Changes of State Chapter 3 Section 2

Changing State By removing or adding energy, a substance can lose or absorb energy, its temperature can change, its state can change, and the speed of its particles can change.

Changes of State

State of Matter

Melting The temperature at which a substance changes from a solid to a liquid is its melting point. Melting is an endothermic change. A substance absorbs energy during an endothermic change. heat inside

Freezing The temperature at which a liquid changes into a solid is its freezing point. Freezing of any substance occurs when a liquid changes to a solid. A substance loses energy during an exothermic change. Freezing is an exothermic change. heatoutside

Turn to your partner and summarize The difference between a endothermic and exothermic reaction in relation to energy

Comparing Changes of State

Vaporization The particles of water that evaporate from an open container have more speed and higher energy than the particles that remain. Water enters the atmosphere through the process of vaporization. It is an endothermic change. Boiling is vaporization that occurs throughout a liquid. Boiling changes a liquid to a gas. Perspiration: Public Service Announcement

A second form of vaporization is evaporation. Evaporation is vaporization that occurs at the surface of a liquid

Condensation Condensation is when a substance in a gaseous state changes to a liquid state. For a substance to change from a gas to a liquid, particles must clump together. Water redeposit into lakes in the form of rain by condensation. Water forms on the outside of a glass of cold lemonade as a result of condensation. Condensation is an exothermic change.

Sublimation The change of state from a solid straight to a gas is called sublimation. Energy must be added for sublimation to occur, so it is an endothermic change. Solid carbon dioxide (dry ice) is a great example of a substance that undergoes sublimation.

Comparing Changes of State Freezing and melting occur at the same temperature.