What is a polyatomic ion? Agenda for Thursday Jan 20 th 1.Polyatomic bonding practice 2.Bonding review

How do we know a chemical reaction has occurred? Agenda for Friday Jan 21 st 1.Chemical reactions intro 2.Movie

Chemical Reactions New substances are formed Four signs of a chemical reaction – Gas produced – Color Change – Change in energy (Heat/Cold) – Light

2Na + Cl 2  2NaCl reactants products Reactant: substance changed Product: substance formed Coefficient: # showing how many molecules are involved in rxn. Coefficient Chemical equation: use chemical formulas to show rxn.

Important Symbols SymbolMeaning  Reacts to form (yields) +Plus (and) ∆heat (s)solid (l)liquid (g)gas (aq)Aqueous; dissolved in water

Energy and reactions All reactions need some type of energy to start – Spark, heat, – Energy needed to start a reaction is called activation energy

Exothermic and Endothermic Exothermic – energy is released – Heat is given off Endothermic – requires energy – Cold

Factors that effect Chemical Changes Temperature Warm = Faster Cold = Slower Nature of the reactants Size and shape of molecules Large is slower (heat = energy = motion) Concentration Gasses at high pressures

Factors Cont. Surface Area – More = faster – Less = slower

Factors Catalysts – Added to speed up or slow down a reaction. – Not used in the reaction Not a reactant or a product Enzymes are biological catalysts

Enzymes as Catalysts

What are 4 clues a chemical reaction is taking place? Agenda For Monday Jan 24 th 1.Baggie Lab 2.Types of Chemical Reactions

Signs of a Chemical reaction 1. Produces a gas – bubbles 2. Change in energy (heat = exothermic or cold = endothermic) 3. changes color 4. changes odor 5. produces flame 6. makes noise 7. produces a solid (precipitate)

What are some factors that effect chemical reactions? Agenda for Tuesday Jan 25 th 1.Types of reactions 2.Concept Review

Diatomic Molecules Molecule made up of only 2 atoms Memorize these: H 2 O 2 F 2 Br 2 I 2 N 2 Cl 2 **These molecules never exist alone, they are always in pairs.

5 Types of Reactions Synthesis Decomposition Single replacement Double replacement Combustion

Synthesis making a new compound out of 2 substances Synthesis reactions have the following general form: A + B → AB Example:2Na + Cl 2 → 2NaCl **Always form one product

Decomposition Substance is broken down into 2 or more substances Most need energy (like heat) to happen Decomposition reactions have the general form: AB → A + B AB → A + B Example: decomposition of water 2H 2 O → 2H 2 + O 2

Single Replacement One element replaces another element Single-displacement reactions have the general form: AX + B → BX + A Example: single-displacement between copper(II) chloride and aluminum 3CuCl 2 + 2Al → 2AlCl 3 + 3Cu *Not all SR reactions “work”

Double Replacement Elements from 2 different compounds replace each other Double-displacement reactions have the following general form: AX + BY → AY + BX Ex. AgNO 3 + NaCl  NaNO 3 + AgCl *Take place in solutions *Often form precipitates

Combustion Substance combines with oxygen, releases energy as light and/or heat Ex. Burning propane: C 3 H 8 + O 2  CO 2 + H 2 O

Reaction Checklist 1) Is O 2 a reactant? (combustion) 2) One product? (synthesis) 3) One reactant? (decomposition) 4) Is an element being replaced? (single) 5) 2 switches? (double)

Predicting Products 1.Identify the type of reaction 2.Write products on right side of equation 1.Remember rules for writing formulas 3.Check for diatomic molecules

Example Na 3 N  ______________ 1.Identify the type of reaction Decomposition Na + N 2

Example AlPO 4 + Cs  _____________________ 1.Single Replacement

What is exothermic and endothermic? Agenda for Wednesday Jan 26 th 1.Mg/HCl Lab

What are the 5 types of chemical reactions? Agenda for Thursday Jan 27 th 1.Finish yesterdays lab 2.Conservation of mass 1.Lab 3.Practice with reactions types

Lab Wrap – up Mg (s) + 2 HCl (aq)  H 2(g) + MgCl 2(aq)

Conservation of mass In a closed system, mass is not created or destroyed – Constant Amount of the reactants = amount of products

Practice predicting types of reactions 2 Mg + O 2 2 MgO 2CH O 2 2 CO H 2 O 3 CuCl Al 2 AlCl Cu Pb(NO 3 ) 2 + K2CrO 4 PbCrO 4 + 2KNO 3 2HgO 2Hg + O 2

What does the conservation of mass state? Agenda for Friday Jan 28 th 1.Quiz 2.Video clips fireworks/exposives 3.Other cool stuff