Chemical Reactions

NEW CHAPTER

Chemical Reactions

CHAPTER

thethe BIGBIG ideaidea

Chemical reactions form new substances by breaking and making chemical bonds.

Chemical reactions alter arrangements of atoms.

The masses of reactants and products are equal.

Chemical reactions involve energy changes.

Life and industry depend on chemical reactions.

CHAPTER OUTLINE

7.17.1

7.27.2

7.37.3

7.47.4

CHAPTER RESOURCES

GOAL

• To distinguish between physical and chemical changes

Chemical reactions alter arrangement of atoms

• Atoms of one element differ from atoms of all other elements

• Chemical bonds hold compounds together• Chemical bonds may be __________ or

____________.

Chemical reactions alter arrangements of atoms.

• About chemical changes and how they occur

• About three types of chemical reactions

• How the rate of a chemical reaction can be changed

Atoms interact in chemical reactions.

Physical Changes• A change in state

of a substance

• Same substance

• Substance may have different properties

• Draw a picture?

Atoms interact in chemical reactions.

Chemical reactions

• Cause chemical changes

• Make new substances

Draw a picture ?

Four Square Vocabulary

Four Square Vocabulary

Chemical Changes

• Changing the substance into a new one by changing atoms

• Bonds are broken • New bonds are

formed

Atoms interact in chemical reactions.

What kind of change occurs when a substance changes state?

a. Physical change

b.Chemical change

EXPLORE: Chemical Changes

How can you identify a chemical change?

EXPLORE: Chemical Changes

• What did you see on the nail?

Copper

• Where do you think it came from?

The copper came from the pennies.

• Did a new substance form?

Yes

• What evidence supports your conclusion?

A color change

Evidence of Chemical Reactions

Chemical Indicators

1. Temperature Change

2. Formation of a Gas

Burning

(Foaming/Fizzing/ Bubbling)

Evidence of Chemical Reactions

3. Odor change

4. Corroding Acids

5. Formation of a Precipitate

Four Square Vocabulary

Evidence of Chemical Reactions

6. Color Change• Rusting metal

(iron + oxygen = rust)

• Explosions (fireworks)

• Verdigris- greened statutes

(copper + sulfur)

Evidence of Chemical Reactions

7. Cooking & some food production (cake baking, cheese production)

8. Chemical processes in nature (photosynthesis)

Evidence of Chemical Reactions

9. Irreversible

(New Substance is formed)

Evidence of Chemical Reactions

• Changing Steel Wool

List the evidence/indicators of a

chemical reaction.

Changing Steel Wool

P. Physical Changeor

C. Chemical Change?

• Painting a statue

• Chopping wood

• Crushing sugar crystals

• Dissolving salt

• Boiling water

• Exploding firecrackers

• Mixing baking soda & vinegar

P. Physical Changeor

C. Chemical Change?

• Rotting eggs

• Crumpling wax paper

• Slicing cucumber

• Fizzing antacid in water

• Lighting a match

• Zipping a coat up

• Rusting bike chains

Reactants and Products

Reactants• Substances present at

the beginning of a chemical reaction

• Methane + Oxygen• Left side of the

chemical equation

CH4 + O2 →

Reactants and Products

Products• Substance(s) formed

by a chemical reaction• Carbon dioxide + water

• Right side of the chemical equation

→CO2 + H2O

Four Square Vocabulary

Four Square Vocabulary

Reactants and Products

• What products are formed when water is broken down during a chemical change?

• A. hydrogen and carbon

• B. hydrogen and oxygen

• C. oxygen and oxygen

• D. hydrogen and hydrogen

Rates of Chemical Reactions

Chemical Reactions• Particles collide• Occur at different

rates• Concentration

• Surface Area

• Temperature

• Catalysts

• Inhibitor

Draw a picture?

Takes months for the nail to rust

Rates of Chemical Reactions

Concentration• Measures the number

of particles present in a certain volume.

• INCREASES the rate of chemical reaction Which atoms have a

higher concentration?

Rates of Chemical Reactions

Surface area• Breaking a large piece

of material into smaller parts

• More surfaces are exposed

• Amount of material does not change

• INCREASES the rate of chemical reaction

Rates of Chemical Reactions

Temperature• Making particles

move faster• More

collisions/greater force

• Add energy to the reactant

• INCREASES the rate of chemical reaction

Rates of Chemical Reactions

Catalysts• A substance added • Not consumed• Can be organic,

synthetic or metal

INCREASES the rate of reaction