1. Chemical Reactions G.Burgess 2006

2. Chemical Reactions • Occur when atoms of substances join other atoms of other substances to form different chemical materials • There are several types of chemical reactions • Chemists show chemical reactions symbolically as chemical equations

3. Chemical Equations Products Reactants NaOH(aq)+ HCl(aq) NaCl(aq) + H2O(l) Molecular formula of compound State (aq) = aqueous/ in water (l) = liquid **the ‘+’’s means “reacts with” **the arrow between the reactants and products means “to give”.

4. Types of chemical reactions • Formation(synthesis): when two pure substances combine to make a new substance ie. 2H2 + O2 2H2O 2. Decomposition: when a compound breaks up into its individual parts. ie. 2H2O 2H2 + O2

5. Types of chemical reactions • Single displacement: when one element is removed from a molecule and replaced by another element. ie. 2Fe + 6HCl 2FeCl3 + 3H2

6. Types of chemical reactions • Double displacement: When 2 molecules switch elements. AgNO3 + HClAgCl + HNO3

7. Review • Fe + S FeS • 2 Mg + O2 2 MgO • Na2O + H2O 2 NaOH • CuCO3 CuO + CO2 • Fe + H2SO4 FeSO4 + H2 • AgNO3 + NaCl AgCl + HNO3

8. Answers to review • Synthesis • Synthesis • Synthesis • Decomposition • Single Displacement • Double displacement

9. Rules of chemical reactions • Law of conservation of matter: • The number of atoms of each element produced is the same as the number of atoms in the reactants. ie. H2 + O2 H2O 2H2 + O2 2H2O Creating a balanced equation helps demonstrate this law.

10. Balancing Chemical Equations • All chemical equations must demonstrate the Law of conservation of matter. • Begin by balancing the metals • Then Poly atomic ions • Then non-metals • Then hydrogen • Lastly, balance oxygen.

11. Balancing Chemical Equations Example: Al + O2 Al2O3 • Al on the left = 1; Al on the right = 2. Put a 2 in front of the Al on the left. 2Al + O2 Al2O3 2. O on the left = 2; O on the right = 3. Put a 3 in front of O on the left and 2 in front of Al on the right. 2Al + 3O22Al2O3 NOTICE: The Al’s do not match. To balance the Al’s use a multiple of all three numbers (2Al=2; 2Al2=4) Since Al = Al1 and 1*4 = 4. then the balanced formula is… 4Al + 3O22Al2O3 **Now we have 4Al’s and 6O’s on each side.

12. Review • S + H2SO4 SO2 + H2 • NaCl + BeF2 NaF + BeCl2 3. Ca(OH)2(aq) + HCl(aq) CaCl2(aq) + H2O(l) 4. CH4 + O2 CO2 + H2O 5. Mg + Mn2O3 MgO + Mn