Suppose you place an ice cube in a beaker of room temperature water, then seal them in a rigid, well-insulated container. No energy can enter or leave the container.
a. If you open the container an hour later, will you find a beaker of water slightly cooler than room temperature, or a large ice cube and some 100°C steam?
b. Finding a large ice cube and some 100°C steam would not violate the first law of thermodynamics. W = 0 J and Q = 0 J because the container is sealed, and ΔEth = 0 J because the increase in thermal energy of the water molecules that became steam is offset by the decrease in thermal energy of the water molecules that turned to ice. Energy would be conserved, yet we never see an outcome like this. Why not?