What is the change of state of evaporation?
Changes of state are physical changes. They occur when matter absorbs or loses energy. Processes in which matter changes between liquid and solid states are freezing and melting. Processes in which matter changes between liquid and gaseous states are vaporization, evaporation, and condensation.
These energy exchanges are not changes in kinetic energy. They are changes in bonding energy between the molecules. If heat is coming into a substance during a phase change, then this energy is used to break the bonds between the molecules of the substance. The example we will use here is ice melting into water.
- Changing the amount of heat energy usually causes a temperature change. However, DURING the phase change, the temperature stays the same even though the heat energy changes. This energy is directed into changing the phase and not into raising the temperature.
- These are called the states of matter. Matter can change from one state to another if heated or cooled. If ice (a solid) is heated it changes to water (a liquid). This change is called MELTING. If water is heated, it changes to steam (a gas).
- A phase change is occuring; the liquid water is changing to gaseous water, or steam. On a molecular level, the intermolecular forces between the water molecules are decreasing. The heat is providing enough energy for the water molecules to overcome these attractive forces.
Do phase changes rearrange the molecules of a substance? Phase changes do not, so we call this a physical change, rather than a chemical change. A phase change requires ____ or ____ energy from a system. The transfer of energy from an object at a higher temperature to an object at a lower temperature.
- Do phase changes rearrange the molecules of a substance? Phase changes do not, so we call this a physical change, rather than a chemical change. A phase change requires ____ or ____ energy from a system. The transfer of energy from an object at a higher temperature to an object at a lower temperature.
- The temperature of the substance does not change during melting, boiling or freezing, even though energy is still being transferred. The temperature also stays the same while a liquid freezes, even though heat energy is still being released to the surroundings.
- These phase changes can only happen at certain fixed temperatures for each type of substance. Changes in phase from solid to liquid (melting) and from liquid to gas (boiling) require energy. When solid ice melts and becomes a liquid, the particles of the substance move farther apart and heat energy is gained.
Updated: 18th November 2019