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Physics > 11 Changes of State and SHC - 4th Form > Flashcards

11 Changes of State and SHC - 4th Form Flashcards

1
Q

If the specific heat capacity of water is 4200 J/kg°C, how much energy is needed to raise 1 kg of

water by 2°C?

A

8400 J

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2
Q

What is the unit for Energy?

A

Joules

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3
Q

The total energy which matter possesses is called its internal energy.

This is the total kinetic and potential energy of all the particles.

Which state of matter possesses the most energy?

A

gas

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4
Q

Which material has the lowest specific heat capacity? How do you know?

A

aluminium

It requires less energy for the same temperature change as water.

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5
Q

Which state of matter has a fixed volume but an indefinite shape?

A

liquid - it has a fixed volume but can take the shape of its container

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6
Q

Describe the particle movement in a solid

A
  • vibrating in fixed positions
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7
Q

What is the equation linking energy, mass, specific heat capactiy and change in temperature?

A
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8
Q

If the force of attraction between particles in a liquid is moderate, how does this change when in gaseous form?

A
  • the force of attraction between particles is very weak or negligible, the particles move freely and are far apart in a gas.
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9
Q

What safety precautions must be taken when finding the specific heat capacity of water?

A
  • heater and water will be hot- handle with care, let cool before clearing away
  • water and electricity may lead to an electric shock- do not operate equipment with wet hand, check insulation on wires is intact before using.
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10
Q

Sketch a typical heating curve for a substance.

A
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11
Q

Name the three states of matter

A

solid, liquid and gas

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12
Q

gas to solid

Name the change of state

A

deposition

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13
Q

If ice from a cold freezer is put in a warm room, it absorbs thermal energy.

The ice warms up and begins to melt.

How does the temperature vary with time while the ice warms from -4°C to 4°C?

A
  • as the ice warms up the temperature rises from -4°C to 0°C.
  • at 0°C the temperature of the ice remains constant while the ice melts.
  • when all the ice has melted the temperature begins rise again from 0°C to 4°C
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14
Q

How is kinetic energy of a substance related to its temperature?

A

Kinetic energy is proportional to the average kinetic energy of the particle in the substance

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15
Q

gas to liquid

Name the change of state

A

condensation

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16
Q

Describe the particle movement in a gas

A
  • moving fast and moving freely
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17
Q

How is the energy supplied to the water calculated when finding the specific heat capacity of water?

A

E = IVt

Energy = Current (A) x voltage (V) x time (s)

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18
Q

How do you improve accuracy when measuring the mass of a metal block using a balance?

A
  • tare balance before use
  • place balance on level surface
19
Q

Which state of matter possesses the most potential energy?

A

gas - particles are the furthest apart

20
Q

solid to liquid

Name the change of state

A

melting

21
Q

Which state of matter possesses the most kinetic energy?

A

gas - particles are moving the fastest

22
Q

If the specific heat capacity of water is 4200 J/kg°C, how much energy is needed to raise 2 kg of

water by 2°C?

A

4200 x 4 = 16 800 J

23
Q

How do you improve the reliability of your result when measuring the specific heat capacity of a metal block?

A

Repeat the experiment 3 times to see if similar results are obtained

24
Q

Which state of matter possesses the most kinetic energy?

A

gas - particles are moving the fastest

25
Q

If 1 kilogram of alcohol at 20°C lost 5000 J of energy, what would its final temperature be?

Specific heat capacity of alcohol = 2500J/kg°C

A

change in temperature = E / mc

= 5000J / (1 kg x 2500 J/kg°C)

= 2 °C

20 -2 = 18°C

26
Q

Explain the temperature change in the graph below.

A
  • Q-R the energy supplied increases the kinetic energy of the particles- temperature increases
  • R-S all the energy supplied goes into weakening intermolecular bonds to induce the state change- temperature stays constant
  • S-T - the state change is completed- energy supplied increases the kinetic energy of the particles- raising the temperature once again.
27
Q

Which material will cool more quickly?

A

aluminium

less energy needs to be removed for the same temperature drop.

28
Q

What equipment is needed to find the specific heat capacity of an aluminium block?

A
  • aluminium block, power supply, electric heater and thermometer
  • stopwatch
  • voltmeter
  • ammeter
  • lagging for top and side of block
  • mat for bottom of block
29
Q

Describe the particle arrangement in a gas

A
  • far apart - irregular arrangment
30
Q

Describe the particle arrangement in a solid

A
  • close together - regular arrangement
31
Q

Which state of matter has an indefinite volume and indefinite shape?

A

gas - it expand to fill the volume and shape of its container.

32
Q

Samuel used the equipment below to measure the specific heat capacity of water. His value was

5100 J/kg°C.

The true value is 4200J/kg°C.

Explain why his value is too big?

A
  • Not all the energy supplied by the heater goes to the water, some is lost to heating the heater and to the surroundings - Q [energy supplied] is too big

E=IVt

  • as a result the temperature change is too low

A bigger than expected Q divided by a smaller than expected change in T means the specific heat capacity will always be too big!

33
Q

Describe the particle movement in a liquid

A
  • vibrating and slipping past each other
34
Q

When an object is supplied with energy the internal energy of the object increases. This means the kinetic energy of the particles increases and we see -a change in temperature.

A certain points, the energy supplied to a substance is ‘hidden’ and no temperature change is seen. Here the energy which is supplied goes to breaking the intermolecular forces/bonds between the particles.

What is happening at this point?

A

The substance is going through a change of state.

35
Q

Which material has the highest specific heat capacity? How do you know?

A

water

It requires more energy for the same temperature change as aluminium.

36
Q

solid to gas

Name the change of state

A

sublimation

37
Q

Describe the particle arrangement in a liquid

A
  • close together - irregular arrangement
38
Q

liquid to solid

Name the change of state

A

freezing

39
Q

liquid to gas

Name the change of state

A

evaporation

40
Q

If the specific heat capacity of water is 4200 J/kg°C, how much energy is needed to raise 2 kg of

water by 1°C?

A

8400 J

41
Q

Define specific heat capacity

A

The energy required to heat 1 kg of a substance by 1°C

42
Q

If the force of attraction between particles in a solid is strong, how does this change when in liquid form?

A
  • the force of attraction between particles is moderate, the particles can now slip past each other
43
Q

Which state of matter has a fixed shape and a fixed volume?

A

solid

44
Q

Most central heating systems use water to carry thermal energy. Why is water a good choice in this application?

A

Water has a very high specific heat capacity.

It is very good a storing energy, carrying it from the boiler and releasing it at the radiators

Physics (28 decks)

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