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A Level Physics > Thermal Physics > Flashcards

Thermal Physics Flashcards

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1
Q

What is a thermal equilibrium?

A

It is a condition when two or more objects in contact have the same temperatures so there is no net flow of energy between them.

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2
Q

What is the basis of temperature measurements and what are some examples?

A

Any physical property that varies with temperature.

  • Change in volume of a liquid or gas
  • Change in pressure of a gas
  • Change in electrical resistance
  • Change in e.m.f of a thermocouple
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3
Q

What are the Qualities does a physical property need if it is to be used to measure temperature change?

A
  1. The change in the property should be large enough to be measured
  2. Value of the temperature recorded should be reproducible
  3. Property being used must be suitable over a range of temperature ranges being measured.
  4. Should change uniformly with temperature.
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4
Q

What is the thermodynamic (Kelvin) scale?

A

theoretical scale that is independent of the properties of any particular substance.

It is based on the idea that the average KE of particles in a substance will increase with increasing temperature.

The Kinetic energy is the same for all substances at a particular temperature.

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5
Q

what is absolute 0?

A

The temperature at which a system has minimum kinetic energy - at 0 kelvin.

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6
Q

What is the triple point of pure water?

A

The temperature at which water exists as vapour, liquid and solid at 273.16 Kelvin - 0.01 C

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7
Q

What are the advantages of a thermistor?

A
  1. Very Robust
  2. Fast Response
  3. Accurate
  4. Sensitive at low temperatures
  5. Reading can be taken remotely
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8
Q

What are the advantages of a thermocouple?

A
  1. Faster response
  2. Wider Range
  3. Small thermal capacity
  4. Physically small - readings are taken at point
  5. Power supply is not needed
  6. Reading can be taken remotely
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9
Q

what are some disadvantages with temperature?

A
  1. Non-linear temperature variation
  2. Narrower Range
  3. Slower response time than a thermocouple
  4. Larger than the thermal capacity
  5. Larger in size
  6. Not suitable to measure varying temperature
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10
Q

what are some disadvantages of thermocouples?

A
  1. Non-linear temperature variation

2. For an accurate reading, a high resistance voltmeter is required.

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11
Q

Explain how melting and boiling can occur without any change in the temperature.

A
  1. Temperature is a measure of random KE of particles
  2. At a phase transition, all energy is used to break bonds
  3. No change in KE occurs so the temp does not change.
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12
Q

Explain the cooling effect of evaporation.

A
  1. Particles that escape are those with higher velocity
  2. So the average KE of remaining substances decreases
  3. The temperature is the average KE
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13
Q

What is specific heat capacity?

A

It is the energy required per unit mass of the substance to raise the temperature by 1 Kelvin.

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14
Q

What is the formula for specific heat capacity?

A

E = mc(delta)(theta)

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15
Q

What are the quantities required when determining specific heat capacity?

A
  1. Accurate measurements of mass
  2. Temperature at time intervals
  3. Voltage and current supplied
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16
Q

What is the procedure and analysis leading to finding the specific heat capacity?

A
  1. Measure temperature at regular time intervals and plot a graph of temperature (theta) against time (t)
  2. E/t = mc (theta/t)
    E/t = P = VI
    theta/t = gradient
  3. substitute values and find c
17
Q

What is specific latent heat?

A

It is the energy required per unit mass of a substance to change it from solid to liquid phase without any change in temperature.

18
Q

What is the specific latent heat of vaporization?

A

It is the energy required per unit mass of a substance to change from liquid to gas phase without any change in temperature.

E = mL

19
Q

Why is the specific latent heat of fusion greater than the specific heat capacity?

A
  1. During vaporization, a greater increase in volume than infusion; thus more work is done against the atmosphere
  2. In vaporization, particles need to be separated further apart then in fusion so more work is done against forces of attraction.
20
Q

What are the quantities required to be measured when determining specific heat capacity?

A
  1. Mass at time intervals
  2. Beaker containing water heated to 100 C and maintained
  3. Mass reading is taken at regular intervals
21
Q

What is the procedure and analysis leading to the determination of specific heat capacity?

A
  1. Plot a graph of m against t
  2. l = (E/T)/(m/t) = (VI)/(m/t)
  3. m/t is the gradient
  4. substitute and find.
22
Q

What is internal energy?

A

It is the sum of the random distribution of kinetic and potential energies of molecules in a system.
I.E = P.E + K.E

23
Q

What is the first law of thermodynamics?

A

The increase in the internal energy of a system is equal to the heat supplied to the system and the work done on the system.

(delta U) = q +w

A Level Physics (16 decks)

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