At low pressures, the range of temperature for a liquid to exist is smaller. That is why water boils at less than 100 O C at high altitudes. If the pressure is low enough, the liquid phase does not happen. This is further examined by using phase diagrams . A pure liquid contains only one substance.
Most liquids dissolve other substances.
The liquid is the solvent and the substance being dissolved is the solute . The resulting mixture is called a solution . Water is an excellent solvent. They are said to be soluble in water. Many substances do not dissolve in water.