Regents Chemistry June 2026 16 What happens to the energy of the molecules in a liquid sample of a substance as it solidifies at its freezing point? (1) Potential energy and average kinetic energy both decrease. (2) Potential energy and average kinetic energy both increase. (3) Potential energy decreases and average kinetic energy remains constant. (4) Potential energy remains constant and average kinetic energy increases. Solution: As a substance turns from liquid to solid,

Regents Chemistry June 2026 15 At STP, which sample contains the same number of molecules as 20.0 liters of N2(g) at STP? (1) 10.0 L of H2(g) (3) 30.0 L of F2(g) (2) 20.0 L of CO2(g) (4) 40.0 L of SO2(g) Solution: STP stands for standard temperature and pressure. At the same temperature and pressure, in order for two samples of gas to have the same number of molecules, they have to have the same volume as well. Since nitrogen gas has a volume of 20L, the gas with the same num