A supercritical fluid is formed whenever:
- AA substance is heated above its critical temperature
- BA substance is completely burnt
- CA substance is heated far below its critical temperature
- DNone of the above
Show answer and explanation
Correct answer: (a) A substance is heated above its critical temperature
Explanation
Above its critical temperature, a gas cannot be turned into a liquid by any pressure. When a substance is above both its critical temperature and its critical pressure, the liquid and gas become one phase, a supercritical fluid. It flows like a gas but dissolves things like a liquid.
Supercritical carbon dioxide (above 31 °C and 73 atm) is used to decaffeinate coffee and to extract flavours and essential oils.