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IGCSE Physics > Kinetic theory (Unit 2) > Flashcards

Kinetic theory (Unit 2) Flashcards

1
Q

Kinetic molecular model of a:
1-Solid
2-Liquid
3-Gas

A

1-Fixed shape and volume, with high density and won’t flow.

2-Takes the shape of bottom of the container it’s in, has a fixed volume, medium density and it flows.

3-Takes up the shape and volume of the container it’s in, has a low density and it flows.

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2
Q

Describe/explain Brownian Motion and give an example

A
  • Brownian motion is the random jerky motion of particles viewed through a microscope.
  • It’s caused by rapid collisions between moving invisible particles(molecules) and larger other particles. They collide then bounce off each other.
  • E.g. dust particles in the air or pollen grains in water.
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3
Q

Describe the movement of a particle in Brownian motion

A

Moves in a total long way (jerky moments) but doesn’t move far from the point in the center.

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4
Q

The space and attraction between molecules in:
1-Solids
2-Liquids
3-Gases

A

1-High forces and small spaces. Fixed shape.

2-Medium forces and small spaces. Random motion.

3-Very low forces and large spaces. Random motion of molecules.

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5
Q

Describe a short experiment to demonstrate evaporation

A

Put some ethanol onto the back of your hand. It feels a little cold and the ethanol evaporates off your hand. If you give it a blow it increases the rate at which the reaction occurs.

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6
Q

Evaporation increases when? (3)

A
  • Its warmer
  • Wind is supplied
  • A greater surface area
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7
Q

Boyle’s law

A
  • Pressure and volume are inversely proportional.
  • pV = constant
  • P1V1 = P2V2
  • Temperature remains constant.
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8
Q

What happens to the molecules when they expand due to heat and what is this process called?

A
  • Thermal expansion

- The molecules move/(vibrate if it’s a solid) faster so the gaps between the molecules increase.

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9
Q

When thermal expansion occurs.

Order the 3 states into the order of how much they expand. (Lowest to highest)

A
  • Solid
  • Liquid
  • Gas
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10
Q

Uses of thermal expansion? (2)

A
  • Thermometers

- Thermostats

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11
Q

What is a thermostat? Describe the experiment.

A

Take a bimetallic strip and hold it above a flame from a bunsen burner. The strip will bend away from the flame. This is because the molecules at the bottom of the bimetallic strip (that’s closest to the flame) expands.

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12
Q

Disadvantages of thermal expansion? (3)

A
  • Bridges (don’t want them to expand)
  • Power lines (can break)
  • Freezing pipes (can burst)
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13
Q
  • What are fixed points?

- Fixed points of water?

A
  • The freezing and boiling point of a substance

- 0 degree C and 100 degree C

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14
Q

Define sensitivity

A

The expansion (or change) per degree celcius

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15
Q

Define linearity

A

The same expansion (or change) per degree celcius

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16
Q

What does the range of a thermometer depend on?

A

The boiling point and freezing points of the liquid or other properties as well.

17
Q

What apparatus is used to measure temperature difference between 2 different metals?

A

Thermocouple

18
Q

Describe the wires of a thermocouple and give examples of each

A
  • There are 3 wires.
  • Wires 1 and 2 are made of the same material e.g. copper
  • Wire 3 is different to wires 1 and 2 e.g. constantan

You can’t have 2 wires made of very conductive metals or both that are made of very conductive metals.

You would have one of each.

19
Q

What must the junction have on a thermocouple?

A

2 different wires meeting at the junction

20
Q

How do the wires cause a voltage in a thermocouple?

Examples of meters that are used to measure the voltage produced. (4)

A

The two different wires joined together, at the same temperature will cause a voltage. This is read on a meter such as:

  • Galvanometer
  • Millivoltmeter
  • Milliammeter
  • Digital voltmeter or ammeter
21
Q

In a thermocouple what is commonly done with the cold junction?

A

It’s put into ice. This is so we can compare the temperature to a known valur (0 degree C)

22
Q

Advantages of a thermocouple? (6)

A
  • Rapid response to change in temperature
  • Small thermal capacity - doesn’t affect the measurement
  • Can be used as a data logger for continuous measurement
  • Can measure a large range
  • Has a small area
  • Can be used for remote readings if connected via the internet to a PC and the internet
23
Q

What is the internal energy?

A

The internal energy is the sum of all the KE and PE energies of its atoms/ molecules

24
Q

How do you increase the internal energy? (2)

A
  • Supply more thermal energy

- Doing work on the system e.g. compressing it

25
Q

Define heat capacity

A

Heat capacity is the amount of energy required to raise the temperature of a body by 1K or 1 degree C

26
Q

Define specific heat capacity

A

Specific heat capacity is the amount of energy required to raise 1Kg (unit mass) of a substance by 1K or 1 degree C

27
Q

Specific heat capacity = ?

Include units and symbols

A

specific heat capacity = energy supplied / (mass * delta feta(or temperature))

C = Q / (m*delta T)

Specific heat capacity = C (J/kg/degree C)
Energy supplied = Q (J)
Change in temperature = delta T(or feta) (degree C)

28
Q

1-What is latent heat of fusion?

2-What is latent heat of vaporisation?

A

1-Solid to a liquid vice-versa

2-Liquid to gas vice-versa

29
Q

Define specific latent heat

A

Specific latent heat is the energy needed per Kg of a substance to change the state

30
Q

Specific latent heat of fusion = ?

Include units and symbols

A

Specific latent heat of fusion = energy supplied / mass of substance melted

L = Q / M

L = specific latent heat (J/Kg)
Q = energy supplied (J)
M = mass (kg)

Remember to use the E = Pt or E = VIt if Q is not directly given to you.

If you use g for mass then change the unit for L to J/g

31
Q

Specific latent heat of vaporisation = ?

Include units and symbols

A

Specific latent heat of vaporisation = energy supplied / mass of substance vaporised

L = Q / M

L = specific latent heat of vaporisation (J/kg)
Q = energy supplied (J)
M = mass (kg)

Remember to use the E = Pt or E = VIt if Q is not directly given to you.

If you use g for mass then change the unit for L to J/g

32
Q

Rules for latent heat? (2)

A
  • Energy is supplied to melt or boil a substance

- Energy is given out on freezing or condensation

33
Q

4 methods of heat transfer and what they can happen in

A
  • Conduction = mainly solids
  • Convection = fluids
  • Radiation = doesn’t require a medium so it can happen in a vacuum
  • Evaporation
34
Q

Thermal radiation is the same as what?

A

Infrared radiation which is an EM wave

35
Q

1-What objects are better are absorbing and emitting radiation?

2-What objects are worse at absorbing and emitting radiation? Why?

A

1-Dull and dark objects

2-Shiny and light objects. Shiny objects reflect light.

36
Q

Ways to insulate a house? (5)

A
  • Double glazing
  • Cavity wall insulation
  • Loft insulation
  • Insulate hot water tank - so you don’t waste heat
  • Turn down the radiators

IGCSE Physics (6 decks)

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