Science · Middle school

Same heat, different temperature

Heat different masses with the same amount of heat: the joules are equal, the thermometer readings are not.

In the learning section below the figure, predict, try, complete the tasks and check yourself with short questions.

Fig. 1Same heat, different temperature

Change the masses, heat: the joules match, the degrees don’t

36.0 kJ → A 54.4 °C · B 28.6 °C

Beaker A: Water0.25 kg

Beaker B: Water1.00 kg

Time elapsed60 / 120 s

Heat given

Same heat in both beakers

36.0 kJ

Temperature rise

+34.4 °C

+8.6 °C

Given the same heat, Beaker A warmed 4 times as much.

Beaker A · Water: 54.4 °C; m × c × ΔT = 36.0 kJ
Beaker B · Water: 28.6 °C; m × c × ΔT = 36.0 kJ

Heat is energy transferred (J); temperature measures the average motion of the particles (°C). The same heat is shared among few particles in a little liquid and among many in a lot; a liquid with a smaller specific heat warms more for the same heat.

Your own values

Type a number; a decimal comma works too. Mass and liquid are set per beaker; power, starting temperature and time are shared.

Beaker A

Liquid

Mass

Beaker B

Liquid

Mass

Burner power

Starting temperature

Heating time

Learn

Progress is kept on this page only; no points are given.

1Predict
2Try
3Explain

Both burners run at the same power for the same time. Beaker A holds 0.25 kg of water, beaker B 1 kg. When the time is up, which has warmed more?

The numbers come from one model: Q = P · t and ΔT = Q / (m · c). Specific heats (J / (kg · °C)): water 4186, olive oil ≈ 1970, ethanol ≈ 2440. The temperature stops at the liquid’s limit: water boils at 100 °C and ethanol at 78 °C, after which the heat goes into evaporation (latent heat: water 2257 kJ/kg, ethanol 846 kJ/kg); olive oil smokes at ≈ 190 °C and the model stops there. Heating of the beaker and heat lost to the room are ignored; in reality the liquid warms a little less. Bubbles and steam are only a display.