When heating water, what happens to the heat energy for the temp to stay the same?
We had to heat up water. Sometimes the water would stay at the same temp for a while then keep going up. Please tell me what happens. And what happens when the heat energy is going up rapidly?
While Eric makes some good points, I think the answer is more dependent on the specific properties of water. While Eric’s answers would hold true for all/most liquids, water is unique in that there is significant hydrogen bonding between hydrogen and oxygen atoms of the molecules.
When boiling water you are consistently adding energy in the form of heat to the system, and the temperature rises. During this stage the water molecules are acquiring more energy and moving around, but still interact with each other by hydrogen bonding. The temperature plateau that is reach occurs when the water molecules are using the acquired energy to overcome the hydrogen bonding. Finally, when the temperature increases again, it is for the water molecules to vaporize. Therefore, the plateau is the energy required to overcome hydrogen bonding before water changes phase from liquid to gas.
Further proof of this lies in how thermometers measure temperature. They actually monitor the kinetic motion of molecules surrounding them. When molecules become more excited, there are more collisions with the thermometer and this corresponds to a temperature. When hydrogen bonds are being dissociated, the energy is not being converted into motion, but instead going to breaking the bonds, and there is therefore a plateau!
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