Thermal equilibrium – dropping a hot object into water
PhysicsThermal Physics & GasesAges 17–18Virtual lab
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Thermal Physics & Gases
Object 1 (metal, water, or ice at 0 °C) with mass m₁ at temperature T₁ is dropped into water of mass m₂ at T₂ inside a calorimeter. Heat flows from the hot body to the cold one until they reach equilibrium; the T(t) graph for both bodies and the heat Q released = Q absorbed = mcΔT update continuously. With ice, you can clearly see the flat 0 °C segment while it melts (latent heat of fusion). Drag the T₁ and T₂ sliders to try again.
Lesson: Internal energy, heat, specific heat capacity, specific latent heat of fusion, heat balance equation
What it shows
When a hot object is placed in cooler water inside an insulated calorimeter, energy is transferred as heat from the hotter body to the cooler one until both reach the same temperature. With no losses, the heat released equals the heat absorbed and each body obeys Q = mcΔT, so the final temperature is a weighted average that lies closer to the body with the larger heat capacity mc. When the object is ice at 0 °C, energy first goes into melting it, Q = mλ with λ the specific latent heat of fusion, without any rise in its temperature.
How to use
With the default aluminum object at 100 °C and water at 20 °C, predict the equilibrium temperature from the heat balance equation, then watch the T(t) graph. Change Material of object 1 to copper or iron with the same masses and temperatures to see the effect of specific heat capacity. Then choose ice at 0 °C and look for the flat part of its curve while it melts. Varying Mass of water shows how a larger water mass limits the temperature change.
Parameters you can change
- Mass of object 1 0.1–5 kg
- Material of object 1 Aluminum (c = 880 J/kg·K), Copper (c = 380 J/kg·K), Iron (c = 460 J/kg·K), Water (c = 4200 J/kg·K), Ice at 0 °C (λ = 334 kJ/kg)
- Initial temperature of object 1 0–100 °C
- Mass of water 0.1–5 kg
- Initial temperature of the water 0–100 °C
Questions to explore
- Why does the equilibrium temperature end up much closer to the water's starting temperature when object 1 is a metal?
- With the same mass and starting temperature, does copper or aluminum warm the water more, and why?
- What does the flat section at 0 °C on the ice curve show about where the absorbed energy goes?
