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RGS 4th Form Physics MAC > 6 Changes of State > Flashcards

6 Changes of State Flashcards

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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

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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4
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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5
Q

Describe the particle movement in a solid

A
  • vibrating in fixed positions
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6
Q

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

A
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7
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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8
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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9
Q

Sketch a typical heating curve for a substance.

A
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10
Q

Name the three states of matter

A

solid, liquid and gas

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11
Q

gas to solid

Name the change of state

A

deposition

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12
Q

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

A

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

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13
Q

gas to liquid

Name the change of state

A

condensation

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14
Q

Describe the particle movement in a gas

A
  • moving fast and moving freely
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15
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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16
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
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17
Q

Which state of matter possesses the most potential energy?

A

gas - particles are the furthest apart

18
Q

solid to liquid

Name the change of state

A

melting

19
Q

Which state of matter possesses the most kinetic energy?

A

gas - particles are moving the fastest

20
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

21
Q

What can be done to obtain a more accurate value for the specific heat capacity of a metal?

A
  • lagging, lid and insulating mat- reduces energy loss to surrounding.
  • Turn on heater and allow it to heat up before placing it in the block- reduces energy lost to heating up heater
  • turn off heater and stopwatch but continue to record temperature until peak temperature of block is reached
22
Q

Which state of matter possesses the most kinetic energy?

A

gas - particles are moving the fastest

23
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

24
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.
25
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
26
Q

Describe the particle arrangement in a gas

A
  • far apart - irregular arrangment
27
Q

Describe the particle arrangement in a solid

A
  • close together - regular arrangement
28
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.

29
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
30
Q

Describe how the temperature varies with time for the cooling curve below

A
  • For the first 4 minutes the temperature drops from 88°C to 80°C at a decreasing rate.
  • From 4 minutes to 11 minutes the temperature remains constant at 80°C
  • At 12 minutes the temperature decreases at an increasing rate.
31
Q

Describe the particle movement in a liquid

A
  • vibrating and slipping past each other
32
Q

solid to gas

Name the change of state

A

sublimation

33
Q

liquid to solid

Name the change of state

A

freezing

34
Q

liquid to gas

Name the change of state

A

evaporation

35
Q

Define specific heat capacity

A

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

36
Q

How does the specific heat capacity of water and sand help create the land breeze during nighttime?

A
  • Both sand and water are cooling
  • Water has a much higher specific heat capacity than sand and so the water cools more slowly than the sand.
  • The hotter water heats the air above it, this hot air expands and becomes less dense and rises
  • Cool air above the sand moves across to replace it
  • A convection current is set-up
37
Q

Calculate the specific heat capacity of the following object

  • mass of block= 1000 g
  • current = 2A
  • voltage = 12 V
  • time = 200 s
  • temperature change = 10°C
A

E = IVt = 2A x V x 200 s = 4800 J

c = 4800 J / (1 kg x 10°C)

c = 480 J/kg°C

38
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
39
Q

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

A

solid

40
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

RGS 4th Form Physics MAC (8 decks)

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