Review from last time…

Atom, Molecule, Compound, Element? Molecule (element) O Xe O O H C C H O H Atom (element) H Molecule (compound) H O C O O C H H H H H Molecule (compound) Molecule (compound) Molecule (compound)

What is the formula of each of these? Xe O O H C C H O2 ”Oxygen” O H Xe “Xenon” H C2H4O2 “Acetic acid” H O C O O C H H H H H CO2 “Carbon dioxide” H2O “Water” CH4 “Methane”

More atomic history… John Dalton – 1800s Democritus Aristotle (Indivisible, (Divisible, Discontinuous) Continuous) John Dalton – 1800s

All matter is made of atoms (indivisible). More atomic history… All matter is made of atoms (indivisible). Atoms of the same element are identical. Atoms of different elements are different ! John Dalton – 1800s

Counting atoms H2SO4 These are subscripts (small numbers). They indicate the quantity of the atom that appears immediately before the number.

Counting atoms Ca(OH)2 Sometimes a subscript will appear after brackets. This means that all atoms inside the bracket are multiplied by this number.

Counting atoms Ca3(PO4)2 Al2(SO4)3

Counting atoms 3 Mg(NO3)2 This is a coefficient. When a coefficient appears before a compound, you must multiply the number of each of the atoms in the compound by this number.

Counting atoms Workbook p. 6

Chemical Reactions In a chemical reaction, the atoms in molecules are rearranged. The items we start with are called reagents. When the reaction is over, we get products +

Chemical Reactions Chemical reactions must obey the law of conservation of mass! Propane + oxygen carbon + water dioxide 82.3 g 11.2 g 27.9 g ?

Chemical Reactions H2SO4 + CuO CuSO4 + H2O C3H8 + 5 O2 4 H2O + 3 CO2 54.2 g ? 79.7 g 3.4 g C3H8 + 5 O2 4 H2O + 3 CO2 26 g 17 g 32 g ?

Chemical Reactions C3H8 + 5 O2 4 H2O + 3 CO2 The number of atoms on the reagents side MUST equal the number of atoms on the products side.

Chemical Reactions C3H8 + 5 O2 4 H2O + 3 CO2

Chemical Reactions

Chemical Reactions Workbook p. 13-14