Entropy

TL;DR

• Quantifies how disordered or random a system is.
• Increases when components of a system become more mixed or energy becomes more evenly distributed.
• Used to predict behavior across physical and complex systems.

Definition

Entropy is a measure of the disorder or randomness in a system. It is a fundamental concept in thermodynamics and is used to predict the behavior of many different types of systems, from molecules in a gas to entire ecosystems.

Explanation

Entropy increases when a system moves to a more disordered state because there are more possible arrangements of the system’s atoms or molecules. Processes that mix components or redistribute energy tend to raise entropy by increasing the number of ways the system can be arranged. Entropy therefore provides a way to predict how systems evolve toward more probable, less organized configurations.

Examples

Mixing of two gases

Imagine two different gases, A and B, in separate chambers within a container. Initially, the gases are separated and there is no mixing between them. When the walls between the two chambers are removed, the gases start to mix together, creating a more random and disordered state. This mixing is an example of an increase in entropy, as the gases become more disordered and less organized.

Heat dissipation: hot coffee and ice water

Consider a hot cup of coffee and a cold glass of ice water on a table. Initially, the hot coffee has a higher temperature and the ice water has a lower temperature, creating a temperature gradient. Over time, the temperature of the coffee decreases as it dissipates heat to the surrounding air, and the temperature of the ice water increases as it absorbs heat from the surrounding air. This heat transfer is an example of an increase in entropy, as the energy in the system becomes more evenly distributed and less organized.

Use cases

• Predicting the behavior of gases
• Assessing the efficiency of engines
• Understanding the stability of chemical reactions
• Analyzing the behavior of complex systems such as ecosystems
• Predicting the long-term evolution of the universe

Related terms

• Thermodynamics
• Gases
• Heat transfer / Energy dissipation
• Chemical reactions
• Ecosystems