Topic Cluster

Thermodynamics

Thermodynamics: heat, temperature, entropy and energy transfer — the science of engines, refrigerators and the universe’s arrow of time.

What Is Thermodynamics?

Thermodynamics is the physics of heat, temperature and energy transfer in systems made of enormous numbers of particles — where entropy emerges from the statistics of countless tiny collisions.

Core equations in thermodynamics
Relationship	Equation	What it tells you
Specific heat	Q = m·c·ΔT	Energy to change a temperature
Latent heat	Q = m·L	Energy to change a state
First law	ΔU = Q − W	Energy conservation for a gas
Ideal gas law	P·V = n·R·T	State of an ideal gas
Carnot efficiency	η = 1 − Tc / Th	Best possible heat-engine efficiency
Entropy change	ΔS = Q / T	Disorder gained in a reversible step

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Thermodynamics

Avogadro’s Law (V1/n1 = V2/n2)

Avogadro's law says the volume of a gas follows the amount of gas in it whenever the pressure and temperature hold still, so V1/n1 = V2/n2. Why one mole fills 22.711 L at 100 kPa and 22.414 L at 1 atm, why equal volumes of helium and carbon dioxide weigh 8.006 g and 88.02 g, seven worked problems, three diagrams and an interactive lab.

20 min read

Thermodynamics

Gay-Lussac’s Law (P1/T1 = P2/T2)

Gay-Lussac's law says the pressure of a fixed amount of gas in a rigid sealed container is proportional to its absolute temperature: P1/T1 = P2/T2. The formula, why kelvin is compulsory, gauge against absolute pressure, everyday examples, seven worked problems and an interactive lab.

18 min read

Thermodynamics

Absolute Zero and the Kelvin Scale

Absolute zero is 0 K, which is -273.15 °C and -459.67 °F: the temperature at which a substance has no thermal energy left to give up. The Kelvin scale, the conversions, what molecules do near the floor, why it cannot be reached, worked problems and a live cooling lab.

18 min read

Thermodynamics

What Is the Specific Heat Capacity of Water?

The specific heat capacity of water is about 4186 J/kg per degree Celsius. Here is where that number comes from, why sources disagree, and how to use it.

12 min read

Thermodynamics

The First Law of Thermodynamics

The first law of thermodynamics states that the change in a system's internal energy equals the heat added minus the work done: ΔU = Q − W. Explore 4 thermodynamic processes, 8 worked problems, and an interactive lab.

13 min read

Thermodynamics

What Is Entropy in Physics?

Entropy measures how many microscopic arrangements a system can take, and how widely its energy is spread. This guide covers both entropy formulas, five myths, five real examples and seven worked problems.

14 min read

Thermodynamics

Carnot Efficiency: The Efficiency Ceiling for Heat Engines

Carnot efficiency is the maximum fraction of heat any engine can turn into work, fixed only by the hot and cold reservoir temperatures in kelvin. This guide covers the formula, 8 worked problems, the common mistakes and an interactive simulator.

18 min read

Thermodynamics

What Is the Stefan-Boltzmann Law?

The Stefan-Boltzmann law states that radiated power rises with the fourth power of absolute temperature, so doubling an object's temperature multiplies its output by sixteen. This guide covers the formula, emissivity values, and 7 worked examples.

15 min read

Thermodynamics

Fourier’s Law of Thermal Conduction (Q/t = kAΔT/d)

Fourier's law sets the steady rate of heat conduction through a slab. This guide covers the formula, thermal conductivity values for common materials, and seven worked heat-loss problems.

17 min read

Thermodynamics

Boyle’s Law: Pressure, Volume and the P1V1 = P2V2 Rule

Boyle's Law states that the absolute pressure of a fixed mass of gas is inversely proportional to its volume at constant temperature, so P₁V₁ = P₂V₂. This guide covers the formula, the graph, five real-world examples, four common traps and seven worked problems.

17 min read

Thermodynamics

Charles’s Law Explained

Charles's law states that the volume of a fixed mass of gas at constant pressure is directly proportional to its absolute temperature. Learn the V1/T1 = V2/T2 formula, why kelvin is non-negotiable, and work through eight problems from balloons to hot-air lift.

16 min read

Thermodynamics

What Is the Ideal Gas Law (PV = nRT)?

The ideal gas law, PV = nRT, links a gas's pressure, volume, amount and absolute temperature in a single equation that works for every gas. This guide covers the formula, the molecular reason behind it, eight worked problems, and the four errors that cost the most marks.

17 min read

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