Changes in Matter

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Changes in Matter
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Physical Change

• The form or appearance of the sample may change
  but the identity remains the same.
• Crumpling
• Cutting, crushing, grinding,tearing
• Phase changes
• Dissolving

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Representing Change

• Use equations to show change.

Substances Before ? Substances After
By the Way
In a physical change, you have the same stuff
before after. The formulas match!
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Dissolving

• Dissolving is a physical change.
• Think of sugar in water. You still have sugar
  you just spread it out and put water molecules in
  between.
• C6H12O6(s) ? C6H12O6(aq)

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Dissolving
source
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Phase Changes

• Phase changes are physical changes.
• No new substance is created (chemical formula
  stays the same)
• ice melting H2O(s) ? H2O(l)
• water boiling H2O (l) ? H2O(g)

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Chemical Change

• In a chemical change the identity of the matter
  is changed.
• A new substance with unique properties is formed.
• The chemical formula changes.
• Ex 2H2O(l) ? 2H2(g) O2(g)

?
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Chemical decomposition of water.
2H2O(l) ? 2H2(g) O2(g)
Decomposition Reaction where a molecule breaks
down into simpler substances.
source
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2H2O(l) ? 2H2(g) O2(g)
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Burning

• Common name for an oxidation reaction.
• Burning means reacting with oxygen.
• Burning is a chemical change, because the
  original substance is changed into new kinds of
  matter.
• Ex CH4(g) 2O2(g) ? CO2(g) 2H2O(g)

Formulas dont match!
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CH4(g) 2O2(g) ? CO2(g) 2H2O(g)
Formulas dont match!
source
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Other Chemical Changes

• Cooking
• Fermentation
• Corrosion
• Rotting
• Explosion
• Synthesis

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Evidence of Chemical Change

• Produce Heat
• Produce Light
• Evolution of a Gas
• Formation of a Precipitate
• Change in Properties meaning

Create something NEW
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Conservation of Mass

• Mass is neither created nor destroyed.
• Mass is conserved.
• Massreactants Massproducts
• Massbefore Massafter
• of atoms before of atoms after