Why does boiling water not increase in temperature when additional heat is applied?

Answer 1

Temperature is just a measure of the amount of energy in a substance. When water is heated to 100C and boils, that means that the molecules have enough energy to make that change of state. You can't add any more energy (heat) to that molecule while in the liquid form because once it reaches that temperature it changes state.

When you are looking at a pot of water heating on the stove, it doesn't just instantly flash in to steam when it reaches a certain temperature. That's because the entire body of water has not reached the boiling point yet, just the molecules that are in direct contact or extremely close to the sides of the pot, which are heated to a temperature above 100C.

However, by increasing the pressure on water (or any substance), you can change the boiling point of it. Water under more pressure than 1 atmosphere would boil at a higher temperature because there is more force holding the molecules together.

Answer 2

Pure water boils @ 212oF at normal atmospheric pressure. So anything above that temperature will cause the water will change to a vapor (steam). That's why if you add heat to boiling water you won't see a rise in temperature of the liquid. If you keep adding heat you'll eventually convert all of the water to a vapor.

Answer 3

Liquids can only absorb as much heat before changing there state. The pressure around the water will dictate how much heat the liquid absorbs before it changes. ie. Mountain cooking is a lot longer than sea level. The cooling system in your car is under pressure so the water/glycol mix can absorb more heat from the engine. Water will boil at room temp under vacuum

Answer 4

When water reaches its boiling point, the added heat energy is used to transform the liquid water into water vapor, instead of increasing the temperature of the water. This is because the heat energy is needed to break the intermolecular bonds holding the water molecules together, transitioning from liquid to gas. Once all the water has been converted to steam, any additional heat energy will raise the temperature of the steam.

Answer 5

The energy that would otherwise go into raising the temperature of the water instead goes into turning the water from a liquid to a gas.

Answer 6

When a liquid is boiling, any additional heat will preferentially be consumed by supplying the energy of vaporization required to boil more liquid, as long as any liquid phase remains.

Answer 7

The heat is used up in the form of the latent heat of evaporation. The energy is used to change the phase from liquid to gas.