Unit 7, Chapter 20 Integrated Science
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.
excess reactant hydrochloric acid product limiting reactant reactant percent yield physical change Chapter 20 Vocabulary Terms • balance • chemical change • chemical equation • chemical reaction • coefficient • conservation of mass
Key Question: What is the evidence that a chemical change has occurred? 20.1 Chemical Changes *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)
Key Question: How do you balance chemical equations? 20.2 Chemical Equations *Read text section 20.2 AFTER Investigation 20.2
20.2 Chemical Equations • Numbers and types of atoms must balance
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? 20.3 Conservation of Mass *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.
Key Question: How can you predict the amount of product in a reaction? 20.4 Using Equations *Read text section 20.4 BEFORE Investigation 20.4