Newton’s law of cooling

A/L Physics · G.C.E. Advanced Level · Grades 12–13

Aim

To verify Newton’s law of cooling.

Apparatus

• A calorimeter of hot water (85 °C)
• Thermometer and stopwatch
• Room temperature θ₀ = 25 °C

Method

1. Read the water temperature every 2 minutes.
2. Calculate θ − θ₀.
3. Calculate ln(θ − θ₀).
4. Plot ln(θ − θ₀) against t: gradient = −k.

Conclusion

ln(θ − θ₀) against t is a straight line, so the rate of cooling is proportional to (θ − θ₀): θ − θ₀ = (θ₁ − θ₀)e^(−kt).