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Physics CIE > Thermal Physics > Flashcards

Thermal Physics Flashcards

(77 cards)

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1
Q

What does the kinetic molecular model state?

A

That everything is made up of lots of tiny identical molecules

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2
Q

Solid properties

A

Very close together and fixed regular arrangement. Can’t move past each other, only vibrate. Low energy. Very strong bonds.

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3
Q

Liquid properties

A

Molecules are close together, can move past each other, irregular arrangements. Weaker bonds than solid but more energy. Move around each other in random directions at low speeds.

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4
Q

Gas properties

A

Far apart. High energy. Move in random directions at high speeds. Molecules move freely so almost no forces between molecules.

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5
Q

How does shape and flow affect states of matter?

A

Solid: can’t flow. Fixed size and shape. Can’t move past each other because of strong bonds.
Liquids and gases: can flow. Take shape of container they’re in. Molecules can move past each other.

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6
Q

How does compressibility affect states of matter?

A

Gases can be compressed. Liquids and solids cannot. Because gas molecules are far apart so it can be pushed closer together. Liquids and solids are already so close together they can’t be pushed closer.

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7
Q

How does volume affect states of matter?

A

Solids and liquids have a fixed volume. Gas is expand to have the same volume as their container. This is because strong bonds between solids and liquids to keep the molecules close together, gases have almost no forces between molecules.

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8
Q

How does density affect states of matter?

A

Solids are more dense than liquids generally, and liquids generally more dense than gases. Distances between the molecules and a liquid are larger than in a solid, so there is less mass per unit volume. Same in terms of gas and liquid.

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9
Q

How do particles suspended in afluid move?

A

In random directions

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10
Q

What is the term for particles mixed throughout the fluid?

A

Suspended

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11
Q

How do solids suspended in liquids move?

A

In zigzag paths in random directions. Can move even if fluid is not.

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12
Q

How does brownian motion provide evidence for the molecular model?

A

Molecular model states fluid is made up of many small molecules that you can’t see. When larger molecules are suspended in the fluid, they collide. The collision changes the speed and direction of larger particles moving them in random directions.

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13
Q

How does brownian motion work with changing momentum?

A

Small light fluid molecules are able to move a solid particle more massive than themselves, because they have a large speed and relatively large momentum therefore. When they collide, they undergo a large change of momentum, applying a large force which causes the particle to move.

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14
Q

What happens when gas molecules collide with container walls?

A

A force is exerted on the walls creating pressure

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15
Q

What is gas pressure?

A

The total force exerted by all the molecules in the gas on a unit area of the container walls

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16
Q

How does momentum work with gas pressure?

A

When a molecule collide with a wall, it rebounds and changes direction, changing momentum. The wall exerts a force to change momentum, and moleucle applies equal and opposite force. The faster a molecule travels during a collision, the larger the momentum change and larger the force exerted.

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17
Q

At a constant volume, how does gas pressure relate to temperature? And why

A

Gas pressure will increase with temperature, because molecules move faster, so the total force exerted on the wall will increase, pressure is force per unit area so pressure will be higher.

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18
Q
A
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19
Q

At a constant temperature, how does the volume affect gas pressure? And why

A

Decreasing volume will increase pressure, because the gas molecules have less room to move so there are more often collisions with container walls, greater overall force say greater pressure increases

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20
Q

Equation in terms of pressure and volume

A

pV = constant

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21
Q

How does heating a substance relate to internal energy?

A

When you heat a substance, you increase its internal energy

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22
Q

What is the temperature of a substance?

A

A measure of the average kinetic energy of its molecules

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23
Q

What is internal energy?

A

The total energy of the molecules in a substance

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24
Q

What happens when energy is supplied by heating?

A

Either:
The energy will be transferred to the kinetic energy of the molecules meaning the temperature of the substance will increase
The energy will be used to change the state of the substance . It breaks or weakens the bonds between molecules.

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25
What happens when a substance changes state?
Energy is transferred.
26
Why does a substance not change temperature when it is changing state?
Because the internal energy will change, but the kinetic energy of the molecules will not
27
Why do substances condense or solidify when molecules lose energy?
A substances cool energy is transferred away, so internal energy decreases. the molecules move closer together, so forces between molecules become stronger.
28
What is the difference between evaporation and boiling?
In boiling bubbles of gas form throughout the liquid and rise to the surface, evaporation individual molecules escape from the surface. Boiling occurs at the boiling point and evaporation occurs below the boiling point
29
In evaporation, when can molecules escape?
If they’re travelling in the right direction, and if they have enough kinetic energy to overcome the attractive forces of other molecules in the liquid.
30
How does temperature affect evaporation?
The higher the temperature, the higher the average kinetic energy so molecules have enough kinetic energy to escape
31
How does surface area affect evaporation?
The largest surface area at the more molecules near the surface and in the correct position, so will be able to escape
32
How does draught affect evaporation?
If the error is moving molecules that escape from the liquid wouldn’t be able to drop back into the liquid because they’ll be carried away so evaporation is more
33
Why does evaporation have a cooling effect?
The molecules that escape usually have the most kinetic energy, therefore the average kinetic energy decreases and so does the temperature.
34
How does sweating cool you down?
As the water from the sweat on your skin evaporates, energy from the skin in contact with the liquid transfers to the liquid so the skin cools down, therefore your body cools
35
What is the specific latent heat?
The amount of energy needed to change 1 kg of a substance from one state to another without changing its temperature
36
What is the latent heat of fusion?
The amount of energy needed to melt a substance
37
What do you call the amount of energy needed for a liquid to become a gas?
The latent heat of vaporisation
38
Specific latent heat word equation
Energy 🟰 mass ✖️ specific latent heat
39
Specific latent heat letters equation
Energy = ml
40
Specific latent heat unit
J/kg
41
What is the thermal capacity?
The internal energy needed to raise the temperature of a body by 1°C
42
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1 kg of a substance by 1°C
43
What does it mean by specific heat capacity being a material constant?
Any sample of a specific material will have the same specific heat capacity
44
Specific heat capacity equation
Change in energy = m x c x delta T, where c is SHC
45
Specific heat capacity unit
J/kg °C
46
What is the thermal capacity equation?
Thermal capacity = mc
47
Describe an experiment to measure specific heat capacity of a liquid
1. Use a mass balance to measure the mass of an insulating container, filled with water and measure the new mass. Difference in mass is mass of liquid. 2. Place a lead on insulating container to minimise energy transferred and stop liquid evaporating. 3. Measure initial temperature of liquid then turn on an electric immersion heater. Make sure power is low. 4. When liquids temperature has increased by 10° C switch of power and record temperature increase and energy transferred to the liquid from a joulemeter. 5. Calculate specific heat capacity by rearranging equation. 6. Repeat experiment five times then find average SHC.
48
Describe an experiment to measure specific heat capacity in solids
1. You need a block of the material with two holes in it for the heater and thermometer. 2. Measure the mass. 3. Heat the material on a low power mode until it has increased by 10° C. 4. Record the temperature increase and energy transferred to liquid. 5. Workout specific heat capacity and repeat to find an average.
49
What happens in thermal expansion?
When substances are heated, they get bigger, for every state of matter as long as surrounding pressure isn’t changing
50
Why does formal expansion happen?
The molecules in the substance gain energy and move away from each other. Amount a substance expands depends on forces of attraction between molecules.
51
Which state expands the least of all states of matter and why?
Solids because they have the strongest forces so molecules can’t move very far apart even when gaining energy.
52
How do rivets use formal expansion?
If you heat a metal rod, it will get longer A very hot metal rod is threaded through holes in plates. It is then hammered down so it ends are flat against the surfaces. as it cools down its length decreases so the flattened ends of the rivet pull the two plates together tightly.
53
Why can you loosen the lid of a jar by running it under hot water?
When a solid ring is heated it undergoes thermal expansion. The ring itself gets bigger and so does the gap in the centre. When running a jar under hot water, the lid heats up and expands increasing the diameter of the lid making it easier to remove.
54
How do expansion joints work?
They fastened pieces of a bridge of building together while leaving a small gap where the pieces meet then when the bridge or building gets hot, it can expand into the gap without causing damage.
55
Why are powerlines made to be slightly saggy?
Because if they contract in the cold, they could snap or damage the pylons
56
How do you liquid in glass thermometers WORK?
When the bulb is placed on into the substance being measured, and the substance is hotter than the thermometer, the liquid in the reservoir heat and expands causing the liquid to rise up the capillary tube. The same happens when the liquid cools down.
57
How do you set thermometer scales?
Using fixed points. These are observable phenomena that always occur at a particular temperature. E.g: water freezes at 0° C and boils at 100° C. A liquid and glass thermometer is linear so you can divide the distance into 100 equally spaced goodbye yellow steps.
58
What are the three types of thermal energy transfer?
Conduction, convection, radiation
59
True or false? not every object absorbs and emits infrared radiation
False. All of that are continually emitting and absorbing infrared radiation, from their surfaces.
60
How does infrared work with a hotter object?
A hotter object emits more infrared radiation than it absorbs. Therefore more thermal energy is transferred away so it cools down.
61
How do colours affect radiation emission?
Black surfaces are better at absorbing and emitting radiation than a white one
62
How do surfaces affect radiation?
A dull surface is better absorbing and emitting radiation than a shiny one
63
How does temperature affect infrared emission?
The higher the surface temperature, the more infrared radiation emitted
64
How does surface area affect infrared emission?
The bigger the surface area, the more infrared waves that can be emitted so the higher the rate of energy transfer.
65
What are fins and how do they work?
Thin flat parts that have a large surface area, they helped to increase the total surface area over which a device can emit radiation to maximise the rate of thermal energy transfer away from the device.
66
How do you investigate a mission of the Leslie cube?
Place a Leslie cube on a heat proof mat Boil water and a kettle and fill the cube with boiling water Wait for the cube to warm up, then hold a thermometer against each of the four vertical faces Each face should be the same temp Hold an infrared detector, a set distance away from one face and record the amount of infrared radiation . Repeat for each face. You should find that more infrared radiation is detected from the black and match surfaces rather than white and shiny ones
67
What is a Leslie cube?
A hollow watertight cube made of metal. It has four vertical faces with different surfaces E.G black paint white paint, shiny metal and dull metal.
68
What is conduction?
A type of thermal energy transfer where energy is transferred through a material. Energy spread out from the point where the object is heated into the whole object is warmer.
69
What does a good thermal conducter do?
Transfer energy very quickly. Liquids and gases are poor thermal conductors.
70
What type of solid are good thermal conductors?
Metals
71
Describe an experiment to demonstrate conduction
1. Attach identical feeds at regular intervals to 1/2 of a long metal rod using identical blobs of wax. 2. Hold the rod horizontally in a clamp stand. Using a button hit the side of the rod with no beads attached. 3. As time goes on energy is transferred along the road by conduction and the temperature increases. 4. As the temperature increases the wax holding the bead will gradually melt and the beads will fall starting with the beard closest to the point of heating.
72
What is conduction definition?
Conduction is the price software vibrating particles transfer kinetic energy to the neighbouring particles
73
How does conduction work?
In a solid the molecules are held tightly together so when one molecule vibrates that collide with other molecules nearby and the vibrations quickly passed from molecule to molecule. This process continues throughout the solid and gradually some of the energy is passed all the way through causing a rise and temperature at the other side.
74
Why do metals conduct heat well?
Because electrons are free to move inside the metal. At the hot end electrons move faster and collide of other three electrons transferring energy energy. Electrons can move freely so it’s obviously a much faster way of transferring energy instead of through vibrating neighbouring molecules.
75
Convection definition
The process were more energetic molecules of the substance move from a hotter region to a cooler region and transfer energy as they do
76
Describe the immersion heater example
1. Energy is transferred from the heater coils to the internal energy of the water by conduction. 2. The coil heats up and undergoes thermal expansion becoming less dense. 3. Hot water tends to rise above the den cooler water. 4. Cold water is then heated by the clothes and rises creating a convection current.
77
How can you use coloured crystals to see convection?
Place purple potassium permanganate crystals in a beaker of cold water. Using a Bunsen burner hit the side of the beaker with crystals at the bottom. As the temperature increases, they begin to dissolve forming a bright purple solution. The solution is carried through the water by convection tracing a path of the convection currents.

Physics CIE (5 decks)

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