Changes in Matter

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

Representing Change By the Way 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!

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) =

Dissolving source

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)

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) 

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

2H2O(l)  2H2(g) + O2(g)

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 don’t match!

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) Formulas don’t match! source

Other Chemical Changes Cooking Fermentation Corrosion Rotting Explosion Synthesis

Evidence of Chemical Change Produce Heat Produce Light Evolution of a Gas Formation of a Precipitate Change in Properties …meaning… Create something NEW

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