2 Unit Seven: Changes in Matter Chapter 20 Chemical Reactions20.1 Chemical Changes20.2 Chemical Equations20.3 Conservation of Mass20.4 Using Equations as Recipes
3 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.
5 *Read text section 20.1 AFTER Investigation 20.1 20.1 Chemical ChangesKey Question:What is the evidence that a chemical change has occurred?*Read text section 20.1 AFTER Investigation 20.1
6 20.1 Chemical ChangesWe 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.
7 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)
14 20.3 Conservation of MassAntoine Laurent Lavoisier ( ), 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.
15 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
16 20.4 Using Equations as Recipes Recipe #1: Chocolate Cake Recipe1 cup flour1/2 cup cocoapowder1/2 cup butter1 tsp vanilla1 cup sugar1 teaspoon baking powder1/2 cup milk1 eggIn 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
17 20.4 Using Equations as Recipes Recipe #2: Water2 molecules of hydrogen gas1 molecule of oxygen gasCombine the molecules in a closed container.Add a spark of electricity.Makes two molecules of water.
18 20.4 Using Equations as Recipes Balanced equations show how mass and atoms are conserved.