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Understanding Chemical Reactions. Physical Science Chapter 10.1 Part 2. Our Story So Far. Think, discuss with partner, discuss with class 1) What are signs of a chemical change? DO they always mean there is a chemical change? 2) What does this chemical equation tell you?
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Understanding Chemical Reactions Physical Science Chapter 10.1 Part 2
Our Story So Far • Think, discuss with partner, discuss with class • 1) What are signs of a chemical change? DO they always mean there is a chemical change? • 2) What does this chemical equation tell you? CH4+2O2 -> CO2+2H2O
Balancing Chemical Equations • The reaction combines hydrogen and oxygen molecules. For help -> http://misterguch.brinkster.net/eqnbalance.html Or http://phet.colorado.edu/en/simulation/balancing-chemical-equations
Help -> http://www.quia.com/rr/100887.html • Count the atoms to see if there are the same number of each type of atom on the reactant and product sides of the equation. • Since there is one more oxygen atom on the reactant side than there is on the product side, the reaction equation is not balanced.
A balanced chemical equation has the same number of each type of atom on the product side and the reactant side.
Balancing Chemical EquationsStep by Step • Write the unbalanced equation • NaOH + H2SO4 Na2SO4 + H2O • Draw boxes around all chemical formulas • NaOH + H2SO4 Na2SO4 + H2O • Make an element inventory
Balancing Chemical EquationsCONTINUED • Write numbers in front of the boxes until the inventory before and after balance • 2 NaOH + H2SO4 Na2SO4 + H2O
Balancing Chemical EquationsCONTINUED • You can change the coefficient on both sides -- but not the chemical formulas • 2 NaOH + H2SO4 Na2SO4 + 2 H2O
Your Turn • NaCl + BeF2 NaF + BeCl2
Your Turn • NaCl + BeF2 NaF + BeCl2
Your Turn • 2 NaCl + BeF2 NaF + BeCl2 • Keep going
Your Turn, continued • 2 NaCl + BeF2 2 NaF + BeCl2 • Done!
Warnings • Remember lowest common denominators - they can help • Coefficients are whole numbers • Don’t do this in your head – you are leaning a technique to apply to more complicated chemical equations.
Activity • Chemical Equation Worksheet • Due end of class