what is a polyatomic ion? agenda for thursday jan 20 th 1.polyatomic bonding practice 2.bonding...

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