Ch 3 - Thermodynamics

Question 1

What is the zeroth law of thermodynamics?

Answer 1

states that objects are in thermal equilibrium when they are at the same temperature
- if a=b and b=c, then a=c

Question 2

What do objects in thermal equilibrium experience?

Answer 2

no net exchange of heat energy

Question 3

What is temperature?

Answer 3

• a qualitative measure of how hot or cold an object is

- quantitatively, it is related to the average kinetic energy of the particles that make up a substance

Question 4

What is thermal expansion?

Answer 4

describes how a substance changes in length or volume as a function of the change in temperature

Question 5

What is the difference between a system and the surrounding?

Answer 5

• a thermodynamic system is the portion of the universe that we are interested in observing
• the surroundings include everything that is not part of the system

Question 6

What are the 3 types of systems?

Answer 6

• isolated: do not exchange matter or energy with the surroundings
• closed: exchange energy but not matter with their surroundings
• open: exchange both energy and matter with their surroundings

Question 7

What are state functions?

Answer 7

• pathway independent and are not themselves defined by a process
• pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy

Question 8

What are process functions?

Answer 8

• describe the pathway from one equilibrium state to another

- work and heat

Question 9

What is the first law of thermodynamics?

Answer 9

• a statement of conservation of energy: the total energy in the universe can never decrease or increase
• an increase in U is caused by transferred heat into the system or performing work on the system
• U will decrease when heat is lost from the system or work is performed by the system

Question 10

What is the total internal energy of a closed system equal to?

Answer 10

the heat flow into the system minus the work done by the system
delta U = Q - W

Question 11

What is heat?

Answer 11

• the process of energy transfer between 2 objects at different temperatures that occurs until the 2 objects cone into thermal equilibrium (reach the same temperature)

Question 12

What is specific heat?

Answer 12

• the amount of energy necessary to raise one gram of a substance by one degree Celsius or one Kelvin
• specific heat of water is 1 cal/g.K

Question 13

What is the heat of transformation?

Answer 13

• during a phase change, heat energy causes changes in the particles’ potential energy and energy distribution (entropy), but no kinetic energy
• therefore, there is no change in temperature

Question 14

What are the 4 special types of thermodynamic systems in which a given variable is held constant?

Answer 14

• isothermal: the temperature is constant, and the change in internal energy is 0
• adiabatic: no heat exchanged
• isobaric: the pressure is constant
• isovolumetric (isochoric): the volume is constant and the work done by or on the system is 0

Question 15

What is the second law of thermodynamics?

Answer 15

states that in a closed system (up to and including the entire universe), energy will spontaneously and irreversibly go from being localized to being spread out (dispersed)

Question 16

What is entropy?

Answer 16

a measure of how much energy has spread out and how spread out energy has become

Question 17

How do microstates relate to entropy?

Answer 17

on a statistical level, as the number of microstates increases, the potential energy of a molecule is distributed over that larger number of microstates, increasing entropy

Question 18

Are natural processes irreversible or reversible?

Answer 18

• every natural process is ultimately irreversible
• under highly controlled conditions, certain equilibrium process such as phase changes can be treated as essentially reversible

Question 19

How do you convert between temperature units?

Answer 19

F = 9/5.C + 32
K = C + 273

Question 20

What is the coefficient of linear expansion?

Answer 20

deltaL = alpha.L.deltaT

constant (alpha) that characterizes how a specific material’s length changes as the temperature changes

Question 21

What is the coefficient of volumetric expansion?

Answer 21

deltaV = beta.V.deltaT

a constant that characterizes how specific material’s volume changes as the temperature changes

Question 22

What is the maximum distance that 2 object can be from one another and still adhere to the zeroth law of thermodynamics?

Answer 22

• there is no set distance

- as long as the 2 objects are in thermal contact and at the same temperature, they are in thermal equilibrium

Question 23

What does a negative or positive change in internal energy mean?

Answer 23

• neg: decreasing temperature

- pos: increasing temperature

Question 24

What does a negative or positive heat mean?

Answer 24

• neg: heat flows out of the system

- pos: heat flows into the system

Question 25

What does a negative or positive work mean?

Answer 25

- neg: work is done on the system (compression) | - pos: work is done by the system (expansion)

Question 26

How much heat is required to raise 1 g of water by 1 C?

Answer 26

- 1 calorie (cal) - 1 Calorie needed to raise 1 kg of water by 1C 1 Cal = 1000 cal = 4184 J

Question 27

What is conduction?

Answer 27

the direct transfer of energy from one molecule to another through molecular collisions

Question 28

What is convection?

Answer 28

the transfer of heat by the physical motion of a fluid over a material

Question 29

What is radiation?

Answer 29

the transfer of energy by electromagnetic waves

Question 30

What equation relates heat gained or lost by an object and the changes in temperature of that object?

Answer 30

q = mcdeltaT

Question 31

How do you calculate heat energy of a phase change?

Answer 31

q= mL | L is the heat of transformation (latent heat)

Question 32

What are the terms for the following: - solid to liquid - liquid to solid - liquid to gas - gas to liquid - solid to gas - gas to solid

Answer 32

- s>l = fusion or melting - l>s = freezing or solidification - l>g = boiling, evaporation, or vaporization - g>l = condensation - s>g = sublimation - g>s = deposition

Question 33

How is entropy calculated?

Answer 33

deltaS = Qrev/T --> J/mol.K

Question 34

What is the relationship between entropy of a system and its surroundings for any given thermodynamic process?

Answer 34

- Suniverse = Ssystem + Ssurroundings > 0 - entropy of the isolated system and surroundings will never decrease; either remain 0 or increase - entropy of a system can decrease as long as the entropy of its surroundings increased by at least as much