Physics Thermal Energy

Front 1

What do the symbols stand for and what are their units in the equation?

Q=mcAT (delta T)

Back 1

Q = Energy in Joules (J)

m = Mass in Kilograms (kg)

c = Specific heat capacity ( J/Kg C )

AT = Temperature change (*C)

Front 2

1. How do you change from Degrees to Kelvin?

2. How do you change from Kelvin to Degrees?

Back 2

1. add 273

2. subtract 273

Front 3

What is the definition of Specific Heat

Capacity?

Back 3

The specific heat capacity of a material is the energy required to heat a 1kg material through a temperature change of 1*C.

Front 4

What is an ideal gas?

Back 4

A gas that has no potential energy between particles therefore the internal energy is equal to the kinetic energy.

Front 5

What is Internal Energy?

Back 5

Internal energy is the sum of the kinetic and

potential energy of the particles that form the system.

U = Ek + Ep

Internal energy is randomly distributed

Front 6

Temperature:

If the average kinetic energy of the molecules of a substance increase, then it has a higher temperature.

What determines the temperature?

Back 6

The internal energy

Front 7

What is the first law of thermodynamics?

Back 7

The energy of the universe is constant.

Energy can be transferred from the system to the surroundings or vice versa, but never destroyed.

Euni = Esys + Esurr

Front 8

The first law of thermodynamics also shows that the internal energy is the sum of the heat gained or lost by the system and the work done on or by the system.

What equation represents this?

Back 8

Esys = Q + W

Front 9

Example of the first law of thermodynamics: beaker of water on a hot plate

-Hot plate is turnedon
-System gains heat from its surroundings
-Temp & internal energy of the system increase
-E is positive

Back 9

-When the hot plate is turned off
-Water loses heat to surroundings as it cools
-E is negative

Front 10

Relationship between internal energy and work can be understood byconsidering the tungsten filament inside a light bulb:
-Workis done on this system by driving an electric current through the tungsten wire
-System becomes hotter and E is therefore positive. (Eventually, the wire becomes hot enoughto glow.)

Back 10

Conversely, Eis negative when the system does work on its surroundings.

Front 11

internal energy&temperature of a system
decrease (E < 0):
-systemeither loses heat or
-does work on its surroundings

Back 11

internal energy&temperature of a system
increase (E> 0):
-system gains heat from its surroundings or -surroundings do workon the system

Front 12

Ideal Gas Equations:

pV = nRT

pV = NkT

What do the symbols R, N and k stand for?

Back 12

R = Universal Gas Constant (8.31 J/Kg mol)

k = Boltzman Constant (1.38x10-23 J/K)

N = Number of molecules

Front 13

Molecular Kinetic Energy:

1/2m<c^2> = 3/2kT

Back 13

Temperature must be measured in Kelvin

Front 14

What 3 things does the specific heat capacity depend on?

Back 14

1. Amount of heat energy transferred

2. The mass of an object

3. The material which the object is made of

Front 15

The Maxwell-Boltzmanndistribution shows how many particles in a gas have the differentspeeds.

If you plot a graph of speed distribution against speed for a gas of two different temperatures, what can you conclude?

Back 15

1. At a higher temperature the average speed
increases.

2. At a higher temperature the maximum speed increases.

3. At a higher temperature the distribution of speeds is greater.

Front 16

Boyle's Gas Law:

The pressure of a given mass of an ideal gas is inversely proportional to its volume

Only if the temperature is constant

Back 16

p & 1/V

Front 17

Charles' Gas Law:

The volume of a given mass of an ideal gas is directly proportional to the temperature

Only if the pressure is constant

Back 17

V & T (kelvins)

Front 18

Pressure Law:

For a given mass of an ideal gas, the pressure is directly proportional to the temperature

Only if the volume is constant

Back 18

p & T (kelvins)

Front 19

What assumptions are made for an ideal gas?

Back 19

1. The gas consists of a large numberof
identical molecules
2. The molecules obey Newton's laws
3. The volume of the molecules is negligibly small comparedto the volume occupied by the gas
4. No forces act on themolecules except during elastic collisions of negligible duration.