View source for Standard Temperature and Pressure

==Key Stage 3==
===Meaning===
'''Room Temperature''' is around 20°C.

===About Room Temperature===
: '''Room Temperature''' is used to describe when a [[substance]] has a particular [[State of Matter|state of matter]].
: When stating that [[Iron]] is a [[solid]] we assume the person stating it means at '''room temperature''' because that's the [[temperature]] [[human]]s are comfortable in. In reality [[Iron]] can be a [[solid]], [[liquid]] or [[gas]] depending on the [[temperature]].
: The [[State of Matter|state]] of [[element]]s on the [[Periodic Table]] are given at '''room temperature'''.

==Key Stage 4==
===Meaning===
'''Standard Temperature and Pressure''' is around 20°C and 101,000Pa.

===About Standard Temperature and Pressure===
: '''Standard temperature''' or '''room temperature''' is around 20°C because that is the [[temperature]] [[human]]s are most comfortable in.
: '''Standard pressure''' is around 101,000Pa of [[Atmospheric Pressure|atmospheric pressure]] because that is the [[pressure]] on our bodies when we are at [[Sea Level|sea level]].
: '''Standard temperature and pressure''' is used to describe whether a [[substance]] is a [[solid]], [[liquid]] or a [[gas]] under normal conditions.
: [[Substance]]s can change their [[State of Matter|state of matter]] depending on the [[temperature]] and [[pressure]] around them. So when stating something as a [[solid]], [[liquid]] or [[gas]] it's important to note the [[temperature]] and [[pressure]] at which this is true.

===Examples===
: [[Water]] is a [[liquid]] '''STP''' (At standard temperature and pressure). If the [[pressure]] is reduced to zero then [[water]] becomes a [[gas]].
: [[Oxygen]] is a [[gas]] '''STP'''. Increasing the [[pressure]] or decreasing the [[temperature]] of [[Oxygen]] can cause it to become a [[liquid]].