Unit 7, Chapter 20

Integrated Science

Unit Seven: Changes in Matter

20.1 Chemical Changes

20.2 Chemical Equations

20.3 Conservation of Mass

20.4 Using Equations as Recipes

Chapter 20 Chemical Reactions

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 excess reactant

hydrochloric acid product

limiting reactant

reactant

percent yield

physical change

balance

chemical change

chemical equation

chemical reaction

coefficient

conservation of mass

20.1 Chemical ChangesKey Question: What is the evidence that a chemical change has

occurred?

*Read text section 20.1 AFTER Investigation

20.1

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.

20.1 Chemical ChangesEvidence 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 EquationsKey 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 MassKey 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 RecipesRecipe #1: Chocolate Cake Recipe

1 cup flour1/2 cup cocoa

powder1/2 cup butter1 tsp vanilla1 cup sugar

1 teaspoon baking powder1/2 cup milk

1 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

20.4 Using Equations as RecipesRecipe #2: Water

2 molecules of hydrogen gas1 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 EquationsKey Question: How can you predict the amount of product in a

reaction?

*Read text section 20.4 BEFORE Investigation 20.4