Physics 1A: Thermodynamics

Front 1

Temperature

Back 1

the quantity that tells how hot or cold something is compared to a standard

Front 2

T(F)

Back 2

9/5T(C)+32

Front 3

Heat

Back 3

Heat is energy that transfers from one substance to another because of a temperature difference

Front 4

What's related to Temperature?

Back 4

the average kinetic energy of molecules in a substance

Front 5

What is heat related to?

Back 5

both KE of the molecules and the number of molecules there are

Front 6

Internal energy

Back 6

the grand total of all energies inside a substance. A substance does not contain heat--it contains internal energy

Front 7

Heat

Back 7

energy in transit. It moves from a higher temperature object to a lower temperature object.

Front 8

Thermal contact

Back 8

the term for the heat flowing from one object to another

Front 9

Thermal equilibrium

Back 9

it's when two objects reach the same temperature and no heat flows between them.

Front 10

what does the amount of heat transferred depend on?

Back 10

the mass and kind of substance

Front 11

calorie

Back 11

the amount of heat needed to raise 1 gram of water 1 degree Celsius

Front 12

Specific Heat

Back 12

the measure of how much heat is required to raise the temperature of 1 gram of substance 1 degree Celsius

Front 13

What does thermal expansion depend on?

Back 13

the amount of temperature change and the identity of the substance

Front 14

Latent Heat:
When heat is being used to change phase, addition or removal of heat does not cause a temperature change.

Back 14

Q=mL
for water:
Lf=3.35x10^5 J/kg
Lv=2.26x10^6 J/kg

Front 15

Convection

Back 15

heat is carried from place to place by movement of a fluid

Front 16

Conduction

Back 16

Heat is transferred through the material without the motion of material

Front 17

Q

Back 17

it's proportional to
1) the length of conduction time. More time, more heat flow
2) The change in Temperature. The larger the temperature difference, the more heat that flows.
3) The cross sectional area A
4) The thermal conductivity (k) of the material
5) Inversely proportional to the length-thickness (L)
Q=(kA(delta)T)t/L

Front 18

Radiation

Back 18

-Energy is transferred by means of Electromagnetic waves.
-All objects radiate energy in the form of EM. HOtter objects radiate higher frequencies than colder ones

Front 19

Pressure of an ideal gas

Back 19

The pressure (P) is the magnitude of the force (F) acting perpendicular to a surface divided by the area (A) over which the force acts.
P=F/A
atm pressure=1.01x10^5 Pa
Pascal=N/m^2

Front 20

The Ideal Gas Law

Back 20

PV=nRT
R=8.31 J/(molxK)
Universal Gas Constant

Front 21

kinetic theory of gases

Back 21

KE=3/2kT
k=1.38x10^-23 J/K
Boltzmann's constant

Front 22

Internal energy of monatomic gases

Back 22

U=N(KE)

Front 23

Thermodynamics

Back 23

study of heat flow and how it caan be put to work

Front 24

Engines

Back 24

engines work by converting heat energy into mechanical energy, which can then do useful jobs (work) for us

Front 25

diathermal walls

Back 25

walls that permit heat flow

Front 26

adiabatic walls

Back 26

perfectly insulated walls

Front 27

The Zeroth law of Thermodynamics

Back 27

Two systems individually in thermal equilibrium with a third system, are in thermal equilibrium with each other
(Objects in thermodynamic equilibrium have the same temperature)

Front 28

First Law of Thermodynamics

Back 28

Whenever heat is added into a system, it transforms to an equal amount of some other form of energy
-internal energy increases (heat stays)
-it does external work (heat leaves the system)

Front 29

delta U

Back 29

the increase in the internal energy of the system

Front 30

delta Q

Back 30

heat energy supplied to thes ystem

Front 31

delta W

Back 31

the work done by the system

Front 32

First Law of thermodynamics equation

Back 32

delta U= Q-W
Q is positive when heat is added into the system
W is positive when the system does work on the surroundings

Front 33

The Four Thermodynamic Processes

Back 33

Isobaric
Isochoric
Isothermal
Adiabatic

Front 34

Isobaric Process

Back 34

-occurs at constant pressure
-V1/T1=V2/T2
-Some of the heat is used to increase the internal energy, the rest to do work.
W=P(delta)V

Front 35

Isovolumetric or Isochoric process

Back 35

-Occurs at constant volume
-P1/T1-P2/T2
-Since there is no change in volume, no work is done, so all heat entering the gas becomes internal energy.

Front 36

Isothermal Process

Back 36

-PV=constant and P1V1=P2V2
-(delta)U=0 because the internal energy is dependent on the temperature, which does not change.
-(delta)Q=(delta)W
-If the gas expands to do work, heat must also be supplied

Front 37

Adiabatic Process

Back 37

-a change where there is no heat flow in or out of a system is called adiabatic
-(delta)Q=0, therefore (delta)W=(delta)U

Front 38

When a gas undergoes changes that will eventually return to its original state, it will go through a cyclic processes

Back 38

a b

c d
-isochoric changes between a and b, and c and d
-isobaric changes between b and c, and d and a

Front 39

Internal Combustion Engine

Back 39

intake, compression, ignition, exhaust

Front 40

2nd law of Thermodynamics

Back 40

heat will never of itself flow from a cold object to a hot object
-A heat engine is any device that uses heat to do work

Front 41

Efficiency

Back 41

Efficiency is defined as the ratio of the work W done by the heat engine to the input heat Q(sub)H
e=Work done/Input heat
According to the Conservation of Energy:
Q(sub)H=W+Q(sub)C
e= (QsubH-QsubC)/QsubH
=1-QsubC/QsubH

Front 42

When does a heat engine have maximum efficiency?

Back 42

When the processes within the engine are reversible

Front 43

Reversible process

Back 43

A process in which both the system and its surroundings can be returned to their initial states
-all spontaneous processes are reversible
-No real engine can be reversible, but Carnot sets the highest standard

Front 44

What does efficiency depend on?

Back 44

TsubH and TsubC