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What is a polyatomic ion?
Agenda for Thursday Jan 20th 1.Polyatomic bonding practice2.Bonding review
How do we know a chemical reaction has occurred?
Agenda for Friday Jan 21st
1.Chemical reactions intro2.Movie
Chemical Reactions
• New substances are formed
• Four signs of a chemical reaction– Gas produced– Color Change– Change in energy (Heat/Cold)– Light
2Na + Cl2 2NaCl
reactants products
Reactant: substance changedProduct: substance formed
Coefficient: # showing how many molecules are involved in rxn.
Coefficient
Chemical equation: use chemical formulas to show rxn.
Important Symbols
Symbol Meaning
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 24th 1.Baggie Lab2.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 color4. changes odor5. produces flame6. makes noise7. produces a solid (precipitate)
What are some factors that effect chemical reactions?
Agenda for Tuesday Jan 25th 1.Types of reactions2.Concept Review
Diatomic Molecules
• Molecule made up of only 2 atoms
• Memorize these:
H2 O2 F2 Br2 I2 N2 Cl2
**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 + Cl2 → 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
• Example: decomposition of water2H2O → 2H2 + O2
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 aluminum3CuCl2 + 2Al → 2AlCl3 + 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. AgNO3 + NaCl NaNO3 + AgCl
*Take place in solutions*Often form precipitates
Combustion
• Substance combines with oxygen, releases energy as light and/or heat
• Ex. Burning propane: C3H8 + O2 CO2 + H2O
Reaction Checklist
1) Is O2 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 equation1. Remember rules for writing formulas
3. Check for diatomic molecules
Example
Na3N ______________
1.Identify the type of reactionDecomposition
Na + N 2
Example
AlPO4 + Cs _____________________
1.Single Replacement
What is exothermic and endothermic?
Agenda for Wednesday Jan 26th 1.Mg/HCl Lab
What are the 5 types of chemical reactions?
Agenda for Thursday Jan 27th 1.Finish yesterdays lab2.Conservation of mass
1. Lab
3.Practice with reactions types
Lab Wrap – up
Mg(s) + 2 HCl(aq) H2(g) + MgCl2(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 + O2 2 MgO
2CH4 + 4 O2 2 CO2 + 4 H2O
3 CuCl2 + 2 Al 2 AlCl3 + 3 Cu
Pb(NO3)2 + K2CrO4 PbCrO4 + 2KNO3
2HgO 2Hg + O2
What does the conservation of mass state?
Agenda for Friday Jan 28th 1.Quiz2.Video clips fireworks/exposives3.Other cool stuff