Thermodynamics

Question 1

what is work a transfer of?

Answer 1

it is a transfer of mechanical energy into or out of a system, from or to the environment

Question 2

how does the total energy in a system change?

Answer 2

if energy is transferred into or out of the system

Question 3

Temperature (T)

Answer 3

the macroscopic measure of thermal energy per molecule

Question 4

Heat (Q)

Answer 4

the transfer of thermal energy between a system and its environment

Question 5

when is Q>0?

Answer 5

when heat transfers into the system

Question 6

when is Q<0?

Answer 6

when heat transfers out of the system

Question 7

what is an intensive property?

Answer 7

temperature (does not depend on the amount of material present)

Question 8

what is an extensive property?

Answer 8

thermal energy (depends on the amount of a material present)

Question 9

thermodynamics

Answer 9

concerns how macroscopic systems transfer and transform energy

Question 10

zeroth law of thermodynamics

Answer 10

if one object is in thermal equilibrium with a second object, and that second object is in thermal equilibrium with a third object, then the first and third objects are in thermal equilibrium with each other; if quantity of temperature are the same for two objects, then there is something fundamentally similar about the two

Question 11

thermal equilibrium

Answer 11

two bodies are in contact in such a way that heat is free to pass between them, but there is no change in heat because heat is passed equally in both ways

Question 12

state function

Answer 12

macroscopic properties that reflect the microscopic conditions of the system and predict the future behaviour of the system

Question 13

what are some state variables?

Answer 13

pressure, volume, moles, entropy

Question 14

what is Boltzmann’s constant?

Answer 14

k=1.38*10^-23J/K

Question 15

what are the three mechanisms by which heat transfer (movement of thermal energy) occurs?

Answer 15

conduction, convection, radiation

Question 16

conduction

Answer 16

direct contact in which highly agitated atoms cause the object in contact to vibrate more rapidly and heating up

Question 17

convection

Answer 17

usually occurs by a fluid becoming less dense than surrounding and rising due to buoyancy, where heat is transferred away from the flame by large-scale motion of a fluid

Question 18

radiation

Answer 18

absorption of the energy carried by light waves

Question 19

aside from change in heat transfer, what is another response of materials to temperature difference?

Answer 19

to change their physical dimensions, usually heating causes thermal expansion

Question 20

first law of thermodynamics

Answer 20

the total energy of the universe is constant

Question 21

what is the mathematical statement of the first law of thermodynamics?

Answer 21

change in E=Q-W

Question 22

what is the mechanical energy values of an ideal gas sealed in a container with a piston on top?

Answer 22

KE=PE=0, the only form of energy present is thermal energy

Question 23

for an ideal gas, what is the form of internal energy present?

Answer 23

kinetic energy of the atoms or molecules

Question 24

what is the internal energy of an ideal gas proportional to?

Answer 24

the object’s absolute temperature T

Question 25

if no heat is exchanged between a gas and the environment, what is the result of cooling or heating the gas?

Answer 25

cooling causes gas to compress, heating causes gas to expand

Question 26

what happens to the internal energy as gas compresses?

Answer 26

internal energy increases and so the gas heats up as it compresses

Question 27

what happens to the external energy as gas expands?

Answer 27

internal energy decreases and so the gas cools as it expands

Question 28

isobaric

Answer 28

a process that occurs at constant pressure, ex. piston is held constant

Question 29

isochoric

Answer 29

a process that maintains a constant volume

Question 30

what is the result of heating a gas with a locked piston, i.e. in an isochoric process?

Answer 30

there is no change in volume (W=0) but pressure would increase

Question 31

isothermal

Answer 31

a process whereby heat is allowed to pass freely between a system and its environment, so the temperature of the system remains constant

Question 32

what is the result of allowing a gas to expand at constant temperature (i.e. an isothermal process)

Answer 32

for gas to expand at constant temperature, the pressure must decrease

Question 33

adiabatic

Answer 33

a process that occurs when no heat is transferred between the system and the environment, and all energy is transferred as work (Q=0, change in E internal= -W)

Question 34

second law of thermodynamics

Answer 34

the entropy of an isolated system either stays the same or increases during any thermodynamic process

Question 35

what is the significance if entropy stays constant over a thermodynamic cycle?

Answer 35

the cycle is said to be reversible