[B] Effect of change of Pressure –
By increasing pressure, particles of matter can be brought close together. When we apply pressure on a gas enclosed in a cylinder, it starts compressing and converts into liquid. Thus, by applying pressure and reducing temperature a gas can be liquefied.
Example – Carbon dioxide is a gas under normal conditions of temperature and pressure. It can be liquefied by putting pressure at ordinary temperature. Solid carbon dioxide (CO2) is stored under high pressure. Solid CO2 gets converted directly to gaseous state on decrease of pressure to 1 atmosphere without coming into liquid state. This is the reason that solid carbon dioxide is also known as dry ice.
Thus, pressure and temperature determine the state of a substance i.e. solid, liquid or gas.
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