Download Physical and Chemical Changes

Physical and Chemical Changes
A physical change is one in which one makes a different
form of the same substance. Physical changes are
usually easily reversed. Example: Solid water  Liquid
Physical Change
Whole piece of glass  shattered pieces of glass
Physical Change
Salt added to water and stirred to make a salt water
solution. Salt + water  salt water solution.
Reversed by distillation.
Chemical Change
A chemical change is a change that makes a new
substance with different properties than the original
substances. Colour changes indicated chemical changes.
Chemical changes are NOT easily reversed.
Chemical Changes
Changes causing temperature change or causing a
change in state (production of a gas – bubbles)
indicates a chemical change. Example
Calcium + water  hydrogen gas + calcium hydroxide
+ heat
Chemical Change
Chemical changes are NOT easily reversed.
Cake batter ingredients + heat  cake
Energy in Changes
When a change gives off energy to the surroundings,
the change is said to be exothermic.
Substance A  Substance B + energy
Endothermic changes
When a change absorbs or soaks up energy, the
change is said to be endothermic.
Substance A + energy  Substance B
Endothermic and Exothermic Changes of State
When energy must be added to make a change, the change is
endothermic.
When energy m,ustA
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