Temperature is defined through equilibrium, not intuition.

Temperature labels thermal state: it predicts the direction of heat flow when systems are placed in contact.

• Temperature vs “hotness” intuition
• Heat flow direction as an operational test
• Macroscopic state variable viewpoint

If A is in thermal equilibrium with B, and B with C, then A is in thermal equilibrium with C. This allows a consistent temperature scale.

• Equilibrium as a transitive relation
• Why “temperature” must exist
• Thermometer logic

Systems in thermal contact can exchange energy as heat. Equilibrium is reached when no net heat flow occurs.

• Thermal contact vs insulation
• What “no net heat flow” means
• Timescales and practical equilibrium

Thermometers rely on a measurable property that changes reproducibly with thermal state (e.g., volume, resistance). Scales map those readings to numbers.

• Thermometric properties (examples)
• Calibration and fixed points
• Celsius, Kelvin, Fahrenheit (conceptual)

Practice distinguishing temperature from heat, using equilibrium logic, and interpreting thermometer setups.

• Zeroth-law reasoning questions
• Heat-flow direction concept checks
• Thermal contact vs insulation scenarios
• Scale conversion drills (C/F/K)
• Exam-style equilibrium prompts