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📘 Lesson 4 of 10 · Thermodynamics

⚗️ Calorimetry

Calorimetry is the science of measuring heat transfer — by tracking how much heat flows into or out of substances, we can find specific heat capacities, verify energy conservation, and study reactions.

Course progress: 40%

01 Key Concepts

The Principle of Calorimetry

In an isolated system, heat lost by a hotter object equals heat gained by a cooler object -- energy is conserved during the exchange.

Calorimeter

A device designed to measure heat flow during a physical or chemical process, insulated to prevent heat loss to the surroundings.

Setting Up a Calorimetry Equation

Heat lost by the hot substance = heat gained by the cold substance: m1*c1*(T1-Tf) = m2*c2*(Tf-T2), where Tf is the final equilibrium temperature.

Finding an Unknown Specific Heat

By measuring the final equilibrium temperature after mixing a known and unknown substance, you can solve the calorimetry equation for the unknown specific heat.

Heat of Fusion and Vaporization

The heat required to change a substance's phase (like ice to water, or water to steam) without changing its temperature -- this energy goes into breaking molecular bonds, not raising temperature.

02 Key Formulas

03 Solved Examples

Example 1 100g of water (c=4.2 J/(g*°C)) at 80°C is mixed with 100g of water at 20°C. Find the final equilibrium temperature.
  1. Since both masses and specific heats are equal, the final temperature is simply the average.
  2. (80+20)/2.
Answer: 50°C
Example 2 200g of metal at 100°C is dropped into 300g of water (c=4.2) at 20°C, reaching equilibrium at 25°C. Find the metal's specific heat.
  1. Set up: m1*c1*(T1-Tf) = m2*c2*(Tf-T2).
  2. 200*c1*(100-25) = 300*4.2*(25-20).
  3. 200*c1*75 = 300*4.2*5 = 6300.
  4. 15000*c1 = 6300, so c1 = 6300/15000.
Answer: c1 = 0.42 J/(g*°C)
Example 3 Why does the temperature of ice water stay at 0°C while ice is melting, even as heat is continuously added?
  1. The added heat is being used entirely to break the molecular bonds holding the ice in solid form (the heat of fusion).
  2. Only after all the ice has melted does additional heat begin raising the water's temperature further.
Answer: The heat goes into the phase change (melting) rather than raising temperature, until all the ice has melted

04 Practice Questions

150g water at 90°C mixes with 50g water at 10°C. Find the equilibrium temperature.
50°C (simple average since masses/c equal)
2What does a calorimeter measure?
Heat flow during a physical or chemical process
3What is the core principle of calorimetry?
Heat lost by a hotter substance equals heat gained by a cooler substance (in an isolated system)
4What is 'heat of fusion'?
The heat required to change a substance from solid to liquid without changing its temperature
5Why must a calorimeter be well insulated?
To prevent heat loss to (or gain from) the surroundings, ensuring accurate measurements

📄 Calorimetry — Downloadable Worksheet

10 questions with a full answer key. Grab the PDF to print, or try the interactive version in your browser.

🗒 Cheat Sheet ⬇ Download PDF 🖥 Interactive Worksheet