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Thermal Physics Flashcards

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1
Q

What factors affect how liquids evaporate?

A

Wind, temperature and surface area

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2
Q

How does wind affect evaporation?

A

When there is movement of air, the rate of evaporation is faster.

A certain amount of air can only mix with a certain amount of water vapour before it becomes full. Thus when the there’s a movement of air the initial chunk of air full of water gets replaced by new air, which takes in more water vapour.

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3
Q

How does temperature affect the rate of evaporation?

A

The kinetic energy of the molecules corresponds to the temperature the object has. The higher the temperature the faster the liquid molecules move. Thus the higher the temperature the larger the rate of evaporation.

Higher temperatures mean there is enough kinetic energy within the water for the molecules to escape. Increasing the evaporation rate.

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4
Q

How does surface area affect evaporation?

A

The higher the SA the higher the rate of evaporation.

This is due to more liquid being exposed to the air, which therefore makes the rate of evaporation higher

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5
Q

What is the difference between evaporation and boiling?

A

Evaporation: liquid to gas (surface effect)

Can happen at any temperature

Boiling: liquid to gas (occurs within the liquid)

Can onky happen at boiling temp

Energy imput without a change in temp

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6
Q

What does expansion mean?

A

The space between the particles increases. Therefore increasing the volume of particles.

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7
Q

What does contraction mean

A

Space between the particles decreases

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8
Q

How does the increase of heat affect the expansion of particles.

A

More heat = more expansion = more volume

This is due to the kinetic energy of the particles within the substance increasing, making the particles move at a faster rate. When the particles gain kinetic energy they become less and less rigged, increasing the space between the particles and therefore causing expansion.

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9
Q

What is the equation for sensitivity?

A

The change in property (how far the liquid moves up/down the thermometer, measured in mm)

Divided by

Change in temperature

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10
Q

How would you know there’s no change in sensitivity on a graph?

A

The gradient on a sensitivity graph would be a STRAIGHT LINE

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11
Q

How would you know there’s a change in sensitivity on a sensitivity graph

A

The gradient is CURVED

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12
Q

How would you calculate the gradient on a sensitivity graph which curves?

A

You would use a tangent

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13
Q

What are thermocouples

A

Thermocouples consist of two dissimilar electrical conductors forming an electrical junction. It produces a reading in volts which can be used to measure temperature.

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14
Q

What piece of evidence supports the idea of motions of atoms in fluids?

A

Brownian Motion

An experiment where you put soot particles against light. You can therefore see the movement of atoms across the soot particles. They look like little white sparkle ps

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15
Q

How does evaporation cause cooling?

A

When particles leave the surface of a liquid the kinetic energy decreases as there’s less collisions. Less kinetic energy causes lower temperatures. This therefore gives the sensation of being cold.

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16
Q

How could I make a thermometer more sensitive?

A

Decrease the size of the diameter of the cappillery (liquid will move up/down the thermometer at a faster rate)

Increase the size of the bulb (larger amounts of liquid mean the rate of expansion is larger)

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17
Q

What is thermal energy measured in?

A

Joules

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18
Q

What is meant by the term sensitivity?

A

If the thing you’re measuring changes significantly when the temperature changes, it makes it easier to detect small changes in temperature.

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19
Q

Heat moves from high energy particles to low particles. How would this affect your hands if you were to be holding ice?

A

Your hands would feel cold as heat would transfer from your hands to the ice. This is due to heat always travailing from hot to cold

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20
Q

What is the definition of conduction

A

Passing on increased vibrations of atoms “knock on effect”

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21
Q

How would you calculate the rate of cooling?

A

Change in temperature

Divided by

Amount of time the substance has been cooling for

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22
Q

To calculate the rate of cooling on a curved line you would need to do what

A

Draw a tangent as use that line to divide temperature change by time spent cooling

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23
Q

What is U-value

A

Known as thermal transmittance; it is the rate of transfer of heat through a 1m^2 structure for a 1C temp difference.

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24
Q

How does doubling the temp difference affect the u value of an object?

A

It doubles the u value

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25
Q

How does doubling the length of the sides of an object affect the u value of said object

A

You quadruple the u value

26
Q

What is the definition of convection?

A

The movement of heat through liquids and gasses (fluids).

27
Q

What is the process of convection?

A
  • particles gain kinetic energy
  • fluid expands (NOT PARTICLES!!)
  • particles separate out
28
Q

What does linear mean?

A

Same change of physical property for the same change of temperature.

29
Q

What is radiation?

A

A form of heat that can travel through vaccumes as it doesn’t require particles. It travels through mediums

30
Q

What is internal energy?

A

Internal energy is the energy of the particles themselves

31
Q

What is the equation for the total energy of the particles (internal energy)

A

Kinetic energy + potential energy

32
Q

What aspects affect emission of infra red radiation?

A

Colour, and shinyness

33
Q

What is an experiment to prove that colour and shiny ness of a surface have an impact of emitted infra red radiation?

A

Leslies cube

34
Q

Change in kinetic energy is inversely or directionally proportional to change in temperature?

A

Directionally proportional

35
Q

What happens to the potential energy of a liquid turning to a solid?

A

When a liquid turns into a solid the potential energy of the particles decreases. This is because the gaps between the particles becomes smaller making there less potential energy.

36
Q

When an object looses potential energy, what happens to the internal energy?

A

The amount of internal energy lowers.

37
Q

What does the term “melting point” mean?

A

The temperature at which a solid turns to a liquid whilst keeping a constant temperature.

38
Q

Is change in temperature directly or inversely proportional to change in thermal energy?

A

Directly proportional.

39
Q

Two blocks with different masses get heated for one minute. The change in temp is much greater in the smaller block then the larger block. Why is this?

A

The smaller block has less particles to share the thermal energy with so the average kinetic energy per particle (temperature) of the smaller block will be higher than the larger one.

40
Q

Two blocks with the same mass get applied different amounts of heat. Why would the block which receives more heat have a larger temperature rise?

A

More energy would be given to the particles with a large amount of thermal energy. Therefore the particles have more energy. This increases the kinetic energy and therefore increases the temperature change.

41
Q

Is change in temperature directly or inversely proportional to mass or an object?

A

Inversely proportional

42
Q

To find out spesific heat capacity we need to find a KONSTANT. What would be the equation to find out specific heat capacity?

A

K = Q/ (M X 0C)

43
Q

What equation can you use to find the thermal energy of something?

A

Q = I x V x t

Thermal Energy = Amps x Potential Difference x time

44
Q

Why would you need to add lagging whilst trying to find the spesific heat capacity of an object?

A

It prevents heat from conducting to its surroundings as heat always goes from hot to cold.

45
Q

What is internal energy?

A

The total kinetic and potential energy of the particles

46
Q

What if the definition of specific heat capacity?

A

Heat required to change the temperature of 1kg of material.

47
Q

What is spesific latent heat?

A

The heat required/emitted to change the STATE of 1kg of substances

There is also no visible temperature change present when the substance is changing state

48
Q

What is the formula for latent heat

A

Q/m = L

Thermal energy / mass = Latent heat

49
Q

When do we use Lv (Latent heat of vaporisation)?

A

When we’re going between a liquid and a gas.

50
Q

The definition of Latent Heat changes depending how the state is changing. For example, heat is REQUIRED when:

A

Solid to liquid

Liquid to gas

51
Q

The definition of Latent Heat changes depending how the state is changing. For example, heat is EMITTED when:

A

Liquid to solid

Gas to liquid

52
Q

What is latent heat?

A

Heat required/emitted to change the state of a substance.

53
Q

When do we use Lf (latent heat of fusion).

A

When going between liquid and solid

54
Q

What are the units for spesific heat capacity

A

J/(kg x 0C)

55
Q

What is the difference between heat and temperature?

A

Temperature change = Spesific heat capasity

Heat change = Latent heat

Heat is a form of energy. It is measured in Joules. It relates to kinetic energy which causes the particles in an object or substance to vibrate. … Temperature is the average kinetic energy of the particles in a substance.

56
Q

Why do you want to add lagging and protection for a spesific heat capasity experiment?

A

To reduce heat gain from surroundings

57
Q

Why is energy needed to boil water

A

Thermal energy gives internal energy (potential energy) to the particals. Thus making the water reach higher temperatures (boiling)

58
Q

What is evaporation?

A

The escape of more enegetic molecules from the surface of a liquid

59
Q

What are some characteristics of good thermal conductors.

A

haveing freely moving electrons that can transfer thermal energy quickly and easily.

60
Q

What are some characteristics of bad thermal conductors?

A

They have strong bonds that hold their particles rigidly in place.

61
Q

When do we use Lv (latent heat of vaperisation)

A

When going from liquid to gas.

Physics (4 decks)

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