Internal Energy & Energy Transfers Practice Questions

Question 1

4 marks

A vacuum flask contains $0.40\,\text{kg}$ of hot soup.

(a)

Define internal energy.

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(b)

The soup is poured into a pan and reheated on a hob.

State two factors, other than the energy transferred to the soup, that affect how much the temperature of the soup increases.

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Question 2

4 marks

(a)

Define the specific heat capacity of a substance.

/ 1

(b)

Which is the correct unit of specific heat capacity?

Tick (✓) one box.

$\text{J/kg}$
$\text{J/}^\circ\text{C}$
$\text{J/kg}\,^\circ\text{C}$
$\text{W/kg}$

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(c)

A kettle heats $2.0\,\text{kg}$ of water from $15\,^\circ\text{C}$ to $45\,^\circ\text{C}$ .

specific heat capacity of water $= 4200\,\text{J/kg}\,^\circ\text{C}$

Calculate the energy transferred to the water.

Use the Physics Equation Sheet.

Energy = .................... J

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Question 3

4 marks

A student heated a sample of candle wax until it was completely liquid. The liquid wax was then allowed to cool. The student recorded the temperature of the wax every minute.

The results are shown in the table.

Time in minutes	0	1	2	3	4	5	6	7	8	9
Temperature in $^\circ\text{C}$	92	78	70	64	64	64	64	58	50	44

(a)

Determine the melting point of the candle wax.

Melting point = .................... $^\circ\text{C}$

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(b)

State the state of the wax at $9$ minutes.

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(c)

Explain why the temperature of the wax did not change between $3$ minutes and $6$ minutes.

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Question 0

5 marks

A student heats a $0.50\,\text{kg}$ block of metal using an electric heater. The energy transferred to the block is $9000\,\text{J}$ and the temperature of the block rises by $40\,^\circ\text{C}$ .

(a)

Calculate the specific heat capacity of the metal.

Give the unit.

Use the Physics Equation Sheet.

Specific heat capacity = .................... Unit ....................

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(b)

The table shows the specific heat capacity of four metals.

Metal	Specific heat capacity in $\text{J/kg}\,^\circ\text{C}$
aluminium	900
iron	450
copper	385
lead	130

Use the table and your answer to part a to identify the metal the block is made from.

/ 1

Question 0

5 marks

In a foundry, solid aluminium is heated in a furnace until it melts.

specific latent heat of fusion of aluminium $= 3.9 \times 10^{5}\,\text{J/kg}$

(a)

Calculate the energy needed to melt $2.5\,\text{kg}$ of aluminium that is already at its melting point.

Use the Physics Equation Sheet.

Energy = .................... J

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(b)

Energy is still being transferred to the aluminium while it melts, but its temperature does not change.

Explain why.

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(c)

State the difference between the specific latent heat of fusion and the specific latent heat of vaporisation.

/ 1

Question 0

6 marks

A student measured the specific latent heat of fusion of water.

This is the method used.

Pack crushed ice at $0\,^\circ\text{C}$ into a filter funnel.
Place a $50\,\text{W}$ immersion heater in the middle of the ice.
Switch the heater on for $300$ seconds and collect the melted water in a beaker on a balance.
Record the mass of water collected.

The mass of water collected was $0.045\,\text{kg}$ .

(a)

Calculate the energy transferred by the immersion heater in $300$ seconds.

Energy = .................... J

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(b)

Calculate the specific latent heat of fusion of water given by the student's data.

Give your answer to 2 significant figures and give the unit.

Use the Physics Equation Sheet.

Specific latent heat of fusion = .................... Unit ....................

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(c)

Suggest why crushed ice is used rather than one large block of ice.

/ 1

Question 0

5 marks

(a)

Explain the difference between the specific heat capacity of a substance and the specific latent heat of a substance.

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(b)

Ethanol boils at $78\,^\circ\text{C}$ .

A beaker of ethanol is heated at a constant rate. Explain, in terms of the particles, what happens to the internal energy of the ethanol while it is boiling at $78\,^\circ\text{C}$ .

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Question 0

5 marks

A pure substance is taken from a freezer and heated at a constant rate. The graph shows how the temperature of the substance changed with time.

(a)

Use the graph to determine the melting point and the boiling point of the substance.

Melting point = .................... $^\circ\text{C}$

Boiling point = .................... $^\circ\text{C}$

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(b)

State the state of the substance after $6$ minutes of heating.

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(c)

The specific heat capacity of the solid is less than the specific heat capacity of the liquid.

Explain how the graph shows this.

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Question 0

4 marks

An electric storage heater contains a block of ceramic bricks. Overnight, electricity is used to heat the bricks so that their temperature rises by $200\,^\circ\text{C}$ .

The energy transferred to the bricks is $5.04 \times 10^{6}\,\text{J}$ .

specific heat capacity of the ceramic $= 840\,\text{J/kg}\,^\circ\text{C}$

(a)

Calculate the mass of the ceramic bricks in the heater.

Use the Physics Equation Sheet.

Mass = .................... kg

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(b)

State one assumption you have made in your calculation in part a.

/ 1

Question 0

7 marks

A student used a $60\,\text{W}$ immersion heater to heat $0.40\,\text{kg}$ of cooking oil in an insulated container.

The temperature of the oil rose from $18\,^\circ\text{C}$ to $48\,^\circ\text{C}$ in $5.0$ minutes.

(a)

Calculate the energy transferred by the immersion heater in $5.0$ minutes.

Energy = .................... J

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(b)

Calculate the specific heat capacity of the cooking oil given by the student's data.

Use the Physics Equation Sheet.

Specific heat capacity = .................... $\text{J/kg}\,^\circ\text{C}$

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(c)

The true value of the specific heat capacity of the cooking oil is lower than the value calculated in part b.

Explain why the student's method gives a value that is too high.

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Question 0

8 marks

A student investigated the specific latent heat of fusion of water using the apparatus shown.

Two identical funnels were each packed with crushed ice at $0\,^\circ\text{C}$ . A $45\,\text{W}$ immersion heater in funnel A was switched on for $400$ seconds. Funnel B had no heater. The water from each funnel was collected in a beaker.

Funnel	Mass of water collected in kg
A	0.062
B	0.008

(a)

Explain why the student set up funnel B.

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(b)

Calculate the specific latent heat of fusion of water given by the student's results.

Give your answer to 2 significant figures and give the unit.

Use the Physics Equation Sheet.

Specific latent heat of fusion = .................... Unit ....................

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(c)

Suggest one change to the apparatus that would reduce the mass of ice melted in funnel B.

/ 1

Question 0

7 marks

A tray holding $0.20\,\text{kg}$ of water at $18\,^\circ\text{C}$ is placed in a freezer. The water cools to $0\,^\circ\text{C}$ and then freezes completely.

specific heat capacity of water $= 4200\,\text{J/kg}\,^\circ\text{C}$

specific latent heat of fusion of water $= 3.34 \times 10^{5}\,\text{J/kg}$

The mass of the tray can be ignored.

(a)

Calculate the energy that must be transferred from the water to cool it from $18\,^\circ\text{C}$ to $0\,^\circ\text{C}$ .

Use the Physics Equation Sheet.

Energy = .................... J

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(b)

Calculate the energy that must then be transferred from the water at $0\,^\circ\text{C}$ to freeze it completely.

Energy = .................... J

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(c)

The freezer removes energy from the water at a constant rate of $40\,\text{W}$ .

Calculate the time taken for the water at $18\,^\circ\text{C}$ to freeze completely.

Time = .................... s

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Electricity

Particle Model of Matter

Atomic Structure

Forces

Waves

Magnetism & Electromagnetism

Space Physics

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