Chemistry I Honors Northwestern High School Jeff Venables Chemical Reactions Chemistry I Honors Northwestern High School Jeff Venables

Chemical Equations Reactants → Products Reactants – the starting materials in a chemical reaction Products – the ending materials in a chemical reaction What happens during a chemical reaction?

Evidence of a chemical reaction: Color Change Heat Change Solid Forms (precipitate) Gas Forms (bubbles)

Symbols used in Chemical Equations + separates two reactants or two products → “yields” – separates reactants from products (s), (l), (g), (aq) – states of substances indicates heat is added indicates a catalyst is used

Balancing Chemical Equations Law of Conservation of mass In a chemical reaction, atoms are “rearranged.” There must be the same number of atoms of each element on each side of the equation (reactants and products) Count atoms, then change coefficients, if necessary, to balance the equation.

2 H2 (g) + O2 (g) → 2 H2O Subscripts (cannot be changed) Coefficients

Examples – Balance the following equations KClO3 → KCl + O2 N2 + H2 → NH3 Ca3(PO4)2 + NaOH → Na3PO4 + Ca(OH)2 K + H2O  KOH + H2

Examples – Balance the following equations 2KClO3  2KCl + 3O2 N2 + 3H2  2NH3 Ca3(PO4)2 + 6NaOH  2Na3PO4 + 3Ca(OH)2 2K + 2H2O  2KOH + H2