Further heating then adds energy to the liquid particles, increasing their speed, kinetic energy, and temperature. This is the second slope on the curve. Once the particles are energetic enough to completely break free of each other, they start to enter the gas phase. Boiling occurs at the second plateau of this curve, and the temperature at this point is referred to as the boiling point . Again, the added heat is being used to break up the interactions between particles instead of increasing their kinetic energy, so no temperature increase is observed until all particles are in the gas phase. Finally, adding even more energy will further speed up the gas particles, increasing the kinetic energy and temperature of the substance.
Ann put some broth on the stove to heat up. After putting the lid on she turned the heat on and started dicing vegetable. After awhile she checked the broth and saw it was starting to boil but just then she heard a knock at the door so she put the lid back on and went to answer it. When she returned 20 minutes later the broth had boiled away.
Did heating the broth increase or decrease the temerature?