20

Linear thermal expansion

Answer 20

Delta L = alpha•L•Delta T

Alpha= coefficient of linear expansion
T= temperature
L=length