Interactive practical

Properties of water

Heat a weighed amount of water with an immersion heater and joulemeter to find its specific heat capacity, then plot a temperature–time graph for melting ice.

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GCSE Physics

Investigating the properties of water

Pearson Edexcel 1SC0 — matched to your course.

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Practical focus

Determine the specific heat capacity of water and record a temperature–time graph while crushed ice melts.

Practical method

Aim

Determine the specific heat capacity of water, and record how the temperature of crushed ice changes as it melts.

Variables

Independent variable: energy supplied (specific heat capacity) or time (melting)
Dependent variable: temperature of the water or ice
Control variables: mass of water or ice; heater power; insulation and stirring.

Apparatus

Insulated beaker
Immersion heater and joulemeter (or ammeter, voltmeter and stopwatch)
Balance
Thermometer or temperature probe
Stirrer
Crushed ice

Method

Specific heat capacity: measure 0.500 kg of water into an insulated beaker. Record the start temperature.
Heat with the immersion heater, stirring gently, until the temperature has risen by about 15 °C. Read the energy supplied from the joulemeter.
Calculate c = \(\dfrac{E}{m\Delta \theta }\).
Melting: place crushed ice from a freezer in a beaker with a thermometer and warm it gently in a water bath, stirring.
Record the temperature every 30 s until the ice has melted and the water has warmed to about 10 °C.
Plot temperature against time and identify the flat section.

Sample results

Crushed ice warmed gently in a water bath.

Time / min	0	1	2	3	4	5	6	7	8
Temperature / °C	−10.0	−4.0	0.0	0.0	0.0	0.0	0.0	3.0	8.0

Analysis

The temperature stays at 0 °C between 2 and 6 minutes while the ice melts: energy is still being transferred, but it changes the arrangement and potential energy of the particles rather than their average kinetic energy. For the specific heat capacity, a joulemeter reading of 33 600 J for 0.500 kg of water warmed by 15.0 °C gives c = 33 600 ÷ (0.500 × 15.0) = 4480 J/kg °C, above the accepted 4200 J/kg °C because some energy heated the beaker and the air.

Errors and improvements

Problem	Effect	Improvement
Energy heats the beaker and air	c too large	Insulate and fit a lid
Water not stirred	Uneven temperature	Stir gently before each reading
Heater not fully submerged	Energy transferred to the air	Make sure the heater element is covered

Risk assessment

Hazard	Risk	Control measure
Hot water and heater	Scalds and burns	Do not touch the heater; switch off before removing it
Electrical equipment and water	Electric shock	Use a low-voltage heater and dry hands

Common mistakes

Saying no energy is transferred during melting.
Using the final temperature instead of the rise.
Forgetting that the mass must be in kg.

Worked analysis

0.500 kg of water receives 33 600 J and warms from 18.0 °C to 33.0 °C. c = 33 600 ÷ (0.500 × 15.0) = 4480 J/kg °C.

Common misconception

During melting the temperature is constant, but energy is still being transferred to the substance.

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