Entropy tracks how energy spreads and how processes become irreversible.

Entropy is a state function that helps predict the direction of natural processes.

• Entropy as a property of state
• Energy dispersal / spreading (conceptual)
• Why “disorder” is an incomplete shorthand

For a reversible process, entropy change is defined by dS = δQrev / T and can be computed along a reversible path.

• What “reversible” means operationally
• Role of temperature in entropy change
• Why you can choose a convenient reversible path

“Disorder” can be a helpful intuition, but entropy is better understood as counting accessible microscopic possibilities and energy spreading.

• Why “messy room” analogies break
• Microstate intuition (conceptual)
• Connecting entropy to irreversibility

For an isolated system, entropy never decreases. It increases for irreversible processes and stays constant only for reversible ones.

• What “isolated” means (no heat/work exchange)
• Entropy production as a marker of irreversibility
• Examples: mixing, friction, heat flow

Practice computing ΔS in simple reversible cases and reasoning about signs of entropy change in real processes.

• Compute ΔS for simple heat-transfer steps
• Classify processes as reversible/irreversible (intro)
• Sign reasoning for isolated-system scenarios
• Concept checks on “disorder” misconceptions
• Exam-style entropy interpretation sets