Thermal physics Flashcards Preview

13 old > Thermal physics > Flashcards

Flashcards in Thermal physics Deck (47)
Loading flashcards...
1

Define internal energy

Sum of the individual potential and kinetic energies of all molecules within the body

2

State the first law of thermodynamics

The change of internal energy of the object is equal to the total energy transfer due to work done and heating

3

Define specific heat capacity

The energy required to change the temperature of 1kg of the substance by 1K without changing state

4

Describe the experiment to measure the specific heat capacity of a metal

Metal block of known mass in an insulated container. Electrical heater inserted into a hole in the metal, thermometer into another.
Measure the temperature change over a given time

5

Which measurements are used to measure specific heat capacity of a metal, and how?

Heater's current (I)
Heater's pd (V)
Time of heating (t)
Temperature change (ΔT)
mcΔT=IVt (rearrange for c)

6

State Boyle's law

When a fixed mass of gas is reduced in volume by a compressing piston, the pressure inside the piston increases

7

Explain why Boyle's law is true

Gas particles all in motion
Pressure exists from surface collisions exerting a force
Volume decreases
Collisions occur more frequently
Pressure increases

8

State Charles' law

For a fixed mass of an ideal gas at constant pressure, its volume is directly proportional to its absolute temperature

9

State the pressure law

For a fixed mass of an ideal gas at constant volume, its pressure is directly proportional to its absolute temperature

10

Define Avogadro constant

The number of atoms in exactly 12g of carbon-12

11

Define molar mass

The mass of 1 mol of the substance

12

What are the five assumptions that are made for the kinetic theory equation?

Molecules are point molecules
No attractive forces between molecules
Molecules move in continual random motion
All collisions are elastic
Time of collisions is negligible

13

Define molar heat capacity

The energy required to change 1 mol of gas by 1K

14

Define heat capacity

The energy required by an entire object to change temperature by 1K

15

How is work done on a gas calculated from a pressure against volume graph?

Area under the graph

16

Explain what is meant by specific latent heat of fusion (2)

The energy required to change one kg of an object from liquid to solid without changing temperature

17

Water is pumped througha heater in a hot tub, why is the temperature rise greater when the pump works at a higher speed? (2)

The pump is doing work on the water. Work can raise the temperature of the body

18

Use the kinetic theory of gases to explain why the pressure inside a football increases when the temperature of the air inside it rises. Assuming volume remains constant (3)

Molecules have a greater rms velocity. Number of collisions between molecules and inside surface of ball increases per second. pressure = F/A and F = rate of change of momentum

19

What is the equation for Work Done in a Piston with a set mass of gas in?

A: W = p ΔV W = Work Done p = Pressure ΔV = Change in Volume

20

What is the Second Law of Thermodynamics?

It is not possible to convert heat continuously into work, without at the same time, transferring some heat from a warm body into a cold body. : the total entropy of a system can never decrease over time (temperature of an object always wants to be in equilibrium with surroundings).

21

What is the equation for Force?

F = p x A F = Force p = Pressure A = Cross-Sectional Area

22

What is the equation for internal energy for constant pressure processes?

ΔU = ΔQ – pΔV ΔU = Change in Internal Energy ΔQ = Change in amount of heat supplied to the system p = Pressure ΔV = Change in Volume

23

What does the p-V graph look like for constant pressure (isobaric process)?

Horizontal line

24

What does the area below a p-V graph show?

Work Done

25

What are the rules for a cycle process?

1) For a complete cycle, ΔU = 0 (No change in internal energy)
2) the net work done = area enclosed by the cycle

26

How do you change from Celsius into Kelvin?

Celsius Temperature + 273

27

What is specific latent heat?

The amount of thermal energy required to change the state of 1 kg of a substance at constant temperature

28

What are the three equations for an ideal gas?

pV = NkT pV = nRT pV = (1/3)Nmc²

29

What are the equations for average kinetic energy?

KE = (1/2)m c² = (3/2)kT = (3/2)(RT/Nₐ)

30

What is the main property of a gas at absolute zero?

It has minimum internal energy