Section 2 – pg 96 Changes of State Chapter 3 Section 2 – pg 96 Changes of State

Pg 97 Changes of State Change from liquid to gas involves addition of thermal energy Change from liquid to solid involves a decrease in thermal energy

Melting The change in state from a solid to a liquid Pg 97 Melting The change in state from a solid to a liquid In pure substances, the substance melts at a specific point – Melting Point

Pg 97 When a substance melts, the particles in the solid vibrate so fast that they break from their fixed positions.

Freezing Pg 98 The change from a liquid to a solid Reverse of melting When a substance freezes, the particles in the liquid move more slowly that they begin to take on fixed positions

Liquid -> Gas Vaporization: the change from liquid to a gas Pg 98 Liquid -> Gas Vaporization: the change from liquid to a gas Takes place when the particles in a liquid gain enough energy to move independently, forming a gas Evaporation and Boiling

Pg 99 Evaporation Vaporization that takes place only on the surface of a liquid

Pg 99 Boiling occurs when a liquid changes to a gas below its surface as well as at the surface -Boiling Point: the temperature at which a liquid boils -Boiling point depends on the air pressure above it

Pg 100 Gas -> Liquid Condensation: the change in state from a gas to a liquid The reverse of vaporization The particles in a gas lose enough thermal energy to form a liquid

Pg 100 These are not gases, they are water droplets suspended in air

Pg 101 Solid <-> Gas Sublimation: the surface particles of a solid gain enough energy that they form a gas During sublimation, particles of a solid do not pass through the liquid state as they form a gas

Chapter 3 Section 2 Homework pg 101

1A. What happens to the particles of a solid as it becomes a liquid?

1B. How does the thermal energy of solid water change as it melts?

1C. You are stranded in a blizzard 1C. You are stranded in a blizzard. You need water to drink and you’re trying to stay warm. Should you melt snow then drink it or just eat snow?

2A. What is vaporization?

2B. Name the two types of vaporization 2B. Name the two types of vaporization. Tell how they are similar and how they differ.

2C. Why does the evaporation of sweat cool your body on a warm day?

3A. What process occurs as pieces of dry ice gradually gets smaller?

3B. SKIP!