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📘 Lesson 2 of 10 · Thermodynamics

🔥 Heat

Heat is energy in transit — it always flows from a hotter object to a cooler one, and understanding how much heat is needed to change a substance's temperature is essential across science and engineering.

Course progress: 20%

01 Key Concepts

Heat vs. Temperature

Temperature measures average particle kinetic energy; heat is the actual thermal energy transferred between objects due to a temperature difference.

Direction of Heat Flow

Heat always flows spontaneously from a higher-temperature object to a lower-temperature object, never the reverse (without external work).

Specific Heat Capacity

The amount of heat needed to raise 1 kg of a substance by 1°C (or 1K); different materials have very different specific heat capacities.

Heat Transfer Formula

Q = m*c*delta_T, where Q is heat, m is mass, c is specific heat capacity, and delta_T is the temperature change.

Methods of Heat Transfer

Conduction (through direct contact), convection (through fluid movement), and radiation (through electromagnetic waves, no medium needed).

02 Key Formulas

03 Solved Examples

Example 1 Find the heat needed to raise 2 kg of water (c=4200 J/(kg*°C)) by 10°C.
  1. Apply Q = m*c*delta_T = 2*4200*10.
Answer: 84,000 J
Example 2 A 0.5 kg metal block (c=900 J/(kg*°C)) absorbs 4500 J of heat. Find its temperature change.
  1. Rearrange: delta_T = Q/(m*c) = 4500/(0.5*900).
  2. = 4500/450.
Answer: 10°C
Example 3 Why does a metal spoon in hot soup feel hot to touch quickly, while a wooden spoon does not?
  1. Metal is a much better conductor of heat than wood.
  2. Heat transfers via conduction much faster through the metal spoon to your hand.
Answer: Metal has much higher thermal conductivity than wood, so heat conducts through it (and into your hand) more quickly

04 Practice Questions

1Find the heat to raise 1 kg of water (c=4200) by 5°C.
21,000 J
2A 2 kg block (c=500) absorbs 5000 J. Find its temperature change.
5°C
3What is the main difference between heat and temperature?
Temperature is average particle kinetic energy; heat is energy transferred due to a temperature difference
4Which direction does heat always flow spontaneously?
From hotter to cooler objects
5Name the three methods of heat transfer.
Conduction, convection, and radiation

📄 Heat — 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