As heat is added to a solid material, the particles of the solid begin to vibrate faster. At a certain temperature, they begin to slide past each other and the material melts. If the material is heated further, some of the particles obtain enough kinetic energy to break their bonds to other particles and they enter the vapor phase. As more heat is added, particles enter the gas state at a faster rate. When the pressure of the surrounding air is equal to the pressure of the vapor, boiling begins and vapor bubbles can form inside the material instead of just at the surface. At the boiling point, heat energy added to the material is used to break intermolecular bonds and create gas vapor, so boiling occurs at a constant temperature.

Questions

1. Temperature is related to the average kinetic energy of the particles of the material. During a phase change, the temperature of the material is constant. (For example, ice melts at zero Celsius.) What does that imply about the average kinetic energy of the particles in each of the two phases?
.
2. Usually, adding heat to a substance causes the particles to increase in kinetic energy and the temperature rises. Since that does not happen during a phase change, where does the heat energy go?
3. Why is the energy needed to convert a liquid to a gas usually very much larger than the amount of energy needed to convert a solid to a liquid?
4. A radiator or pressure cooker allows a liquid to achieve a higher temperature than normal boiling by sealing off the system from the surroundings. Based on the definition of boiling and this animation, how is that possible?