Which phase change is an endothermic process?
Phases and Phase Transitions
| Phase Transition | Change of Enthalpy |
|---|---|
| Vaporization (liquid to gas) | ΔH > 0; enthalpy increases (endothermic process) |
| Sublimation (solid to gas) | ΔH > 0; enthalpy increases (endothermic process) |
| Freezing (liquid to solid) | ΔH < 0; enthalpy decreases (exothermic process) |
Which of the following two phase changes are both endothermic processes?
Freezing and condensation are both exothermic phase changes. d. Melting and sublimation are both endothermic phase changes and need the energy to occur.
Is Melting exothermic or endothermic?
Phases and Phase Transitions
| Phase Transition | Direction of ΔH |
|---|---|
| Fusion (Melting) (solid to liquid) | ΔH>0; enthalpy increases (endothermic process) |
| Vaporization (liquid to gas) | ΔH>0; enthalpy increases (endothermic process) |
| Sublimation (solid to gas) | ΔH>0; enthalpy increases (endothermic process) |
What are the phase changes that are endothermic?
Endothermic phase changes take in heat from the surrounding environment; they include melting, sublimation and boiling. The forces that bind together the atoms and molecules of a given substance determine its melting and boiling points; the stronger the forces, the more heat energy is needed to overcome them.
Which phase change release and absorb energy?
A phase change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat/cooling. Generally the transition will be from one of the first two fundamental states of matter – solid and liquid – to the other.
What happens to the energy added during a phase change-?
Energy is required to change the phase of a substance, such as the energy to break the bonds between molecules in a block of ice so it may melt. During a phase change energy my be added or subtracted from a system, but the temperature will not change. The temperature will change only when the phase change has completed.
What are phase changes is an exothermic change?
An exothermic phase change is one in which molecules become closer together by giving up energy, resulting in a more condensed phase . Of these options, only condensation features molecules becoming more condensed (changing from gas to liquid), meaning it is exothermic.