1 thermodynamics
1.1 phase transitions
1.2 liquids in space
1.3 solutions
thermodynamics
phase transitions
a typical phase diagram. dotted line gives anomalous behaviour of water. green lines show how freezing point can vary pressure, , blue line shows how boiling point can vary pressure. red line shows boundary sublimation or deposition can occur.
at temperature below boiling point, matter in liquid form evaporate until condensation of gas above reach equilibrium. @ point gas condense @ same rate liquid evaporates. thus, liquid cannot exist permanently if evaporated liquid continually removed. liquid @ boiling point evaporate more gas can condense @ current pressure. liquid @ or above boiling point boil, though superheating can prevent in circumstances.
at temperature below freezing point, liquid tend crystallize, changing solid form. unlike transition gas, there no equilibrium @ transition under constant pressure, unless supercooling occurs, liquid crystallize. note true under constant pressure, e.g. water , ice in closed, strong container might reach equilibrium both phases coexist. opposite transition solid liquid, see melting.
liquids in space
the phase diagram explains why liquids not exist in space or other vacuum. since pressure 0 (except on surfaces or interiors of planets , moons) water , other liquids exposed space either boil or freeze depending on temperature. in regions of space near earth, water freeze if sun not shining directly on , vapourize (sublime) in sunlight. if water exists ice on moon, can exist in shadowed holes sun never shines , surrounding rock doesn t heat much. @ point near orbit of saturn, light sun faint sublime ice water vapour. evident longevity of ice composes saturn s rings.
solutions
liquids can display immiscibility. familiar mixture of 2 immiscible liquids in everyday life vegetable oil , water in italian salad dressing. familiar set of miscible liquids water , alcohol. liquid components in mixture can separated 1 via fractional distillation.
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