Word Equations

• Millions of chemical reactions take place everyday

• The conversion of food you eat from food into chemical energy

• Plants undergoing photosynthesis to create their own energy

Word Equations

• Many reactions don’t involve life

• The energy your car obtains from the battery to start your car is a chemical reaction

• Metal rusting is a chemical reaction

Word Equations

• As you can see it is very important that you understand chemical reactions

Word Equations

• In a chemical reaction bonds are broken and reattached to form new chemical compounds

• When dealing with chemical reactions you must always consider the law of conservation of mass

Word Equations

• In a chemical reaction mass is neither lost nor gained

• Just as much product will be made as reactants that reacted

• Just think of a chemical reaction as a rearrangement

Chemical EquationsRusting

• Word Equation– Iron + Oxygen Iron (III) Oxide

• Chemical Equation– Fe + O2 Fe2O3

Chemical EquationsRusting

Fe (s) + O2 (g) Fe2O3(s)

• You can also indicate which physical state a substance is in– Solid (s)– Liquid (l)– Gaseous (g)– Aqueous Solution (aq)

Chemical Reactions

• Most chemical reactions will use a catalyst

• A catalyst is either an element or a compound which speeds up the chemical reaction– It is not used in the

reaction– It is written above the

arrow of the chemical reaction

Symbols Used in a Chemical Equation

1. +22 3. 4. (s)5. (g)6. (l)7. (aq)8. 9. 10.

1. Separates the reactants or products from each other

2. Separates the reactants and products

3. Reversible Reaction4. Solid State of Matter5. Gaseous State of Matter6. Liquid State of Matter7. Aqueous Solution8. Heat is supplied9. Heat is supplied10. Indicates which Catalyst has

been used

Heat

Pt

Balancing Chemical Equations

• Frame + Wheel + Handlebar + Pedal = Bicycle• Will this make a bicycle?• No• Why not?• A bicycle has 2 wheels and 2 pedals• So the correct formula for a bicycle is • Frame + 2 Wheels + Handlebar + 2 Pedals =

Bicycle• This is called a Balanced Equation

Balancing Chemical Equations

• A balanced equation occurs when all reactants equal all the products

H20 + CO2 C6H1206 + O2

Rules for Balancing Equations1. Determine the correct

formula for all the reactants and products in the reaction

2. Write the formulas for the reactants on the left and formulas for the products on the right

3. Count the number of atoms of each element in the reactants and products

4. Balance the elements one at a time by using coefficients, when no coefficient is written assume it to be 1

5. Double check everything to be sure

6. Make sure you have the lowest number combination possible