Objectives

1
Section 15-2

• __________________________

2
Objectives

• Identify substances using ____________ properties
• Compare and contrast ________________ and
  ________________ changes
• Identify chemical changes
• Determine how the law of _________________ of
  __________ applies to chemical changes

3
Physical properties

• A physical property is ____________________
  __________________________________________________
  __________________________________________________
  __________________________________________________
  __
• Examples are
• Color
• __________
• Size
• ___________
• Melting point
• _______________

4
Appearance

• A tennis ball can be described by
• Its bright _______
• Its ________ shape
• Its ________ center
• Its _____________
• A soft drink can be described by
• The fact that it is a _____
• Its _________ color
• Its volume

5
What ways could this be described

• __________________________________________________
  __________________________________________________
  __________________________________________________
  __________________________________________________
  ____

6
Behavior

• Some physical properties of materials describe
  the behavior of a material or substance.
• An important property of iron is the
  fact that it is attracted to
  __________
• A property of gold is that it can
  be pounded into ______ 4
  millionths of an inch
  think
• The ability to ______ is an important
  property of liquids

7
Using special properties to separate

• By using a ______, one can
  separate materials by _____
• Prospectors that _____ for
  gold are using the fact that
  gold is usually
  more _______
  than the other materials in
  the stream to separate it out by size
• A lot of recycling plants use
  strong magnets to separate
  scrap ____ from _________

8
Physical change

• When you change some of an objects ____________
  ____________, you do not change the _________ of
  the materials that make it up.

9
Phase changes

• When an substance _______, ______, __________ or
  __________, it undergoes a physical change.
• The addition or removal of ____________ is what
  causes phase changes.
• __________ changes often accompany phase
  changes, but the change of this property does
  ____ _______ the identity of the material

10

• Even though this molten iron is ______, it still
  has the same characteristics of iron

11
Using physical change to separate

• Distillation _________ ___________________________
  __________________________________________________
  _________________________

12
Chemical properties and changes

• A chemical property is a characteristic of a
  substance that indicates whether it can undergo a
  certain chemical change

• __________ is an important chemical property for
  many substances
• _______ sensitivity is another important chemical
  property

13
Detecting Chemical Change

• The change of one substance into __________ is a
  chemical change
• Signs of a chemical reaction include
• ________
• Cooling
• The formation of ________
• The formation of solids

• Some chemical reactions take place slowly (like
  ________) while other take place at a much more
  rapid pace (like the _________ of rocket fuel)

14
Using chemical change to separate

• Silver ____________ in the presence of __________
  compounds in the atmosphere
• The pure silver can be separated out from the new
  compound by adding the tarnished silver to warm
  water with aluminum foil and baking soda

15
Weathering Chemical or Physical change?

• The weathering of the Earths surface is both a
  ________ and __________ change.
• Physical changes include

• The _________ of rocks by ______ ________ cycles
  does not change the make up of the rock so
  therefore it is considered a physical change
• The cutting through and wearing away of softer
  rock by the actions of water is also a physical
  change because the water just _______ away the
  rock taking with it sand and gravel sized pieces
  of the larger rock
• These processes are responsible for the
  ______________ ___________

16

• Chemical changes include
• The ________ of rock by slightly ________ water
• _____________ easily dissolves in acidic water
• When acidic water seeps through limestone and
  some other minerals, it dissolves some of the
  material and takes it away.
• This process is responsible for the formation
  ___________ and the structures found in them

17
Conservation of mass

• By observing a _______ log turn to ________, you
  may be tempted to think that during the chemical
  change that occurred, some ___________ was lost.
• It was not!!! If you gathered all of the
  ________ that formed, _______ that was carried
  away, and _______ that evaporated out when the
  log was hot, you would find that there is exactly
  the ______ amount of mass after the log was
  burned as before the log was burned

18
Conclusion

• What physical properties of a material can use to
  identify it?
• Is melting a solid a chemical or physical change?
• When making diner, what chemical changes are
  occurring?
• If I take this Sundays Inquirer and start a fire
  in my fire place to warm me up for the Eagles
  game, what is going to happen to the mass of the
  newspaper after it has been burned? Were did the
  components that made up the newspaper go?