lecture 2

Question 1

what does an extensive variable depend on

Answer 1

depends on the amount of material
(in grams or moles)

Question 2

extensive variable example

Answer 2

heat
work
energy
mass
volume

hmv we : depends on size/amount of material

Question 3

what is an intensive variable

Answer 3

a variable that doesn’t depend on amount of material

Question 4

examples of an intensive variable

Answer 4

pressure
temperature
molar quantities

Question 5

how is a molar quantity an intensive variable

Answer 5

the quantity per mole doesn’t change

molar internal energy quantities don’t change with amount of reactants

Question 6

what is work

Answer 6

ordered/ organised motion

Question 7

what are the 2 forms of motion

Answer 7

mechanical (atom motion)
electrical current ( e- movement )

Question 8

force of magnitude is

Answer 8

|F|

Question 9

equation for work required to move an object a distance ( 🔺d) against an opposing force of magnitude.

Answer 9

🔺w = - |F| 🔺d

Question 10

what is expansion work

Answer 10

how temperature changes when gases expand

Question 11

what must we first consider with expansion work

Answer 11

we say that that the external pressure is constant

ignore the effects of gravity or friction

Question 12

what is force of magnitude

Answer 12

|F| = external pressure x the Area ur pushing against

Question 13

all 3 equations for change in work

Answer 13

🔺w = - |F| 🔺d

🔺w = - Pext x A x 🔺d

🔺w = - Pext x 🔺Volume

Question 14

what is work caused by

Answer 14

the gas expanding + pushing the piston of area ‘A’ against the external pressure by distance, D

organised motion

Question 15

what is ‘wrong’ with expansion work

Answer 15

the external pressure is not constant

Question 16

equation for work when external pressure slightly changes

Answer 16

dw = - Pext x dV

infinitesimally small change in volume

Question 17

what is change in volume and why can this be done

Answer 17

🔺V = Vf - Vi

bc volume is a state function

Question 18

what is a state function

Answer 18

when the current value is independent of the path to get there

Question 19

state function examples

Answer 19

volume, pressure, temperature, internal energy, enthalpy, entropy, free energy

Question 20

why are heat and work not state functions

Answer 20

their change is based on how u get from initial to final values

Question 21

how do u maximise work

Answer 21

reversibility + equilibrium

Question 22

what conditions must be met for the piston to be moved

Answer 22

the external pressure must be smaller than the internal pressure

in order for the most work to be done, external pressure must be as close to internal as possible while still being lower.

Question 23

what does performing the expansion with equilibrium conditions + it being reversible do

Answer 23

allows the external pressure to vary infinitesimally at each stage, while allowing it to always be smaller than the internal pressure.

Question 24

external pressure equation

Answer 24

Pext = Pint + dp

Question 25

the few integration equations are nkr added to look back at notes to see them 🤞🏼