Specific Heat Capacity (Physics)Practical activity Apparatus and techniques

An investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

Use appropriate apparatus to make and record measurements of mass, time and temperature accurately.

Use, in a safe manner, appropriate apparatus to measure energy changes/transfers and associated values such as work done.

What is the specific heat capacity of copper?In this investigation you will heat up a block of copper using an electric heater.

You will measure:

mass

work done by the heater

temperature.

You will plot a graph of temperature against work done. The gradient of this graph and the mass of the block will be used to determine the specific heat capacity of copper.

Equipment copper block wrapped in

insulation, with two holes for a thermometer and heater

thermometer

pipette to put water in the thermometer hole

30 W heater

12 V power supply

insulation to wrap around the blocks

ammeter and voltmeter

five 4 mm leads

stop watch or stop clock

balance.

Method

Read these instructions carefully before you start work.

1. Measure and record the mass of the a metal block ………………………….kg

2. Place a heater in the larger hole in the block. (add water or oil to allow good thermal connection)

3. Connect the ammeter, power pack and heater in series.

4. Connect the voltmeter across the power pack.

5. Use the pipette to put a small amount of water in the other hole.

6. Put the thermometer in this hole.

7. Switch the power pack to 12 V. Switch it on. (NB: don’t touch the heater as it will now get very hot!)

8. Record the ammeter and voltmeter readings. These shouldn’t change during the experiment but you can take an average or mean to be sure. (see table later)

9. Measure the temperature and switch on the stop clock.

10.Record the temperature every minute for 10 minutes.

Add your results to a table… (+ see step 11)

Block Type: Aluminium / Copper / Brass / Steel

Time in secondsWork done in J

(E = VIt)Temperature in °C

0

60

120

180

240

300

360

420

480

540

600

11. Record V and I and mean then Calculate the power of the heater in watts. (Power = Voltage x Current OR P = VI). To do this, multiply the ammeter reading by the voltmeter reading.

1 2 3 Mean

Voltmeter /V

Ammeter /I

Power /W

12. Calculate the work done by the heater. To do this, multiply the time in seconds by the power of the heater. (P = E/t or P x t = E). Put an example here…

………………………………………………………………………………………………………

……………………………………………………………………………………………………..

Temperature in °C

Work done in J

13. Plot a graph of temperature in oC against work done in J.

14. Draw a line of best fit. Take care as the beginning of the graph may be curved.

15. Mark two points on the line you have drawn and calculate the change in temperature (T) and the change in work done (E) between these points

………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………

16. Calculate the specific heat capacity of the copper (c ) by using the equation….

c = Qm T were m is the mass of the copper block (1kg so simplfies)

………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………

17. Repeat this experiment for blocks made from other materials such as aluminium and iron. Write your findings in a similar way in your book by writing your own tables and graphs OR you may just quote some values for other blocks here….

Aluminium = Copper = Brass = Steel =

18. In your book review other methods for this experiment to extend your work…a. Draw a diagramb. Identify independent, dependant, control variablesc. Write out a short method for eachd. Possible results table

Specific Heat Capacity of an Unknown Block (Extension Practical)

You are going to calculate the specific heat capacities of two materials.

Safety information

Hold the hot density cube at arm’s length and away from other people when transferring from one beaker to another.

Apparatus

beakers

density cubes, each tied to a clamp stand or cotton(for example, brass, aluminium)

water

tripod, gauze, mat Bunsen burner (blue flame)

OR waterbath at 80C

thermometer

balance (mass)

Diagram

Method

1. Set up the apparatus as shown in the diagram.

2. Measure and record the mass of the density cube.

3. Put an empty 250 ml beaker on the balance and zero the reading. Pour as close to 150 ml into the beaker as possible. Record the mass of the water. Record the temperature and keep it to one side. Do not heat this beaker.

4. Heat about half a beaker of water (in the other beaker) until it is boiling. OR use a hot water bath (approx 80C)

5. Reduce the flame to allow the water to simmer.

6. Submerge the density cube in the boiling water for around 30 s until the cube is the same temperature as the water. (tie to a piece of cotton before this)

7. Transfer the density cube carefully and swiftly to the beaker that you put to one side earlier.

8. Add the cardboard lid and stir while reading the temperature and record the maximum temperature of the water (the cube will now be at this temperature too).

Analyse and interpret data

1. What is the boiling point of water (and therefore of the density cube)?

2. What was the final temperature of the water with the cube cooled in it?

Hint: The final temperature of the water is also the final temperature of the density cube.

Once you have calculated the two energies using the table to help, use the equation below to help you calculate the specific heat capacity for the cube’s material (for example, brass). And add it to the table.

You will need to rearrange your equation for the unknown value of the specific heat capacity of the cube’s material.

Energy ‘lost’ of heated metal cube = Energy ‘gained’ warmed water

3. If the actual value for the specific heat capacity of ……………….. is ……………. J/(kg °C), what is the percentage difference for your value? (Harder)

Cube: Water (2nd beaker)

Mass of ………………. density cube mb (kg)

Mass of water, mw (kg)

Starting temperature of cube (°C) (in hot water)

Starting temperature of cold water (°C)

Final temperature of cube (°C) (in colder water)

Final temperature of water (°C) (when block added)

Temperature change ∆Tb (°C)

Temperature difference ∆Tw

(°C)

Specific heat capacity of cube material, cb (J/(kg °C))

E /( mb x Tb)

xSpecific heat capacity of water, cw (J/(kg °C))

4200

Q Energy ‘lost’ of heated cube:

mb × cb x Tb (J)

Q Energy ‘gained’ of warmed water

mw × cw × Tw (J)

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1.  

Time: 28 minutes

Score: /28 marks

WWW:

EBI:

Low Challenge Q1.The electric kettle shown below is used to boil water.

(a)     After the water has boiled, the temperature of the water decreases by 22 °C.

The mass of water in the kettle is 0.50 kg.The specific heat capacity of water is 4200 J/kg °C.

Calculate the energy transferred to the surroundings from the water.

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

Energy = ....................... joules(2)

(b)     Why is the total energy input to the kettle higher than the energy used to heat the water?

Tick (✔) one box. 

    Tick (✔)

  Energy is absorbed from the surroundings.  

  Energy is used to heat the kettle.  

  The kettle is more than 100% efficient.  

(1)(Total 3 marks)

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Medium Challenge Q2.A new design for a kettle is made from two layers of plastic separated by a vacuum.

After the water in the kettle has boiled, the water stays hot for at least 2 hours.

The new kettle is shown below.

 

(a)     The energy transferred from the water in the kettle to the surroundings in 2 hours is 46 200 J.

The mass of water in the kettle is 0.50 kg.

The specific heat capacity of water is 4200 J/kg °C.

The initial temperature of the water is 100 °C.

Calculate the temperature of the water in the kettle after 2 hours.

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

Temperature after 2 hours = ...................... °C (3)

(b)     Calculate the average power output from the water in the kettle to the surroundings in 2 hours.

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

.............................................................................................................................

Average power output = ........................... W (2)(Total 5 marks)

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Q3.The diagram shows how one type of electric storage heater is constructed. The heater has ceramic bricks inside. The electric elements heat the ceramic bricks during the night. Later, during the daytime, the ceramic bricks transfer the stored energy to the room.

(a)     (i)      Complete the following sentences using words from the box. 

  conduction convection evaporation

Energy is transferred through the metal casing by .....................................

The warm air rising from the heater transfers energy to the

room by ................................................(2)

(ii)     The inside of the metal case is insulated.

Which one of the following gives the reason why?

Tick ( ) one box. 

  To transfer energy from the ceramic bricks to the room faster

  To stop energy from the room transferring into the heater

  To keep the ceramic bricks hot for a longer time

(1)

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(b)     In winter, the electricity supply to a 2.6 kW storage heater is switched on for seven hours each day.

(i)      Calculate the energy transferred, in kilowatt-hours, from the electricity supply to the heater in seven hours.

Show clearly how you work out your answer.

...............................................................................................................

...............................................................................................................

Energy transferred = .................................................. kWh(2)

(ii)     The electricity supply to the heater is always switched on between midnight and 7 am. Between these hours, electricity costs 5 p per kilowatt-hour.

Calculate how much it costs to have the heater switched on between midnight and 7 am.

...............................................................................................................

...............................................................................................................

Cost = .................................................. p(1)

(c)     Between 7 am and 8 am, after the electricity supply is switched off, the temperature of the ceramic bricks falls by 25 °C.

Calculate the energy transferred from the ceramic bricks between 7 am and 8 am.

Total mass of ceramic bricks = 120 kg.Specific heat capacity of the ceramic bricks = 750 J/kg °C.

Show clearly how you work out your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

                                Energy transferred = .................................................. J(2)

(Total 8 marks)

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Q4.Heat exchangers are devices used to transfer heat from one place to another.

The diagram shows a pipe being used as a simple heat exchanger by a student in an investigation.

Heat is transferred from the hot water inside the pipe to the cold water outside the pipe.

 

(a)     Complete the following sentence by drawing a ring around the correct word in the box.

Heat is transferred from the hot water inside the pipe 

    conduction.

  to the cold water outside the pipe by convection.

    radiation.

(1)

(b)     The student wanted to find out if the efficiency of a heat exchanger depends on the material used to make the pipe. The student tested three different materials. For each material, the rate of flow of hot water through the pipe was kept the same.

The student’s results are recorded in the table. 

  Material Temperature of the cold water at the start in °C

Temperature of the cold water after 10 minutes in °C

  Copper 20 36

  Glass 20 23

  Plastic 20 21

(i)      The rate of flow of hot water through the pipe was one of the control variables in

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the investigation.

Give one other control variable in the investigation.

...............................................................................................................(1)

(ii)     Which one of the three materials made the best heat exchanger?

...............................................................................................................

Give a reason for your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(c)     The student finds a picture of a heat exchanger used in an industrial laundry.The heat exchanger uses hot, dirty water to heat cold, clean water.

 

This heat exchanger transfers heat faster than the heat exchanger the student used in the investigation.

Explain why.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 6 marks)

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Higher Challenge Q5.A student used the apparatus in Figure 1 to obtain the data needed to calculate the

specific heat capacity of copper.

Figure 1

The initial temperature of the copper block was measured.

The power supply was switched on.

The energy transferred by the heater to the block was measured using the joulemeter.

The temperature of the block was recorded every minute. The temperature increase was calculated.

Figure 2 shows the student’s results. Energy transferred to copper block in joules

(a)     Energy is transferred through the copper block.

What is the name of the process by which the energy is transferred?

  Conduction

  Convection

  Radiation

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(b)     Use Figure 2 to determine how much energy was needed to increase the temperature of the copper block by 35 °C.

.................................. joules (1)

(c)     The copper block has a mass of 2 kg

Use your answer to part (b) to calculate the value given by this experiment for the specific heat capacity of copper. Give the unit.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Specific heat capacity = ............................................................(3)

(d)     This experiment does not give the correct value for the specific heat of copper.

Suggest one reason why.

........................................................................................................................

........................................................................................................................(1)

(Total 6 marks)

Versions of the ExperimentRemember in the exam you will be asked to think about a different method and apply your learning. Here are some more examples to get you started…

Both these experiments rely on a change of temperature either by mixing liquids or a liquid and solid at different temperatures. One warms and one cools to become a new temperature. It requires a simultaneous equation to solve. (Challenge Maths)

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You may be asked for an experiment using water

You may be asked for an experiment using an insulated “calorimeter” and asked to discuss convection, conduction and radiation in detail.

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Specific VocabularyThink about these words shown below, how do they relate to your practical? Write some ideas in the boxes below and discuss with a partner and your class?

Key Term Idea Applied to my Experiment?

Accuracy

A measurement result is considered accurate if it is judged to be close to the true value.

Precision

Precise measurements are ones in which there is very little spread about the mean value. Precision depends only on the extent of random errors – it gives no indication of how close results are to the true value.

Reproducible

A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained. Previously known as reliable.

True ValueThis is the value that would be obtained in an ideal measurement.

Dependent

Categoric, Continuous, Control, Independent, DependantIndependent

Variable Types

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1 SHC Mark Schemes…

M1.(a) 46 200accept 46 000allow 1 mark for correct substitutionie 0.5 × 4200 × 22 provided no subsequent step 2

(b)     Energy is used to heat the kettle. 1 [3]

M2.(a)     78 (°C)allow 2 marks for correct temperature change ie 22 °Callow 1 mark for correct substitutionie 46 200 = 0.5 × 4200 x θ or

3

(b)     6.4 (W)allow 2 marks for an answer that rounds to 6.4allow 1 mark for correct substitution ie 46 200 = P ×

7200 an answer of 23 000 or 23 100 or 385 gains 1 mark 2 [5]

M3.         (a)      (i)     conduction 1

convection 1correct order only

(ii)     to keep the ceramic bricks hot for a longer time 1

(b)    (i)       E = P × t

18.2allow 1 mark for correct substitution ie 2.6 × 7 provided

that no subsequent step is shown 2

(ii)     91 (p)or their (b)(i) × 5 correctly calculated

accept £0.91do not accept 0.91 without £ sign 1

(c)     E = m × c × θ

2 250 000allow 1 mark for correct substitution ie 120 × 750 × 25

provided that no subsequent step is shownanswers 2250 kJ or 2.25 MJ gain both marks 2 [8]

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M4.(a)    conduction 1

(b)     (i) any one from:

•        starting temperature (of cold water)temperature is insufficient

•        pipe length accept size of pipe

•        pipe diameter / pipe (wall) thickness / volume of cold wateraccept amount for volume

•        temperature of hot water (in) / time 1

(ii)     copper 1

greatest temperature changeonly scores if copper chosenaccept heat for temperatureaccept heated water the fastestaccept it was hottest (after 10 minutes)accept it is the best / a good conductor 1

(c)     the pipe has a larger (surface) area / accept pipe is longer 1

(so) hot / dirty water (inside pipe) is in contact with cold / clean water (outside pipe) for longer 1 [6]

M5.(a)     conduction 1

(b)     35 000 1

(c)     500their (b) = 2 x c x 35 correctly calculated scores 2 marksallow 1 mark for correct substitution ie 35000 = 2 x c x 35

or their (b) = 2 x c x 35 2J / kg°C 1

(d)     energy lost to surroundingsorenergy needed to warm heater

accept there is no insulation (on the copper block)

do not accept answers in terms of human error or poor results or defective equipment 1 [6]

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V

A

12V

1 Specific Heat Capacity - Lesson InformationRequired practical activity Apparatus and techniques

An investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

AT 1 - use appropriate apparatus to make and record measurements of mass, time and temperature accurately.

AT 5 – use, in a safe manner, appropriate apparatus to measure energy changes/transfers and associated values such as work done.

What is the specific heat capacity of copper?

MaterialsIn addition to access to general laboratory equipment, each group needs:

1 kg copper block with two holes – one for the heater and one for the thermometer

1 kg iron, aluminium or lead blocks for comparison

thermometer

pipette to put water in the thermometer hole

30 W heater

12 V power supply

insulation to wrap around the blocks

ammeter and voltmeter

4mm leads

stop watch or stop clock

balance (capable of measuring more than 1 kg) to determine the mass of the blocks

heatproof mat.

Technical informationThe method involves using the electric heaters to raise the temperature of the blocks. You may have blocks made for this experiment. The blocks usually have a mass of 1 kg and have holes that fit the heater and the thermometer. The heaters fit snugly but there is usually an air gap around the thermometer. A drop of water provides a better thermal contact. The blocks should be insulated to reduce heat loss to the surroundings.

The students will switch on the power supply and measure the current and potential difference. This is to obtain the power of the heater (power = IV) which should remain constant. Typically the heaters are either about 30 W or 50 W. The students can be told the power of the heater rather than measure

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it if preferred. The students measure and record the temperature of the block every minute for about 10 minutes. They then plot a graph of temperature against electrical work done by the heater. There is some thermal inertia as the block warms up so the beginning of the student’s graphs will not be linear if they start timing from when they switch on.

The student work sheet suggests comparing the specific heat capacities of three metals – aluminium, copper and iron. If you don’t have all three types of block, the experiment can become a simple measurement of one of them.

Additional informationThe specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

The students obtain values for current and potential difference (to work out the power), time and temperature. From the power and time they can work out the energy used, or electrical work done by the heater. A graph of temperature against electrical work done should be a straight line once the block has warmed a bit. Students use the gradient of this line and the mass of the block to work out the specific heat capacity. Having blocks of different materials allows students to see that specific heat capacities vary significantly, even between metals.

Metal Copper Aluminium Iron Lead

Specific heat capacity (J kg-1 K-1)

385 913 500 126

Using a 30 W heater for 10 minutes transfers 30 × 60 × 10 = 18 000 J

This would be sufficient to raise the temperature of 1 kg of copper from room temperature to about 70 °C, aluminium to about 40 °C and iron to 55 °C. This supports the idea that 10 minutes is an adequate length of time for the experiment.

An alternative method involves calculating the specific heat capacity of lead shot in a sealed tube. If the tube is turned, the lead shot will fall generating heat when it hits the bottom. If this is repeated 40 times, the work done can be calculated and the temperature rise of the shot can be used to calculate the specific heat capacity.

Risk assessment Risk assessment and risk management are the responsibility of the centre.

The mains leads of the power supplies should be checked. The heater connections should also be checked. They will also get hot, particularly if left on without being in contact with the blocks.

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E1.(a)     Three quarters of students answered correctly scoring 2 marks. Common mistakes included selecting the wrong equation

(b)     Over half the students scored this mark, with incorrect answers being split fairly evenly between the two other choices.

E2.(a)     This question discriminated well, a third of students scored all 3 marks. A third of students scored 2 marks for calculating the temperature change of 22°C. Surprisingly, many students thought the final temperature would be 122°C having added the 22°C to the initial temperature. These students still scored 2 marks for their calculation of temperature change provided working was shown. A surprising number of students failed to correctly subtract 22 from 100, believing the answer to be 88°C.

A number of students selected an incorrect equation. Some students scored 1 mark for the substitution only and then incorrectly rearranged to achieve an incorrect final answer. Students should be reminded that the substitution gains 1 mark, not the subsequent rearrangement.

(b)     Only one tenth of students scored 2 marks for the answer of 6.4 (W). Half the students scored 1 mark, with the most commonly seen answer of 23 100, which was achieved by dividing 46 200 by 2 (hours). A number of students attempted the conversion, but only got as far as minutes and ended with an answer of 385, which also scored 1 mark.

E3.          (a)     (i)     This was generally well-answered, although the most common mistake was to have conduction and convection the wrong way round.

(ii)     Most students chose the correct answer.

(b)     (i)      Students coped well with this calculation, the majority obtaining the correct answer of 18.2 kWh.

(ii)     This calculation however was very poorly answered. A very common answer was to write 7 x 5 = 35.

(c)     The majority of Students obtained the correct answer to this calculation, although some students were unable to show the correct number of zeroes.

 

 

E4.(a)     Only a minority of students gained the mark here. Most thought that heat was transferred through the pipe by convection.

(b)     (i)      Many students were able to correctly identify one other control variable – 'starting temperature' being the favourite.

(ii)      Most chose 'copper' as the material to make the best heat exchanger, but fewer managed a suitable explanation for their choice. Simply quoting figures from the data, 'copper reached 36°C', is not enough for

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any credit.

(c)     It was apparent that many students did not understand what was happening inside the industrial heat exchanger. There were more blank responses in this question than any other on the paper. Some thought that the coil was a heating element whilst others thought that it moved or spun round. 'It's industrial so it's better' was a common answer. Many thought that the purpose of the coil was to make the water flow faster. Few answers gained both marks.

E5.(a)     A very small amount of students did not identify conduction as the process by which energy is transferred through copper.

(b)     The majority of students answered correctly, of those who did not score the mark, the most common error was misreading the number on the x-axis (for a temperature increase of 35°C) as 30,500 instead of 35,000.

(c)     Around half of students scored two of the three marks available. This was usually for performing the calculation correctly, but failing to give the correct unit.

(d)     A very low proportion of students did not attempt this question, with less than a fifth scoring the mark. The most common incorrect answers referred to faulty apparatus, incorrect measurements or values not as stated in the question, e.g. the block was not 2kg.

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