Transcript Document

Chapter 2: Properties of Matter
2.2 Changes of state are physical changes
Have learned:
-Substances have physical and
chemical properties
-Physical changes do not change a
substance into a new substance
-Chemical changes result in new
substances
To learn:
-How liquids can become solids
-How liquids can become gases,
and gases can become liquids
-How energy is related to changes
in state
Review
• Density is a chemical property – T/F
• F: physical property
• Cutting a carrot in half is a physical change
– T/F
• True
• Silver tarnishing is an example of a physical
change – T/F
Think about dew…
• Water vapor in the air condensing to liquid
water
– on grass and leaves
– on a cold cup
Matter Changes State
•
•
•
•
Solid: fixed volume and shape
Liquid: fixed volume, not shape
Gas: neither fixed volume or shape
Changing states does not change the
substance…what does change?
• Arrangement of the molecules
• Amount of space between them
Solids
• Melting: solid liquid
• Melting Point: lowest
temperature a solid
will melt to a liquid
• Heat up a solid,
particles gain energy
and vibrate
faster…enough to
become liquid…
Liquids
Solids
• Freezing
• Liquid solid
• Solids – frozen at
room temperature
• Cooler temperatures,
particles move less
• Freezing Point - liquid
becomes a solid
• = melting point!
Liquids
Gases
Solids
• Evaporation: Liquid  Gas
• Typically occurs at the surface of a liquid (ie, the molecules on
the outside, not inside)
• Increase temperature, increase energy and motion of the
particles
• Where does liquid water go when it evaporates?
• Sublimation: Solid  Gas
– Ex: dry ice: frozen,
– sublimates to gas
Liquid
• Boiling: Liquid  Gas
• Bubbles contain energetic
water vapor which escapes
• Boiling occurs at a specific
temperature, evaporation
occurs over a range of temps.
Gas
Liquid
Gas
Condensation: Gas  Liquid
Cold glass cools the air around it
The air loses energy, the particles move slower
The particles are attracted to one-another, form
droplets
• Often occurs when moist warm air comes in
contact with a cold surface
•
•
•
•