Name the elements which become liquid at 303 K, slightly above room temperature.
The correct answer and explanation is:
At 303 K (which is about 30°C), only a very few elements are in the liquid state. The elements that become liquid slightly above room temperature include:
- Mercury (Hg)
- Bromine (Br)
Explanation:
Room temperature is usually considered around 298 K (25°C). At 303 K (about 30°C), the only two elements that naturally exist as liquids are mercury and bromine.
Mercury has a melting point of 234.32 K (-38.83°C), so it is liquid well below room temperature and remains liquid at 303 K. This property makes mercury unique among metals, as almost all other metals are solid at this temperature. Mercury is used in thermometers and barometers because of its liquid state and high density.
Bromine is a halogen and has a melting point of 265.8 K (-7.2°C). At 303 K, bromine is liquid and exists as a reddish-brown volatile liquid. It is the only nonmetal element that is liquid near room temperature. Bromine is used in flame retardants, dyes, and some pharmaceuticals.
Other elements either melt well above this temperature or are gases at room temperature. For example, cesium and gallium melt slightly above room temperature, but their melting points are generally higher than 303 K: gallium melts at about 303 K (29.76°C) — just about room temperature — so it might be considered borderline, but strictly at 303 K, it just becomes liquid. Cesium melts at 301.6 K (28.4°C), also just below 303 K, so it is liquid at 303 K.
To summarize, mercury and bromine are the main elements liquid at or just above room temperature. Gallium and cesium also become liquid slightly below or near 303 K, making them relevant as well.
This unique liquid state near room temperature makes these elements very useful in scientific, industrial, and technological applications.