How fast does a cup of tea cool?: a maths EPQ idea
A title to start from
How accurately does Newton's law of cooling predict how fast a cup of tea cools?
Why it works as an EPQ
A cheap, safe experiment produces your own data to test a model that is on the A Level course.
Scope and difficulty
Accessible. Accessible. Add a better model (for example with evaporation) only if time allows.
The maths
Builds on these A Level topics: Exponentials and logarithms · Differentiation · Integration.
You would learn:
- Solving first-order differential equations
- Fitting by linearising with logarithms
- Residual analysis
One possible plan
- Derive the exponential model from the differential equation.
- Record temperature every minute in different cups, with and without a lid.
- Estimate the constant by plotting ln(T − room temperature) against time.
- Evaluate where the model fails and why.
Pitfalls
- Hot liquids: follow your school's safety advice.
- Changing more than one thing between runs.
Where to start reading
- Search for: Newton's law of cooling experiment evaporation
- Search for: linearising exponential data logarithms
Making something? Read the artefact guide first: an artefact still needs a research-based written report.
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