3-3

Melting point

A point when a solid melts

Boiling point

A point when the liquid turns to gas.

Heat of fusion

Amount of energy absorbed as it melts

how much energy does water release as it freezes

334 joules

Freezing point

A Point when the liquid freezes

Melting

As solid particles gain energy, the molecules start to vibrate more quickly. At the melting point, some molecules overcome the forces of attraction. Energy gained after the the solid melts increases the average kinetic energy or the temperature.

Name exothermic changes

Freezing; condensation; Deposition

How does the energy of a system change during a phase change?

Energy is either absorbed or released during a phase change

What is the difference between evaporation and boiling?

Evaporation takes place at the surface of a liquid and occurs at temperatures below boiling point.

Name six common phase changes

Melting; Freezing; vaporization; condensation; sublimation; deposition

Name endothermic changes

Melting; Vaporization; Sublimation

Deposition

Phase when a gas or vapor changes directly into a solid.

Phase change

Reversible physical change that occurs when a substance changes from one state of matter to another

Vaporization

Substance absorbing energy in order to change from liquid to gas.

Which substances freeze at higher temperature?

Substances that are solids at room temperature.

What happens to the temperature of a substance during a phase change?

Temperature of a substance does not change during a phase change.

Heat of vaporization

The amount of energy liquid gains when it vaporizes

What happens to the arrangement of water molecules as water melts and freezes?

The arrangement of molecules in water become less orderly as water melts and more orderly as water freezes.

What does the boiling point of a substance depend on?

The atmospheric pressure; lower the atmospheric pressure the lower the boiling point.

Endothermic change

The system absorbs energy from its surroundings

Exothermic change

The system releasing energy to its surroundings.

Vapor pressure

The pressure cause by the collisions of vapor and the walls of enclosed container container

Similarity between melting and freezing point

They are equal

when will water evaporate fast?

Water will evaporate faster when the container has a greater surface area.

Freezing

When liquid is freezing the energy flows out the the liquid. As the kinetic energy decreases, they move more slowly. At the freezing point, some molecules move slowly enough for the attractions between molecules to have effect. Any energy removed from solid after phase change will mean decrease in kinetic energy or temperature.

Condensation

When substance changes from gas or vapor to a liquid..

When does liquid boil?

When the atmospheric pressure is equal to the vapor pressure.

Vapor

gaseous phase of a substance that is normally a solid or a liquid at room temperatures.

heat of fusion for water

one gram of ice absorbs 334 joules (J)

Heat of vaporization of water

one gram of water gains 2261 joules of energy

Sublimation

phase that change from a solid to a gas or vapor

Evaporation

process that changes a substance from a liquid to a gas at temperatures below the substance's boiling point.