Aim: How are physical and chemical changes different?

1
Aim How are physical and chemical changes
different?

• Aim Look at the picture below. List as many
  properties of the object in the picture as you
  can.

2
What is a physical property?

• Properties that can be observed without the
  production of new substances. These properties
  include
• Color, shape, phase, solubility (does it
  dissolve), density, melting point, boiling point,
  hardness, taste, weight, conductivity,
  malleability (does it bend), ductility (can it be
  made into a wire), volume, mass, etc
• A physical change is a change in the physical
  characteristics of the sample. Physical changes
  can be reversed.

3
What is a chemical property?

• The ability to undergo a specific chemical
  change. Chemical properties can only be observed
  during a chemical change. During a chemical
  change, the composition of matter always changes.
  These changes cannot be reversed by ordinary
  means. Chemical changes are also known as
  chemical reactions.

4
Part of a Chemical Reaction

• Reactant the substance that is present at the
  beginning of the reaction.
• Product the substance produced as a result of
  the reaction.
• Example
• Baking Powder Vinegar ?Water Carbon Dioxide
• Reactants Products

5
How can we recognize whether a chemical change
has occurred?

• Signs to look for
• The transfer of energy (heat has been released or
  absorbed).
• A change in color.
• The production of a gas.
• The formation of a precipitate (a solid that
  forms and settles out of a liquid mixture).

6
A Demonstration

• Which sign is released by each reaction that
  tells you if it is a chemical reaction?

7
Activity

• Complete the worksheet you were given.

8
Homework

• Read pages 75-77 Sections 4-7 and 4-8.
• Copy and answer 21 and 22 page 78
• Copy and answer 21-25 page 82.