Investigating the specific heat capacity

In a nutshell

By recording the temperature of materials as they change, the specific heat capacity of each material can be investigated. You will do this by conducting two experiments. One will look at the energy supplied to change the temperature of blocks of metals over a period of time and the other will look at the energy supplied to change the temperature of water over a period of time.

Equations

Word Equation	Symbol Equation
$change \space in \space thermal\space energy = mass \times specific \space heat\space capacity \times change \space in \space temperature$	$\Delta E = m\times c \times \Delta \theta$
$thermal \space energy = current \times potential \space difference \times time$	$E = I\times V \times t$

Note: $\Delta$ means 'change of' which is the difference between the final and initial value.

Variable definitions

Quantity Name	Symbol	unit name	Unit
$thermal \space energy$	$E$	$joule$	$J$
$mass$	$m$	$kilogram$	$kg$
$specific \space heat \space capacity$	$c$	$joule \space per \space kilgram \space per \space degree \space Celsius$	$J/kg \degree C$
$temperature$	$\theta$	$degree \space Celsius$	$\degree C$
$current$	$I$	$ampere$	$A$
$potential \space difference$	$V$	$volt$	$V$
$time$	$t$	$second$	$s$

Equipment list

The following equipment list can be used to conduct the experiment to investigate the specific heat capacity of different materials.

Equipment	Use
$1\,kg$ blocks of copper, iron and aluminium, with two holes in each	To find the specific heat capacity of.
Thermometer	To measure the temperature.
Pipette	To add a drop of water in the thermometer hole.
Insulation	To wrap around the materials to prevent heat loss.
$12\,V$ immersion heater	To heat the materials.
$12\,V$ power supply	To provide power to the immersion heater.
Stopwatch	To time the experiment.
Ammeter and Voltmeter	To find the power of the heater by measuring the potential difference and current through the heater.
Five connecting leads	To connect the power supply, ammeter, voltmeter and immersion heater.
Water	To find the specific heat capacity of.
$400\,ml$ beaker	To hold the water.

Note: If the mass of the blocks are unknown, also include a digital balance to find the mass.

Experimental variables

The independent variable is the variable you change. The dependent variable is the variable that changes depending on the other variables, and is the one you measure. The control variables are the variables that are kept constant.

Independent Variable	$Time$
Dependent Variable	$Temperature$
Control Variables	$Same\ material\ for\ each\ set\ of\ measurements,\ current\ supplied,\ potential\ difference\ supplied$

Safety precautions

When performing experiments, it is very important to consider safety precautions. This is so that no one gets hurt or injured during the experiment.

Hazard	Risk	Safety Measure
Heater	Touching the heater whilst it is on or just after it is switched off could result in burns.	Don't touch the heater whilst it is still hot. If burnt, run the burn under cold running water for five minutes.
Hot equipment	The equipment (heater, block, wire etc.) will remain hot for a while after it has been used.	Don't pack away immediately, wait until the equipment has cooled.
Water and electrics.	Water mixing with the electrical equipment could cause it to break or start a fire.	Keep the water away from all electrical equipment.

Method

These are the instructions to complete the experiment. Record all measurements taken as you work through the experiment in a table.

Physics; Physics practicals; KS4 Year 10; Investigating the specific heat capacity

1.	Thermometer
2.	Metal block
3.	Immersion heater
4.	Voltmeter
5.	Ammeter
6.	Power supply

1.	Set up the apparatus as shown in the diagram. Wrap the insulation around the base and sides of the block.
2.	Drop water inside the thermometer hole and place the thermometer in this hole.
3.	Measure the initial temperature of the block and start the timer.
4.	Switch the power supply on at $12\,V$ and record the ammeter and voltmeter readings. Note: The voltmeter and ammeter readings should not change during the experiment.
5.	Record the temperature measured by the thermometer every minute for 10 minutes.
6.	Repeat steps 1-5 for each other metal block.

Analysis

This is how you will use the data recorded to form conclusions.

1.	For each measurement of the temperature, calculate the work done by the heater. This is done by using the thermal energy equation $thermal \space energy = current \times potential \space difference \times time \newline \ \newline E= I\times V\times t$ Note: The power of the heater can be found using $P = I \times V$ . This is what the equation above is derived from.
2.	Plot a graph of the temperature of each metal block against the work done. Draw a line of best fit for each line for this graph.
3.	Calculate the gradient of all your lines of best fit. Tip: The beginning of your graph may be curved so ignore this part when finding each gradient of the line.
4.	Use the gradients of the graph to calculate the specific heat capacity of each block. As the mass is equal to $1 \,kg$ , this is done by using the formula $specific \space heat \space capacity,\: c = \dfrac{1}{gradient}$ Note: If the mass of the block you used was not equal to $1 \,kg$ , you will have to divide by the mass to find the specific heat capacity. You can check this by considering the units of the equation.

Conclusion

Physics; Physics practicals; KS4 Year 10; Investigating the specific heat capacity

A.	Temperature of the metal block ( $\degree C$ )
B.	Work done by the heater ( $J$ )

The horizontal and vertical lines are used for calculating the gradient.

The graph from the measured values of the experiment should look similar to this. The copper line should be the steepest as it has the lowest specific heat capacity. The aluminium line should be the least steep as it has the highest specific heat capacity. This means it takes less energy to change the temperature of aluminium than it does to change the temperature of copper by the same result.

Evaluation

Once you have completed your experiment, it is important to consider how it could be improved. You should come up with ways to improve the accuracy of your values. If you got a result that seems unreasonable, think about why this was.

Experiment 2: Investigating the specific heat capacity of water.

Experimental variables

The independent variable is the variable you change. The dependent variable is the variable that changes depending on the other variables, and is the one you measure. The control variables are the variables that are kept constant.

Independent Variable	$Time$
Dependent Variable	$Temperature$
Control Variables	$Water,\ current\ supplied,\ potential\ difference\ supplied$

Safety precautions

When performing experiments, it is very important to consider safety precautions. This is so that no one gets hurt or injured during the experiment.

Hazard	Risk	Safety Measure
Heater	Touching the heater whilst it is on or just after it is switched off could result in burns.	Don't touch the heater whilst it is still hot. If burnt, run the burn under cold running water for five minutes.
Hot equipment	The equipment (heater, wire etc.) will remain hot for a while after it has been used.	Don't pack away immediately, wait until the equipment has cooled.
Water and electrics.	Water mixing with the electrical equipment could cause it to break or start a fire.	Try your best to isolate the electrics from the water.

Method

These are the instructions to complete the experiment. Record all measurements taken as you work through the experiment in a table.

Physics; Physics practicals; KS4 Year 10; Investigating the specific heat capacity

1.	Thermometer
2.	Metal block
3.	Immersion heater
4.	Voltmeter
5.	Ammeter
6.	Power supply

1.	Place the beaker on the digital balance and reset the balance to zero. This makes sure the mass of the beaker isn't included in the mass of the water.
2.	Fill the beaker with $250\,ml$ of water and measure the mass.
3.	Set up the apparatus as shown in the diagram. Place the immersion heater and and thermometer in the water.
4.	Record the initial temperature of the water using the thermometer and start the timer.
5.	Switch the power supply on at $12\,V$ and record the ammeter and voltmeter readings. Note: The voltmeter and ammeter readings should not change during the experiment.
6.	Record the temperature measured by the thermometer every minute for $10$ minutes.

Analysis

This is how you will use the data recorded to form conclusions.

Follow the same procedure as the previous experiment. When calculating the specific heat capacity, you will have to divide the reciprocal of the gradient by the mass of the water.

$c = \dfrac{1}{gradient \times m_{water}}$

Conclusion

Physics; Physics practicals; KS4 Year 10; Investigating the specific heat capacity

A.	Temperature of the water ( $\degree C$ )
B.	Work done by the heater ( $J$ )
1.	Line of best fit

The graph from the measured values of the experiment should look similar to this. The specific heat capacity of water is $4200 \,J/kg\,\degree C$ to two significant figures. The calculation made from the gradient from your graph should be around this value.

Evaluation

This is the same as the previous experiment.