EVERYDAY SCIENCE

Detailed explanation-1: -All phase changes are accompanied by changes in the energy of a system. Changes from a more-ordered state to a less-ordered state (such as a liquid to a gas) are endothermic. Changes from a less-ordered state to a more-ordered state (such as a liquid to a solid) are always exothermic.

Detailed explanation-2: -All phase changes require a gain or a loss of heat energy. The energy change allows the particles to have a new arrangement, thereby creating a new phase. These phase changes can only happen at certain fixed temperatures for each type of substance.

Detailed explanation-3: -Energy is required to melt a solid because the bonds between the particles in the solid must be broken. Since the energy involved in a phase changes is used to break bonds, there is no increase in the kinetic energies of the particles, and therefore no rise in temperature.

Detailed explanation-4: -Condensation is the reverse process, where heat in transferred away from a substance to its surroundings. This release of latent heat increases the temperature of the surroundings. Energy must be removed from the condensing particles to make a vapor condense.

Detailed explanation-5: -during a change of state, but the energy of a substance does change. Some changes of state require energy. Changes of state that require energy are melting, evaporation, and sublimation. Energy is released in some changes of state.