Chemical Reactions

Chemical Reactions 7.1 Chemical reactions alter arrangements of atoms. CHAPTER NEW CHAPTER Chemical Reactions the BIG idea Chemical reactions form new substances by breaking and making chemical bonds. 7.1 Chemical reactions alter arrangements of atoms. 7.2 The masses of reactants and products are equal. 7.3 Chemical reactions involve energy changes. 7.4 Life and industry depend on chemical reactions. CHAPTER OUTLINE 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. Cause chemical changes Make new substances Draw a picture ?

Four Square Vocabulary Chemical reaction Definition Characteristics Example Nonexample

Four Square Vocabulary Chemical reaction Definition The process by which chemical changes occur. Characteristics Atoms are rearranged Produces a new substance Bonds are broken New bonds form between different atoms Rust form on iron Wood burns to form smoke and ash Example Liquid water changes to water vapor during boiling Physical change Non-example

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? Physical change 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 Temperature Change 2. Formation of a Gas Burning (Foaming/Fizzing/ Bubbling)

Evidence of Chemical Reactions Odor change 4. Corroding Acids 5. Formation of a Precipitate

Four Square Vocabulary Precipitate A solid substance that forms as a result of a reaction between chemicals in two liquids Definition Different physical state from the reactants Characteristics Solid Seashells – formed when sea creature releases a liquid that reacts with seawater Example Non-example Liquid Gas

Evidence of Chemical Reactions 6. Color Change Rusting metal (iron + oxygen = rust) Explosions (fireworks) Verdigris- greened statutes (copper + sulfur)

Evidence of Chemical Reactions 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 Color change Formation of a gas Temperature change Irreversible New Substance

Any type of burning

Rusting Metal = iron + oxygen

Verdigris: copper + sulfur

Fireworks

Leaves changing color

Plant photosynthesis

Cheese production

Soured milk

Eggs rotting

Baking a cake

Mixing liquids: colors change

Foaming (gas formation) Ex: antacid in water

Corrosion due to acids (bubbling or fizzing)

P. Physical Change or C. Chemical Change? Painting a statue Chopping wood Crushing sugar crystals Dissolving salt Boiling water Exploding firecrackers Mixing baking soda & vinegar

P. Physical Change or 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 CH4 + O2 → Reactants Substances present at the beginning of a chemical reaction Methane + Oxygen Left side of the chemical equation

Reactants and Products Substance(s) formed by a chemical reaction Carbon dioxide + water Right side of the chemical equation →CO2 + H2O

Four Square Vocabulary Reactant A substance that is present at the beginning of a chemical reaction Definition Changed into a new substance Characteristics CH4 + O2 CO2 + H2O

Four Square Vocabulary Product A substance formed by a chemical reaction. Definition New bonds formed from the reactants Rearrangement of atoms Characteristics Example CO2 + H2O Non-Example CH4 + O2

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 Particles collide Occur at different rates Concentration Surface Area Temperature Catalysts Inhibitor Draw a picture? Quick reaction for the match to light up 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