Phase ChangesPhase Changes

Notes on 3.3Notes on 3.3

TemperatureTemperature

Temperature will not change during a phase change.

Once a substance reaches the temperature required for a phase change to happen, the temperature stays at that same point throughout the phase change.

Temperature will not change during a phase change.

Once a substance reaches the temperature required for a phase change to happen, the temperature stays at that same point throughout the phase change.

Energy and change of state

Energy and change of state

Energy is either absorbed or released during a phase change.

During an endothermic change, heat is absorbed. Example: an ice

sculpture melting

Energy is either absorbed or released during a phase change.

During an endothermic change, heat is absorbed. Example: an ice

sculpture melting

FusionFusion

is another word for melting. Heat of fusion is the

energy a substance must absorb in order to change from a solid to a liquid.

The heat of fusion is different for different substances.

is another word for melting. Heat of fusion is the

energy a substance must absorb in order to change from a solid to a liquid.

The heat of fusion is different for different substances.

Energy and Changes of State continued

Energy and Changes of State continued

An exothermic change occurs when a substance releases heat to its surroundings. Freezing is an

example of an exothermic change.

An exothermic change occurs when a substance releases heat to its surroundings. Freezing is an

example of an exothermic change.

EvaporationEvaporation

Evaporation takes place at the surface of a liquid and occurs at temps below the boiling point for that substance.

When water evaporates in a closed container, what collects above the water? The pressure caused by the collisions of

the water vapor and the walls of the container is called vapor pressure.

What happens to the vapor pressure when the temperature is increased? Why?

Evaporation takes place at the surface of a liquid and occurs at temps below the boiling point for that substance.

When water evaporates in a closed container, what collects above the water? The pressure caused by the collisions of

the water vapor and the walls of the container is called vapor pressure.

What happens to the vapor pressure when the temperature is increased? Why?

CondensationCondensation

Condensation is the phase change where a gas or vapor changes into a liquid.

This is an exothermic process.

Examples include: The moisture on the

mirror after a shower Morning dew on the grass

Condensation is the phase change where a gas or vapor changes into a liquid.

This is an exothermic process.

Examples include: The moisture on the

mirror after a shower Morning dew on the grass

Deposition Deposition

When a gas or vapor changes directly into a solid without first changing into a liquid, deposition has occurred. This is an exothermic change. This is what causes frost to form

on windows.

When a gas or vapor changes directly into a solid without first changing into a liquid, deposition has occurred. This is an exothermic change. This is what causes frost to form

on windows.

D. Density 1. Amount of mass in one unit of volume. (Mass/volume)

D. Density 1. Amount of mass in one unit of volume. (Mass/volume)

2. Measured in kilograms per cubic meter. (Kg/m cubed)

2. Measured in kilograms per cubic meter. (Kg/m cubed)