Questions: Temperature and Thermal Equilibrium

Question 1

A large lake at 10°C and a small cup of water at 100°C are compared. Which contains more total thermal energy?

• A. The cup, because it is at a higher temperature
• B. The lake, because it has far more mass
• C. They have the same energy because energy is conserved
• D. It is impossible to say without knowing the cup material

Answer: (B)

Temperature is an intensive property — it measures the average thermal energy per particle, not the total. The lake contains an enormous number of molecules, each carrying thermal energy, so its total thermal energy vastly exceeds that of the small hot cup. This distinction between temperature (intensive) and total thermal energy (extensive) is fundamental to thermodynamics.

Question 2

Temperature and heat are the same physical quantity, just measured in different units.

• T. True
• F. False

Answer: False

Temperature and heat are entirely different concepts. Temperature is an intensive property describing the average kinetic energy of particles in a system — it does not depend on the amount of material. Heat is energy in transit: it flows from a hotter object to a cooler one during thermal contact. You can raise temperature without adding heat (by doing work on a system), and you can add heat without changing temperature (during a phase change like melting ice).

Question 3

What does the Zeroth Law of Thermodynamics establish, and why is it called 'zeroth' rather than 'first'?

Model answer: The Zeroth Law states that if A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then A and C are in thermal equilibrium. It is called 'zeroth' because it was identified after the First and Second Laws were already named, yet it is logically prior to both — it is what makes temperature a consistent, transitive property and gives thermometry its foundation.

Without the Zeroth Law, thermometers would not work reliably: the whole premise of a thermometer is that it reaches equilibrium with whatever it touches, and its reading can then be compared to readings from other objects. The Zeroth Law formalizes the transitivity of thermal equilibrium that underpins all temperature measurement.