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thermal physics Flashcards

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1
Q

what is work done

A

when a force moves an object and energy is transferred to the object. the greater the force and the greater distance moves then the more work is done

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2
Q

what is power

A

power is the amount of energy supplied (or work done) per second

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3
Q

what factors can affect the pressure exerted by gas

A

the volume of the container, the number of gas particles (moles) and the temperature of the gas.

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4
Q

what is the ideal gas equation

A

PV=nRT

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5
Q

make p the value

A

P=nRT/V

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6
Q

make v the value

A

V=nRT/P

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7
Q

make n the value

A

n=PV/RT

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8
Q

make t the value

A

T=PV/nR

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9
Q

what is the first law of thermodynamics

A

that energy can’t be made or destroyed just transferred from one form to another

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10
Q

what is internal energy

A

the sum of all energy of particles in a system (symbol=U)

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11
Q

internal energy equation

A

delta U= Q- W

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12
Q

what happens to the temperature if the internal energy increases

A

the temperature increases

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13
Q

what happens in an isothermal process

A

the temperature of the system remains constant

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14
Q

what is an adiabatic process

A

when no heat is transferred to or from the system

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15
Q

what is the second law of thermodynamics

A

that heat energy never flows spontaneously from the colder object to the hotter object

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16
Q

what happens in step one of removing heat from fridge

A

compressor= to compress the coolant vapor which heats up the coolant

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17
Q

step 2 of removing heat from fridge

A

condenser coils= to remove heat energy from the coolant by transferring it to the surroundings via conduction and radiation. there are metal coils to aid conduction and they are painted black to aid radiation

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18
Q

step 3 of removing heat from fridge

A

expansion devise= the liquid coolant expands and some become a vapor which decreases the temperature. expansion is an adiabatic process

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19
Q

step 4 of removing heat from fridge

A

evaporator coils= to remove heat from inside the fridge by transferring it to the coolant. the energy transferred to the coolant causes it to evaporate and turn into a vapor

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20
Q

Efficiency of compressor in fridge

A

Heats up when condensing the vapour which wastes energy and overall efficiency

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21
Q

Efficiency of condenser coils in fridge

A

•Efficiency of cooling and condensing vapour depends on the temperature difference between the coolant and surroundings
•Not all energy can be removed from coolant

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22
Q

Efficiency of expansion device

A

Almost 100% efficient

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23
Q

Efficiency of evaporator coils in fridge

A

Efficiency of cooling inside the fridge depends on how fast heat energy can be extracted from the fridge

24
Q

What do heat engines do

A

They transfer heat energy from hotter to colder objects and convert it into mechanical energy to do work

25
Q

How can the internal energy of a system change?

A

Either when the energy is transferred by heating or by doing work

26
Q

What is an example of an isothermal process?

A

Heating up boiling water

27
Q

Explain why heating up boiling water is an isothermal process?

A

The heat energy is transferred from the fire to the boiling water. Some water molecules are vaporised so need energy. The energy supplied from the fire is equal to the energy used to vaporise the water. Therefore the internal energy is constant (delta u= 0)

28
Q

What is an example of an adiabatic process?

A

Aerosol can

29
Q

Explain why the aerosol can is an adiabatic process?

A

The aerosol gas pushes the surrounding air and this requires energy so it uses the internal energy of the aerosol gas. This causes the aerosol to become cold when releasing the aerosol gas.
No heat was transferred from or to the system and only energy transferred was by work on surrounding air

30
Q

What is a heat pump?

A

A heat pump transfers heat energy from a cooler object to a hotter object by using energy

31
Q

What does a refrigerator do?

A

Removes heat from inside the fridge by transferring it to the air surrounding the fridge by the expansion and compression of a coolant

32
Q

Turn 25•c into K

A

25+273=298 k

33
Q

Turn 780k into •c

A

780-273=507•c

34
Q

What are two equations for efficiency

A

Efficiency= 1- Qout/Qin
Efficiency= 1-Tc/Th

35
Q

Step 1 of petrol engine

A

Intake: fuel and air mixture taken into piston

36
Q

Step 2 of petrol engine

A

Compression: the mixture is compressed adiabatically which decreases volume and increases pressure

37
Q

Step 3 of petrol engine

A

Ignition: the mixture is ignited and this causes large change in Temperature and pressure and no change in volume

38
Q

Step 4 of petrol engine

A

Expansion: the gas is expanded adiabatically and does work by pushing piston down. The volume increases and pressure decreases

39
Q

Step 5 of petrol engine

A

Exhaust: the piston is opened which decreases the pressure. The gas leaves the piston which decreases volume

40
Q

State of ice

A

Molecules are close together and vibrate in a fixed position. The intermolecular forces are strong

41
Q

State of water

A

The molecules are close to each other and are able to slide over each other. The intermolecular forces are weaker than ice but stronger than steam

42
Q

States of steam

A

Molecules are far apart and able to move freely. Almost no intermolecular forces between molecules

43
Q

In molecules as the energy increases…

A

The temperature increases

44
Q

In a solid (ice) state there is less…

A

Kinetic energy

45
Q

In a gas (steam) state there is more…

A

Kinetic energy

46
Q

When increasing temperature, the ice…

A

Has strong intermolecular forces and when temperature increases the molecules gain more energy and vibrate more

47
Q

When increasing temperature, in the melting stage…

A

The energy of the molecules stays constant and the energy is transferred to the ice to break the strong intermolecular attractions between molecules (ice to water)

48
Q

When increasing temperature, in the liquid state…

A

The intermolecular forces are weaker then in ice and melting. The molecules are able to slide over each other and the kinetic energy is increasing (move more)

49
Q

When increasing temperature, in boiling…

A

The energy of the molecules remains constant and the energy is transferred to the water to break the intermolecular attractions (water to steam)

50
Q

When increasing temperature, in steam…

A

There are almost no intermolecular forces, they have weakest intermolecular forces. The molecules are able to move freely and have most kinetic energy (moving faster)

51
Q

What is the specific latent heat of vaporisation?

A

The amount of energy needed to boil (vaporise) 1 kg of water

52
Q

What equation can be used with specific latent heat of vaporisation

A

Q=delta m x L

53
Q

Specific heat capacity equation

A

Q=M C delta T

54
Q

Equation when calculating M for specific heat capacity

A

M=Q/ Cxdelta T

55
Q

Equation for when calculating delta T in specific heat capacity

A

Delta T= Q/mc

56
Q

What is thermal equilibrium

A

This is when the energy flowing in is equal to the energy flowing out and the temperature stops increasing (reaches its maximum)

57
Q

What’s is the thermal capacity of an object

A

How much energy is needed to increase the temperature of the object by 1K

Physics (3 decks)

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