Chemical Reactions

Reactants vs. Products compounds/elements on the left; they are “reacting” compounds/elements on the right; they are “produced”

Reaction symbol MeaningExample  “yields” what is on the left is transformed to what is on the right. # of atoms of one element on the left must be equal to # of atoms on the right. 2Al 2 O 3  4Al + 3O 2 4 Al 4 Al 6 O 6 O

Reaction symbol MeaningExample ↔ or ⇌ Still read as “yields” However these arrows indicate that the reaction can go either way; it is reversible. When salt dissolves: NaCl ⇌ Na + + Cl - You can get the salt back, so it’s reversible

Blue Fugates of Troublesome Creek

Reaction symbol MeaningExample (s) (l) (g) (aq) These are the states of matter: solid, liquid, gas, aqueous Aqueous – solution in water NaOH (aq) + HCl ( aq)  H 2 O ( l) + NaCl (aq) This reaction takes place in water. We know that there is not precipitate formed or gas evolved.

Reaction symbol MeaningExample ∆ Greek letter “delta” When above a reaction arrow it means that heat is put in the reaction. Can also be on either side of the arrow to show that heat is put in the rxn or given off C 6 H 12 O 6 + O 2  H 2 O + CO 2 + ∆ This shows that when sugar is burned, heat is given off as a product.

Class Data Mass Before (g)Mass After (g)Mass Difference (g)

Law of Conservation of Mass Stated by Lavoisier in the 18 th century Total mass of substances in a chemical reaction does not change Ex: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O 180g glucose + 192g oxygen  264g carbon dioxide + 108g water 372g material before  372g material after amount input = amount output