Change of State Notes

• A change from one state of matter to another involves a gain or loss of energy.

• Ice melting = solid to liquid

Characteristics of Solids, Liquids,and Gases

http://www.chem.purdue.edu/gchelp/liquids/character.html

Solids Definite shape

Definite volume

Vibrate

Rigidly bonded

LiquidsNo definite shapeNo constant volumeTakes shape of its’ containerCircular motion

Gases No definite shape No definite volume Rapid random motionMostly empty space

Plasma consists of a collection of free moving electrons and ions - atoms that have lost electrons.

The kinetic theory states that all matter is in motion.

The temperature = the average kinetic energy of the molecules (in o Celsius)

In English we use o Fahrenheit

o Fahrenheit = (9/5 o Celsius) + 32

http://www.plasmas.org/what-are-plasmas.htm

Change of States

• A solid starts heating up (A) • when it melts, the temperature remains constant

the energy changes it from a solid to a liquid (B)• When it is all liquid it starts to increase temp (C)

until it reaches its boiling point (D) • The temperature remains constant during a phase

change !!

Melting is the change from a solid to a liquid state

• Melting point is the temperature when a solid changes to a liquid. (ice melts)

• During any change of state the temperature remains constant

• The flat section is called a “plateau” on a heating or cooling curve (graph)

During heating ice melts at 0oCand water boils at 100 oC

• Heating curve for water through different states of matter:

• Freezing = liquid to solid

• Melting = solid to liquid

• If you were cooling the water down it freezes at the same temperature as it melts !

Melting point is the same as the freezing point

They occur at the same temperature.

Sublimation is a change from a solid to a gas. Only a few things sublimate like Carbon Dioxide (dry ice) and Iodine

freezing point is 80o

• On a cooling curve, the plateau (the flat section) is the freezing point.

• In this cooling curve you start with a liquid

(1-4 min) • During the plateau it freezes ->changes from a

liquid to a solid (4-11 min) • Then it will continue to cool off after it is all solid• One crystal of this substance would melt at ?

Using the cooling curve below, determine which time interval you would find1. a liquid only, a liquid and a solid, and a solid only2. What is the freezing point of this substance?

oC 80 60

40

20 0 2 4 6 8 10 12 (minutes)