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All chemical substances are either solid, liquid or gas. To make comparisons easier, the chemistry community has agreed on a concept called "the standard state." The standard state of a chemical substance is its phase (solid, liquid, gas) at 25.0 °C and one atmosphere pressure. This temperature/pressure combo is often called "room conditions."
Two elements are liquid in their standard state: mercury and bromine.
Eleven elements are gas in their standard state. All of the noble gases (He, Ne, Ar, Kr, Xe, Rn) as well the halogens flourine and chlorine. Hydrogen, oxygen and nitrogen are the others.
All other elements are solid in their standard state.
Some Interesting facts about elements:
1) Bromine's boiling point is 58.8 °C. Suppose you have a closed bottle of bromine liquid at 25 °C (room temperature). When you open the bottle, quite a bit of bromine vapor will be released. To get the idea, imagine a small puddle of water on the counter. Eventually, the puddle will all evaporate, even though the temperature never changed from 25 °C. In any event, when the ChemTeam was in high school chemistry (taken his junior year, 1968-69), he spied a bottle of bromine and wondered what it smelled like. Aha, the teacher is at the other end of the room, talking to someone. The ChemTeam grabbed the bottle, whipped the cap off and took a tenative sniff through the nose. Instant, major pain. Gagging. Great pain in the nose. Burning eyes. Did I mention the pain? Quickly, the cap was replaced and seat taken, with an innocent look plastered on the face. Man, that hurt!!
2) Iodine is a solid at room temperature, but it sublimes quite easily. This means it changes from solid directly to gas without going through the liquid state. Dry ice (solid carbon dioxide, which is not an element) does the same thing.
3) Mercury is a liquid AND a metal. That means it conducts electricity very easily. You might want to find out what a mercury switch is. The reasons why mercury is a liquid are complex, but evidently involve aspects of relativity (as in Albert Einstein).
4) Gallium is a solid at room conditions, but its melting point is just under 30 °C. In the past, a small amount of gallium was used to plug fire sprinklers, but I don't think gallium is used any more. Cesium has a melting point of 28.4 °C and I know for sure it is not used for fire sprinklers. Some atomic clocks (accurate to about one second in 3000 years) have used a "cesium fountain" as a timing device.
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