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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

Study These Flashcards
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

Study These Flashcards
A

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

25
How can the internal energy of a system change?
Either when the energy is transferred by heating or by doing work
26
What is an example of an isothermal process?
Heating up boiling water
27
Explain why heating up boiling water is an isothermal process?
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
What is an example of an adiabatic process?
Aerosol can
29
Explain why the aerosol can is an adiabatic process?
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
What is a heat pump?
A heat pump transfers heat energy from a cooler object to a hotter object by using energy
31
What does a refrigerator do?
Removes heat from inside the fridge by transferring it to the air surrounding the fridge by the expansion and compression of a coolant
32
Turn 25•c into K
25+273=298 k
33
Turn 780k into •c
780-273=507•c
34
What are two equations for efficiency
Efficiency= 1- Qout/Qin Efficiency= 1-Tc/Th
35
Step 1 of petrol engine
Intake: fuel and air mixture taken into piston
36
Step 2 of petrol engine
Compression: the mixture is compressed adiabatically which decreases volume and increases pressure
37
Step 3 of petrol engine
Ignition: the mixture is ignited and this causes large change in Temperature and pressure and no change in volume
38
Step 4 of petrol engine
Expansion: the gas is expanded adiabatically and does work by pushing piston down. The volume increases and pressure decreases
39
Step 5 of petrol engine
Exhaust: the piston is opened which decreases the pressure. The gas leaves the piston which decreases volume
40
State of ice
Molecules are close together and vibrate in a fixed position. The intermolecular forces are strong
41
State of water
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
States of steam
Molecules are far apart and able to move freely. Almost no intermolecular forces between molecules
43
In molecules as the energy increases…
The temperature increases
44
In a solid (ice) state there is less…
Kinetic energy
45
In a gas (steam) state there is more…
Kinetic energy
46
When increasing temperature, the ice…
Has strong intermolecular forces and when temperature increases the molecules gain more energy and vibrate more
47
When increasing temperature, in the melting stage…
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
When increasing temperature, in the liquid state…
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
When increasing temperature, in boiling…
The energy of the molecules remains constant and the energy is transferred to the water to break the intermolecular attractions (water to steam)
50
When increasing temperature, in steam…
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
What is the specific latent heat of vaporisation?
The amount of energy needed to boil (vaporise) 1 kg of water
52
What equation can be used with specific latent heat of vaporisation
Q=delta m x L
53
Specific heat capacity equation
Q=M C delta T
54
Equation when calculating M for specific heat capacity
M=Q/ Cxdelta T
55
Equation for when calculating delta T in specific heat capacity
Delta T= Q/mc
56
What is thermal equilibrium
This is when the energy flowing in is equal to the energy flowing out and the temperature stops increasing (reaches its maximum)
57
What’s is the thermal capacity of an object
How much energy is needed to increase the temperature of the object by 1K

Physics (3 decks)

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