CHAPTER 20 CHEMICAL REACTIONS

20.3 Conservation of Mass Antoine Laurent __________ ( ), established an important principal based on his experiments with chemical reactions. The total mass of the ________ of a reaction is equal to the total mass of the __________. This is known as the law of ___________ of mass.

CONSERVATION OF MASS Total MASS of PRODUCTS EQUALS Total MASS of REACTANTS – Must MEASURE in a _________ SYSTEM Antoine Lavoisier

CONSERVATION OF MASS Mass of WOOD and AIR before burning a fire EQUALS Mass of ASH and GASES after burning a fire

COOKING WITH CHEMISTRY CHEMICAL EQUATIONS ARE LIKE RECIPES They tell you QUANTITIES of INGREDIENTS and Quantities of PRODUCTS

CHEMICAL EQUATIONS NUMBER of REACTANT MOLECULES needed to MAKE a CERTAIN NUMBER of PRODUCT MOLECULES 2Na + Cl > 2NaCl

BALANCED EQUATIONS Correct RATIOS of Molecules are shown as COEFFICIENTS in BALANCED EQUATIONS 2H 2 + O > 2H 2 O

UNBALANCED REACTIONS REACTANTS ARE NOT ALWAYS PRESENT IN THE EXACT RATIOS NEEDED. SO WHAT HAPPENS ?

_______ REACTANT The reactant molecule which is used up _____ _______ the AMOUNT of PRODUCT formed UNBALANCED UNBALANCED REACTIONS REACTIONS

__________ REACTANT The reactant molecule which is _____ completely used up. Some will be _____ _____ after reaction is complete. UNBALANCED UNBALANCED REACTIONS REACTIONS

YIELDS REACTIONS DON’T ALWAYS TURN OUT AS PLANNED HOW MUCH PRODUCT IS REALLY FORMED ?

_________ YIELD – The amount of Product ________ from the balanced equation _________ YIELD – The amount of Product _________ formed

PERCENT YIELD RATIO of Actual Yield to Predicted Yield %YIELD = Actual Yield x 100% Predicted Yield

PERCENT YIELD IF we expect 100g. of product from chemical equation, BUT we only get 85g. of product, THEN % YIELD = (85g./100g.)x100% = 85%

20.4 Using Equations as Recipes Recipe #1: Chocolate Cake Recipe 1 cup flour 1/2 cup cocoa powder 1/2 cup butter 1 tsp vanilla 1 cup sugar 1 teaspoon baking powder 1/2 cup milk 1 egg In a bowl, combine flour, sugar, cocoa powder, and baking power. Add butter, milk, vanilla, and egg. Mix until smooth. Bake in a 350°F oven for 35 minutes. Makes 8 servings

20.4 Using Equations as Recipes Recipe #2: Water 2 molecules of hydrogen gas 1 molecule of oxygen gas Combine the molecules in a closed container. Add a spark of electricity. Makes two molecules of water.

20.4 Using Equations as Recipes Balanced equations show how mass and atoms are conserved.

20.4 Using Equations as Recipes

20.4 Using Equations Key Question: How can you predict the amount of product in a reaction? *Read text section 20.4 BEFORE Investigation 20.4