1 FLASHBACK! Chemical Reactions Types of Chemical Equations Balancing Chemical Equations Reaction Rates

 Awareness of basic chemistry can save your life!  Example: mixing certain cleaning solutions can produce a poisonous gas  Ammonia (Windex) + Bleach (Clorox) Chloroamine (a poisonous gas)  Chemistry is alive in our everyday life:  Ice Packs, Hot Packs, Air Bags in Cars, Foods Why should we care about chemical combinations? →

Compounds are groups of elements chemically bonded together 2 types we’ve studied: IONIC – bonding where electrons are gained or lost COVALENT – bonding where electrons are shared

A reaction that releases energy and gives off heat/light/sound resulting in a raising of temperature “energy” will be with the products side of a chemical equations Examples: glow sticks, fire, lycopodium powder

A reaction that ABSORBES energy resulting in LOWERING of temperature. “energy” will be with the REACTANTS side of a chemical equations Examples: ANTACID & WATER, PHOTOSYNTHESIS

Changes in PHYSICAL properties 1. Melting 2. Boiling 3. Condensation 4. Evaporation 5. Sublimation 6. Change in Size or Shape NO change occurs in the IDENTITY of the substance(s) Examples: Ice, rain, and STEAM are all WATER

Atoms in the REACTANTS are REARRAGED to form one or more DIFFERENT substances OLD chemical BONDS are BROKEN and NEW chemical BONDS are FORMED Changes DO occur in the identity of the compounds since NEW compounds are formed Examples:  Fe and O 2 form RUST (Fe 2 O 3 )  Ag and S form TARNISH (Ag 2 S)

1. New substance produced 2. Production of a gas 3. Change in color 4. Change in smell 5. Change in heat or light

Classify each of the following as a PHYSICAL CHANGE (P) or a CHEMICAL CHANGE (C) A. ____ a burning candle B. ____ steam coming up from boiling H2O C. ____ toasting a marshmallow D. ____ cutting a pizza E. ____ polishing silver

Classify each of the following as a PHYSICAL CHANGE (P) or a CHEMICAL CHANGE (C) A. _C_ a burning candle B. _P_ steam coming up from boiling H2O C. _C _ toasting a marshmallow D. _ P cutting a pizza E. _ C _ polishing silver

A process in which AT LEAST ONE NEW SUBSTANCE IS PRODUCED AS A RESULT OF A CHEMICAL CHANGE. 11

REACTANTS PRODUCTS Draw the contents of these two boxes on your paper

A. Use the box drawing to determine, how does the equation indicate a change in the identity of the reacting substances? B. Does the equation follow the Law of Conservation of Matter? How can you tell?

A. Use the box drawing to determine, how does an equation indicate a change in the identity of the reacting substances? The formulas of the reactants are different than the formulas of the products. B. Does the equation follow the Law of Conservation of Matter? How can you tell? Yes, there are the same number and kinds of symbols (atoms) on both sides of the chemical equation.

Chemical equations give a “BEFORE & AFTER” picture of a chemical reaction ReactantsProducts MgO + C CO + Mg *magnesium oxide TO FORM *carbon monoxide REACTS with carbon and magnesium 15 →

12 oz of dough, 4 oz mushrooms, 12 slices pepperoni, 8 oz cheese and 5 oz tomato sauce are used to make a pizza. A. How would you write the recipe above as an equation?

12 oz of dough, 4 oz mushrooms, 12 slices pepperoni, 8 oz cheese and 5 oz tomato sauce are used to make a pizza. A. How would you write the recipe as an equation? 12 oz dough + 4 oz mshrm + 12 pep + 8 oz chse 1 pizza + 5 oz tom sauce

4NH 3 + 5O 2 → 4NO + 6H 2 O ________ molecules of NH 3 REACT with ________ molecules O 2 TO PRODUCE ________ molecules of NO and ________ molecules of H 2 O FOUR FIVE FOURSIX

SAME numbers of EACH TYPE OF ATOM on each side of the equation Al + S → Al 2 S 3 2Al + 3S → Al 2 S 3 When balancing an equation, _______change subscripts; _________ change ______________ Not Balanced Balanced NEVER COEFFICIENTSALWAYS

H 2 + Cl 2 → 2HCl Total Atoms = Total Atoms H = 2, Cl = 2 H = 2, Cl = 2 Total Mass = Total Mass 2 (1.0) + 2 (35.5)2 ( ) 73.0 amu = 73.0 amu →++

In any ordinary chemical reaction, MATTER IS NOT CREATED or DESTROYED

Add Coefficients IN FRONT of compounds to BALANCE the equation 4NH 3 + 5O 2 4NO + 6H 2 O N = &N = H = &H = O = &O =

Fe 3 O 4 + H 2 Fe + H 2 O Fe:Fe 3 O 4 + H 2 3Fe + H 2 O O:Fe 3 O 4 + H 2 3Fe + 4H 2 O H: Fe 3 O 4 + 4H 2 3Fe + 4H 2 O

Fe 3 O 4 + 4H 2 3Fe + 4H 2 O A. Number of H atoms in the reactants? B. Number of O atoms in the reactants? C. Number of Fe atoms in the reactants?

Fe 3 O 4 + 4H 2 3Fe + 4H 2 O A. Number of H atoms in the reactants? 8 B. Number of O atoms in the reactants? 4 C. Number of Fe atoms in the reactants? 3

6CO 2 + 6H 2 O + sunlight C 6 H 12 O 6 + 6O 2 A. Number of carbon atoms in the reactants? B. Number of oxygen atoms in the reactants? C. Number of hydrogen atoms in the reactants? D. Is this a endo or exothermic reaction? What important biological process does this chemical equation represent?

6CO 2 + 6H 2 O + sunlight C 6 H 12 O 6 + 6O 2 A. # of carbon atoms in the reactants? 6 B. # of oxygen atoms in the reactants? 18 C. # of hydrogen atoms in the reactants? 12 D. Is this a endo or exothermic reaction? What important biological process does this chemical equation represent? Endothermic Reaction; Photosynthesis

Balance each equation. SHOW YOUR WORK! A. Mg + N 2 Mg 3 N 2 B. Al + Cl 2 AlCl 3 C. Fe 2 O 3 + C Fe + CO 2 D. Al + FeO Fe + Al 2 O 3

Balance each equation. SHOW YOUR WORK! A. Mg + N 2 Mg 3 N 2 B. Al + Cl 2 AlCl 3 C. Fe 2 O 3 + C Fe + CO 2 D. Al + FeO Fe + Al 2 O

1. Synthesis  Getting Together  A + B → AB  ___Fe + ___O 2 → ___Fe 2 O 3 Iron reacts with Oxygen to produce rust 2 34

2. Decomposition  Breaking Apart  AB → A + B  ___H 2 O 2 → ___H 2 O + O 2 + energy Hydrogen Peroxide reacts with Oxygen to produce water & oxygen & energy 2 2

3. Single Replacement Reaction  One Exchange  AB + C → A + BC or A + BC → AB + C  Ag + H 2 S → AgS + H 2 Silver Tarnishing

4. Double Replacement Reaction  Two Exchanges  AB + CD → AC + BD  HCl + NaOH → NaCl + H 2 O Acid + Base → Salt + Water  CH 3 COOH + NaHCO 3 → CH 3 COON 2 + H 2 O + CO 2 Vinegar + Baking Soda → Sodium Acetate Salt + Water + Carbon Dioxide (Neutralization)

Determine which type of chemical reaction is shown: A. CuCl 2 + H 2 S → CuS + 2HCl B. 2H 2 O → 2H 2 + O 2 C. MgO + Fe → FeO 3 + Mg D. P 4 + 5O 2 → P 4 O 10 DR D SR S

E. Ag + H 2 S → AgS + H 2 F. Fe 3 O 4 + 4H 2 → 3Fe + 4H 2 O G. 3Mg + N 2 → Mg 3 N 2 H. 3Al + 3Cl 2 → 2AlCl 3 I. HCl + NaOH → NaCl + H 2 O J. 2Fe 2 O 3 + 3C → 4Fe + 3CO 2 K. 2Al + 3FeO → 3Fe + Al 2 O 3 L. 2Fe 2 O 3 → 4Fe + 3O 2 SR S S DR SR D

“Reaction Rates” refers to HOW FAST A REACTION OCCURS

Factors that Influence Reaction Rates 1. Temperature  Examples: o Glow sticks in HOT water glow brighter than one in cold water o Antacid dissolves faster in HOT water than cold water

Factors that Influence Reaction Rates 2. Surface Area  Refers to how much of the outside of a substance is exposed  The greater surface area, the faster the reaction  Examples: o Lycopodium Powder o Headache medicine reacts faster in powder form than solid form (ex. Goodie Powder versus Tylenol Pill)

Factors that Influence Reaction Rates 3. Concentration  Refers to how much of a substance there is  The greater concentration of a reactant, the faster the reaction  Example: o Vinegar & Baking Soda in Beaker – more vinegar produces a faster reaction

Factors that Influence Reaction Rates 4. Presence of a Catalyst  Refers to a substance that speeds up a reaction but is NOT used up by the reaction  The catalyst can be recovered unchanged, and re- used indefinitely  Examples: o Yeast in our “chemiluminescent elephant’s toothpaste” reaction o Enzymes found in animals that speed up digestion

Factors that Influence Reaction Rates 5. Presence of an Inhibitor  Refers to something that slows down or stops a chemical reaction  Examples: o Why do we cover our left over foods? o Why do we even put food in the fridge? o Why do we use food preservatives like salts?

List 4 ways to make a reaction occur faster (increase the speed):

List 4 ways to make a reaction occur slower (decrease the speed):

See Study Guide From Chapter 7 Test