Integrated Science Unit 7, Chapter 20

Unit Seven: Changes in Matter Chapter 20 Chemical Reactions 20.1 Chemical Changes 20.2 Chemical Equations 20.3 Conservation of Mass 20.4 Using Equations as Recipes

Chapter 20 Learning Goals Distinguish between physical and chemical changes in matter using examples from everyday life. Write and balance chemical equations. Investigate and identify the law of conservation of mass. Use chemical equations to predict the amount of product that will be produced in a reaction. Design an experiment to prove conservation of mass. Identify the mathematical relationship between the mass in grams of reactants and products, the coefficients in a balanced equation, and the formula masses of the reactants and products. Identify economic and environmental reasons for recycling tires.

Chapter 20 Vocabulary Terms balance chemical change chemical equation chemical reaction coefficient conservation of mass excess reactant hydrochloric acid product limiting reactant reactant percent yield physical change

*Read text section 20.1 AFTER Investigation 20.1 20.1 Chemical Changes Key Question: What is the evidence that a chemical change has occurred? *Read text section 20.1 AFTER Investigation 20.1

20.1 Chemical Changes We can classify changes in matter as either chemical changes or physical changes. The process of digestion involves both physical and chemical changes to the food.

20.1 Chemical Changes Evidence of chemical change: bubbling (formation of gas) turning cloudy (formation of a new solid) temperature change (heat or light released) color change (formation of a new solid)

20.2 Chemical Equations Key Question: How do you balance chemical equations? *Read text section 20.2 AFTER Investigation 20.2

20.2 Chemical Equations Numbers and types of atoms must balance

20.3 Conservation of Mass Antoine Laurent Lavoisier (1743-94), established an important principal based on his experiments with chemical reactions. The total mass of the products of a reaction is equal to the total mass of the reactants. This is known as the law of conservation of mass.

20.3 Conservation of Mass Key Question: How can you prove that mass is conserved in a reaction? *Read text section 20.3 BEFORE Investigation 20.3

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