Unit: Chemical Reactions Day 1 - Notes Unit: Chemical Reactions Diatomic elements, Writing formula equations from word equations Upper left: Thermite reaction, Fe2O3 + Al => 2Fe +2Al2O3 + HEAT!!! http://en.wikipedia.org/wiki/Thermite Upper right: potassium in water, K + H2O => KOH + H2 + HEAT Bottom right: potassium chlorate and sugar, C12H22O11 + 8KClO3 => 12CO2 + 11H2O + 8KCl + HEAT!!! http://lecturedemos.chem.umass.edu/chemReactions5_5.html Bottom left: magnesium reacting with oxygen, Mg + O2 => MgO

After today you will be able to… Name the diatomic elements Write formula equations given the word equation for a chemical reaction heat Pt

A chemical equation represents a chemical reaction. Reactants  Products “Yield” Reactants and products are separated from each other with a plus (+) sign.

Common forms of chemical reactions… A + B  C A  B + C A + B  C + D

Chemical equations can be written as word equations or formula equations. Formula equations can be balanced or unbalanced.

Word Equation: Iron + Oxygen  Iron (III) Oxide Formula Equation: 4Fe(s) + 3O2(g)  2Fe2O3(s) Balanced!

Symbols in Chemical Equations Meaning (s) Solid (l) Liquid (g) Gas (aq) Aqueous (dissolved in H2O)  Reversible reaction  or  Heat is added  Catalyst is added (A substance that speeds up a reaction.) heat Pt

To change word equations into formula equations follow the flow chart…

ELEMENT? Monatomic Diatomic Is the substance an… ELEMENT? Monatomic Diatomic Just write the symbol Example: “Sodium”=Na Br2 I2 N2 Cl2 H2 O2 F2 Have the subscript “2” Examples: “Bromine”=Br2 “Hydrogen” = H2

Is the substance a… COMPOUND? CaCl2 N2O4 Ionic Molecular (M +nM) (nM +nM) Balance charges!!! Example: “calcium chloride” Ca+2 Cl-1 Cl-1 Prefixes for subscripts Examples: “dinitrogen tetraoxide” CaCl2 N2O4

Let’s try some examples! 

Helpful tip: Keep all substances and + signs in Examples: Convert into formula equations… 1. sodium chloride + fluorine  sodium fluoride + chlorine 2. aluminum + sulfur  aluminum sulfide Helpful tip: Keep all substances and + signs in line with each other! Na+1 Cl-1 Na+1 F-1 NaCl + F2  NaF + Cl2 Al+3 S-2 Al + S  Al2S3

+ Mg3(AsO4)2 ZnS  Zn3(AsO4)2 + MgS 3. zinc + magnesium  zinc + magnesium Zn+2 S-2 Mg+2 (AsO4)-3 Zn+2 (AsO4)-3 Mg+2 S-2 sulfide arsenate arsenate sulfide + Mg3(AsO4)2 ZnS  Zn3(AsO4)2 + MgS

Do now: Complete “Exit Ticket” Then: Begin WS 1 (Homework)