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.
