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Module 5- Newtonian world and astrophysics > 5.1 Thermal physics > Flashcards

5.1 Thermal physics Flashcards

1
Q

What is a absolute or thermodynamic scale of temperature?

A

An absolute or thermodynamic scale of temperature is independent of the properties of any specific substance. Measured in Kelvin, K.

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2
Q

What is absolute 0?

A

(0 K) Is the temperature at which a substance has minimum internal energy; this is the lowest limit for temperature.

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3
Q

What is thermal equilibrium?

A

Objects in contact with each other at the same temperature are in thermal equilibrium; this means that there is no net heat flow between them.

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4
Q

Define temperature.

A

Temperature is a measure of how hot or cold an object is.

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5
Q

What does temperature measure?

A

Temperature only measures the kinetic energy component of an objects total internal energy.

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6
Q

Describe the total energy of a lit sparkler i terms of its temperature and thermal energy.

A

A lit sparkler has high temperature but can only transfer a small amount of thermal energy. The particles in the sparkler each have a lot of energy but there are few particles preset so the total energy is low.

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7
Q

Describe the total energy of a water i the North sea in terms of its temperature and thermal energy.

A

The water in the north sea is cold. It has a low temperature. However, the ocean stores much more thermal energy than a lit sparkler due to its mass (number of particles).

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8
Q

Describe the total energy of the sun in terms of its temperature and thermal energy.

A

The sun has a high temperature and due to its large mass, also has a large amount of thermal energy.

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9
Q

Who proposed the absolute scale of temperature?

A

Lord Kelvin.

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10
Q

How is Celsius and Kelvin related?

A

0 K is about -273°C so to work out Kelvin from Celsius, add 273 away.

T(K) = θ(°C) + 273

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11
Q

What is the value for absolute zero in Kelvin and Celsius?

A

Kelvin: 0K Celsius:-273°C

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12
Q

What is the value for the triple point of water in Kelvin and Celsius?

A

Kelvin: 273K Celsius: 0.01°C

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13
Q

What is the value for typical room temperature in Kelvin and Celsius?

A

Kelvin: 293K Celsius: 20°C

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14
Q

What is the value for steam point in Kelvin and Celsius?

A

Kelvin: 373K Celsius: 100°C

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15
Q

How is thermal energy always transferred?

A

Thermal energy is always transferred from areas of higher to regions of lower temperature.

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16
Q

If there is no temperature difference in objects in contact with each other, how can we describe them?

A

They’re in thermal equilibrium.

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17
Q

What is the kinetic model of matter?

A

In the kinetic model of matter all matter is made up of very small particles (atoms/ molecules/ ions) which are in constant motion. The model allows us to explain the properties of matter and changes of phase in terms of the arrangement of the particles, the motion of the particles and the attractive forces between them.

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18
Q

Use the kinetic model of matter to describe a solid.

A

Particles are close together and vibrate around their individual fixed positions in the lattice. Due to close proximity of the particles, they’re held together by strong forces of attraction, Solids generally have a high density and a definite shape.

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19
Q

Use the kinetic model of matter to describe a liquid.

A

Particles cannot move much but they can slide past one another. Their mean separation is greater than in solids and the attractive forces between them are weaker. Liquids generally have a lower densities than solids, can flow and can be poured.

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20
Q

Use the kinetic model of matter to describe a gas.

A

Contains particles that are free to move about, very quickly, in random directions. The forces of attraction between individual particles is very weak due to their high separation. They have low densities and can be compressed easily.

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21
Q

How can you work of the density of a substance in kg/cubic metres?

A

Density (kgm-3) = mass of one molecule x number of molecules per cubic metres.

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22
Q

What does the changing of phase require?

A

Changing of phases requires either an output of energy or a removal of energy.

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23
Q

When a substance is heated, is can turn from a solid to a liquid. What causes this?

A

This is due to the energy of the particles increasing as the energy is supplied. This extra energy results in the particles moving further apart until they have enough energy to overcome the forces of attraction to their adjacent particles.

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24
Q

When a substance is cooled, it can change from a liquid to a solid. What causes this?

A

Removing thermal energy from a system will reduce the amount of energy each particle has, causing them to move closer together, leading to condensation, and freezing.

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25
Q

Define internal energy?

A

The sum of the randomly distributed kinetic and potential energies of all the atoms or molecules within a system.

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26
Q

What factors impact a substances kinetic energy?

A

The substances mass and velocity of the particles.

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27
Q

Where is the p9otential energy of a system stored?

A

The potential energy of a system is stored in the bonds and intermolecular forces that exist between the particles.

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28
Q

When will the potential energy of a system be released?

A

The stored energy will be released when the attractive forces between the particles are overcome, such as during melting or evaporating.

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29
Q

When is the internal energy of a substance at it’s minimum?

A

When it is at absolute zero.

30
Q

What is the mean translational kinetic energy of the particles in a system proportional to?

A

The mean translational kinetic energy of the particles in a system is proportional to the absolute temperature, so the kinetic energy of the atoms in a system is at zero at absolute zero.

31
Q

When a substance is at absolute zero, is there any energy in the system?

A

There will be some potential energy due to the bonds between atoms.

32
Q

In a solid, what form is the kinetic energy in? What does this cause?

A

In a solid, the particles kinetic energy is in the form of vibrational motion, with the particles oscillating around a fixed point. This gives a varying kinetic energy.

33
Q

What does the total internal energy of a solid include?

A

The total internal energy will be the sum of the kinetic and potential energies of all the particles.

34
Q

What particles make up solids and liquids?

A

Molecules or ions.

35
Q

What is Brownian motion?

A
  1. Brownian motion is the random movement of small visible particles suspended in a fluid due to collisions with much smaller, randomly moving atoms or molecules of the fluid.
36
Q

When was Brownian motion first observed?

A

Brownian motion was first observed in 1827 by Robert Brown when he used a microscope to examine the particles inside pollen grains- he noticed that when they were in water the pollen grains were not still but moved about jerkily.

37
Q

Who explained Brownian motion?

A

Albert Einstein explained Brownian motion was caused by repeated bombardment by molecules of the water.

38
Q

What did Brownian motion first provide direct evidence of?

A

It showed evidence that atoms or molecules of a liquid or gas a constantly moving.

39
Q

How can you see Brownian motion in gas?

A

You can see smoke particles moving about randomly.

40
Q

What affect will occur when a particle showing Brownian motion has a large mass?

A

If the particles are too large, the increased mass of each particle means it changes it’s velocity less for each impulse and the movement will be harder to see.

41
Q

Describe the pattern of movement is a solid when heated?

A

When a solid is heated, it’s temperature will increase, and so it’s kinetic energy will increase. Because it is a solid, the positions of each atom will not change as they’re held i place by intermolecular forces.

Therefore, the increase of kinetic energy will result in greater vibration of the particles in their positions around their respective equilibrium positions.

42
Q

Describe the pattern of movement is a liquid when heated?

A

Similar to when a solid is heated, the particles experience an increase in vibrational kinetic energy- however, this time, they will also experience a small amount of translational kinetic energy added as the molecules can move past one another.

43
Q

Describe the pattern of movement is a gas when heated?

A

Particles in a gas will experience an increase of translational kinetic energy- in the form of linear motion- as the particles move from place to place, colliding with anything in their way.

44
Q

What sort of motion is associated with Brownian motion? (For example,the small of perfume will spread across a room)

A

Diffusion is often associated with Brownian motion.

45
Q

What is specific heat capasity?

A

The specific heat capacity, c, of a substance is the energy needed to raise the temperature of 1kg of a substance by 1K. (J kg-1K-1)

46
Q

What equation relates the the factors that affect the amount temperature increases or decreases?

A

E= mcΔθ

  • E= change in the thermal energy in J
  • m= mass of body in kg
  • c= specific heat capacity of the body in J kg-1K-1
  • Δθ= change in temperature in K or °C
47
Q

What is specific latent heat of fusion?

A

Specific latent heat of fusion is the amount of energy required to change the phase of 1kg of a substance from a solid to a liquid.

48
Q

What is specific latent heat of vaporasation?

A

Specific latent heat of fusion is the amount of energy required to change the phase of 1kg of a substance from a liquid to a gas.

49
Q

What is latent heat of vaporisation?

A

Specific latent heat of fusion is the amount of energy required to change the phase of 1kg of a substance from a liquid to a gas.

50
Q

What must happen for substance to change state?

A

In the substance forces of attraction between atoms, molecules or ions in the material must be overcome.

51
Q

To separate particles in a substance, what must be suppiled?

A

Energy, work done.

52
Q

How is energy transferred when a substance is changing phases from a gas to a liquid/ liquid to a solid?

A

Energy is taken from the material and released to the surroundings.

53
Q

What is the energy called that causes a change of phase?

A

Latent heat (hidden heat).

54
Q

How does a bodies mass affect the amount of latent heat required to change the materials phase?

A

The greater the mass of the body, the greater the quantity of the latent heat that will be required to change the materials phase.

55
Q

Why do we refer to an objects specific latent heat not it’s latent heat?

A

We refer the the specific latent heat to make calculations easier, as it refers to the energy required to change phase of 1kg of a specific material.

56
Q

What changes occurs to the internal energy during phase changes?

A

When a substance coinages phase the temperature remains constant so there is no increase in the kinetic energy of the atoms. This however, doesn’t mean their is no change in the internal energy, there is a change in the forces between molecules during a phase change which produces a change in their potential energy, so their internal energy can change even tho it’s kinetic energy is staying the same.

57
Q

What is the formula to work out the latent heat of a substance?

A

E = mL

  • E= Latent heat
  • m= Mass
  • L= Specific latent heat
58
Q

What does the the PAG to determine the specific latent heat of fusion set up look like?

A
59
Q

Describe the process of the PAG to determine the specific latent heat of fusion?

A
  • A known mass of ice is placed into 2 funnels .
  • The heater arrangement in A is connected to a power supply of a known power (so you can work out energy), while B (the control) is not connected to the power supply.
  • When water starts to drip from the funnels in to the beakers, the heater is switched on in beaker A.
  • After 15mins the heater is turned off and the mass of the water in both beaker is measured.
  • Mass in A will be greater than B, The differences in mass is equal to the mass of water that has been malted due to the electrical energy input.
  • You can then determine the specific latent heat of fusion with the equation: Lf= E/Δm
60
Q

What is a mole?

A

One mole of any substance is the amount of substance that contains as many particles as exactly 12.0g of carbon-12. One mole will contain 6.02x1023 particles (Avogadro’s constant).

61
Q

What is Avogadro’s constant?

A

6.02x1023 particles- the number of particles in a mole.

62
Q

What is the mass of one mole of a substances called?

A

It’s molar mass.

63
Q

Is the atomic mass on the periodic table the number that appears above or below the element symbol?

A

Above.

64
Q

If a doctor places a mercury-in-glass thermometer under a patients tongue, why must they leave it there a minute till they take a reading?

A

The temperature of the patient’s mouth and the temperature of the liquid in the thermometer will initially be different. When the thermometer and the patient’s mouth are in contact with each other, energy will be transferred between them until they are at the same temperature (thermal equilibrium). The temperature reading will not be accurate until this point.

65
Q

What is meant by the word thermal equilibrium?

A

Thermal equilibrium occurs when two objects in contact with each other are at the same temperature and there is no net energy transfer between them.

66
Q

If cold milk is added to hot tea, with reference to the molecules in the 2 liquids, how is thermal equilibrium reached?

A

The molecules in each liquid are moving: they have kinetic energy. The molecules in the hot tea have greater kinetic energy than the molecules in the cold milk, so energy is transferred from molecules of the hot liquid to molecules of the colder liquid. The temperature of the hot liquid decreases and the temperature of the cold liquid increases. Thermal equilibrium is reached when there is no net energy transfer between the molecules of the two liquids – both liquids are at the same temperature.

67
Q

When estimating a temperature change when 2 objects with different temperatures are added together, what do you have to make sure to consider?

A

Their masses.

68
Q

What is the first law of thermodynamics?

A

The increase of thermal energy of a system is equal to the heat added to the system minus the work done by the system.

Change of internal energy= eat energy gained/ lost in surroundings - work done on system

UΔ= ΔQ -ΔW

69
Q

What is the second law of thermodynamics? What does this mean referring to the flow of heat?

A

The total entropy can only increase over time for an isolated system. Therefore the net flow of thermal energy is always hot to cold.

70
Q

Define the word entropy.

A

Entropy- how disordered a system is.

Module 5- Newtonian world and astrophysics (5 decks)

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