Physics 11–12 · Year 11
Specific heat capacity by electrical heating: water and an aluminium cylinder
Module 3: Waves and Thermodynamics (Thermodynamics)
School laboratory, not for home
In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.
The idea
A measured electrical energy input raises the temperature of a known mass by an amount fixed by the material's specific heat capacity.
Safety card
Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.
Hazards
- hot cylinder and heater element
- hot water
- heater run dry
Controls
- never switch on the heater outside the sample
- let the cylinder cool before handling
- safety glasses
Note
Heat and hot liquids: record the activity in RiskAssess (https://www.riskassess.com.au/) and follow the Science ASSIST risk management information sheet (https://asta.edu.au/resource/ais-risk-management-and-risk-assessment/).
What you need
- 12 V immersion heater (about 50 W), low-voltage supply, ammeter and voltmeter or a joulemeter
- 1.00 kg aluminium calorimetry cylinder with heater and thermometer holes, and a polystyrene cup with 0.200 kg of water
- Thermometer or temperature probe reading to 0.1 degree, stopwatch, electronic balance, insulation
How to do it
- Weigh the water (or use the 1.00 kg cylinder); record the starting temperature.
- Switch on the heater and record V and I; time 300 s while stirring the water gently.
- Record the highest temperature reached shortly after switching off.
- Compute energy E = V I t and specific heat c = E / (m delta T).
- Repeat once, then compare with the accepted values and account for losses.
What you should see
50 W for 300 s delivers 15 000 J. The 1.00 kg aluminium cylinder rises about 16.7 degrees (c = 900 J/(kg K)); 0.200 kg of water rises about 17.9 degrees (c = 4186 J/(kg K)). Measured values of c come out high because some of the energy heats the heater, the thermometer and the surroundings rather than the sample.
What changes
- What you change
- electrical energy supplied (heating time)
- What you measure
- temperature rise
- What you keep the same
- mass of the sample
- heater power
- insulation
Common misconceptions
Each of these ideas is wrong, and the activity is a chance to test it.
- Temperature and heat are the same thing; heat is energy transferred, temperature is a measure of particle kinetic energy.
- Metals heat up faster because they hold more heat; they need less energy per degree, so they hold less.
Curriculum references
The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.
Sources
The pages the author read to write this activity.