2 DESCRIBING CHEMICAL CHANGE In a chemical reaction (rxn), one or more substances (reactants) change into one or more different substances (products).reactants productsChemical rxns involve chemical changes.
3 DESCRIBING CHEMICAL CHANGE Reactants change into products:bonds are brokenatoms rearrangenew bonds are formedAtoms themselves are neither created nor destroyed!
4 DESCRIBING CHEMICAL CHANGE baking soda + vinegar → ?In aqueous solution, acetic acid reacts with sodium bicarbonate to produce sodium acetate, carbon dioxide and water.
5 DESCRIBING CHEMICAL CHANGE sodiumbicarbonate+aqueousacetic acidsodium acetate+carbon dioxidewater
6 → → Symbol Explanation + separates one or more reactants or products → yields – separates reactants from products→ ← reversible reaction(s), (l), (g)solid, liquid, gas(aq)aqueous soln – substance dissolved in waterheat or Δheat suppliedPtplatinum is a catalystheat→Pt→
7 CHEMICAL EQUATIONSphysical states of the substances indicated by symbol in parentheses after the formulaC12H O2 → CO H2O(s) (g) (g) (g)
8 CHEMICAL EQUATIONSexample: sulfur burns in oxygen to produce sulfur dioxideS(s) + O2(g) → SO2(g)heat
9 CHEMICAL EQUATIONSexample: when solid potassium is added to water, hydrogen gas and aqueous potassium hydroxide are producedK(s) + H2O(l) → H2(g) + KOH(aq)
10 BALANCING CHEMICAL EQUATIONS burning candle equation:C12H24(s) + O2(g) → CO2(g) + H2O(l)when one molecule of wax reacts, does one molecule of CO2 form?C12H24(s) + 18 O2(g) →12 CO2(g) + 12 H2O(l)181212
11 BALANCING CHEMICAL EQUATIONS: RULES Determine the correct formula for all reactants and products.Write reactants on left and products on right of the arrow.Count the total number of atoms of each element on each side.
12 BALANCING CHEMICAL EQUATIONS: RULES Balance the elements one at a time using coefficients – DO NOT CHANGE SUBSCRIPTSCheck each atom or polyatomic ion to make sure the equation is balanced.
13 BALANCING CHEMICAL EQUATIONS: RULES Make sure all coefficients are in the lowest possible ratio.
14 BALANCE THE FOLLOWING EQUATIONS: SO O2 → SO3Fe2O H2 → Fe H2OP O2 → P4O10Al N2 → AlN
15 BALANCE THE FOLLOWING EQUATIONS: 2 SO O2 → 2 SO3Fe2O H2 → 2 Fe H2O4 P O2 → P4O102 Al N2 → 2 AlN
16 WRITE AND BALANCE (USING MODELS): Hydrogen gas + elemental oxygen yields water.
17 WRITE AND BALANCE (USING MODELS): Solid sulfur + oxygen gas yields sulfur trioxide gas.Nitrogen gas + hydrogen gas yields gaseous ammonia (NH3).