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Thermodynamics · Quick Reference
Heat Cheat Sheet
In one line: 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.
Key Ideas
1Heat vs. Temperature. Temperature measures average particle kinetic energy; heat is the actual thermal energy transferred between objects due to a temperature difference.
2Direction of Heat Flow. Heat always flows spontaneously from a higher-temperature object to a lower-temperature object, never the reverse (without external work).
3Specific 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.
4Heat 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.
5Methods of Heat Transfer. Conduction (through direct contact), convection (through fluid movement), and radiation (through electromagnetic waves, no medium needed).
Worked Examples
Find the heat needed to raise 2 kg of water (c=4200 J/(kg*°C)) by 10°C.
84,000 J
A 0.5 kg metal block (c=900 J/(kg*°C)) absorbs 4500 J of heat. Find its temperature change.
10°C
Why does a metal spoon in hot soup feel hot to touch quickly, while a wooden spoon does not?
Metal has much higher thermal conductivity than wood, so heat conducts through it (and into your hand) more quickly
Formulas
Q = m*c*delta_T
Practice Yourself
Find the heat to raise 1 kg of water (c=4200) by 5°C.
21,000 J
A 2 kg block (c=500) absorbs 5000 J. Find its temperature change.
5°C
What is the main difference between heat and temperature?
Temperature is average particle kinetic energy; heat is energy transferred due to a temperature difference