Thermodynamics
7 questions tagged Thermodynamics — spanning every one of the seven Ws.
What Is Entropy?
Entropy is a measure of disorder or randomness in a system; the second law of thermodynamics states that entropy in an isolated system always increases.
Whose law describes the relationship between pressure and temperature at constant volume?
Gay-Lussac’s law. It says that for a fixed amount of gas at constant volume, pressure is proportional to absolute temperature.
Whose law says gas volume increases with temperature if pressure stays constant?
Charles’s law. It states that the volume of a gas is proportional to its absolute temperature at constant pressure.
Whose law is the foundation of thermodynamics and says energy is conserved?
The first law of thermodynamics, developed through the work of James Prescott Joule and others. It states that energy cannot be created or destroyed, only transformed.
Whose work explained how entropy gives heat engines a limit to efficiency?
Sadi Carnot’s work on heat engines. In 1824 he laid the foundations for the second law of thermodynamics.
Why do materials expand when they get hot?
Heating makes atoms and molecules move more vigorously, so they take up slightly more space on average. That is why rails, bridges, and liquids expand with temperature.
Why does the universe have an arrow of time?
Time seems to move in one direction because entropy tends to increase in isolated systems. The universe started in a very low-entropy state, so many processes are irreversible.