Chemistry Regents Practice Test

The correct answer is Gallium. At standard atmospheric pressure (1.0 atmosphere), Gallium has a melting point of approximately 302.9 K, which means it transitions from solid to liquid around this temperature. Therefore, at 305 K, Gallium exists in a liquid state. Mercury also exists as a liquid at this temperature, as its melting point is around 234 K, making it stable as a liquid under these conditions. Water, while it is liquid at 305 K (32 °C) and 1.0 atmosphere, is not a single element but rather a compound (H₂O). Bromine is a common nonmetal element that is indeed a liquid at room temperature, but its boiling point is higher than 305 K, making it a solid at that temperature and pressure. Each of these substances behaves according to its unique physical properties, which is why Gallium is correctly identified as the liquid element under the specified conditions.