The liquid and gaseous states of water can co–exist at ________.

100^oC is the boiling point of water, i.e. it is the temperature at which liquid starts boiling at the atmospheric pressure. Therefore, at this temperature both liquid and gaseous states of water can co–exist. Once boiling point is reached, the temperature of the system will remain constant until all water changes to gaseous state because the heat supplied is used to overcome the forces of attraction between particles of water so as to change it into gaseous state. At 99^oC, water will exist in liquid and at 101^oC, water will exist in gaseous state. At 0^oC (i.e. Melting point of ice) both ice and water will co-exist as at this temperature, ice starts melting. The heat supplied is used to overcome the forces of attraction between the particles so as to convert it into liquid state. The temperature will remain 0^oC until all the ice changes into liquid and therefore, at 0^oC, both solid and liquid states will co-exist.