1. Chemical reactions

2. Which of the following are chemical reactions?

3. Signs of Chemical Reactions.
Energy is produced (heat or light)
Colour change happens
Gas forms
Precipitate forms

4. A chemical reaction is a process in which substances interact, causing the formation of new substances with new properties
Equations are used to describe chemical reactions
1 WORD EQUATIONS
Names of the chemicals are written out in full
II CHEMICAL EQUATIONS
Chemical formulas are used to represent the chemicals

5. Parts of the Equation Equations have 2 sides REACTANTS PRODUCTS
(get used up) (produced during the reaction)
An arrow tells the direction in which the chemical reaction is going. The arrow reads “yields, forms, or produces”
Substances to the left of the arrow are called reactants
Substances to the right of the arrow are called products
If more than 1 reactant is used we use a “+” sign between them
If more than 1 product is used we use a “+” sign between them

6. Energy: it’s role in reactions
Chemical reactions can either absorb or release energy
If absorbing energy: energy is placed on the reactant side
reactants + energy products
If releasing energy: energy is placed on the product side
reactants products + energy

7. Try This
A piece of zinc metal is placed in a solution of copper (II) sulfide, a fuzzy reddish-brown coating forms on the zinc, which is copper. The solution left is zinc sulfide. Energy is also released.
Word Equation:
Chemical Equation:

8. Ex: Iron and Sulfur
Iron and Sulfur are slightly heated; the result is iron (II) sulfide plus a lot of energy. More energy is released than absorbed so we write the word “energy” on the products side.
WORD EQUATION
CHEMICAL EQUATION

9. Chemical equations Provides more details!!
Gives chemical formulas and the state (solid, liquid, gas, aqueous) of the reactants and products
Ex: Green copper wire is mixed with silver chloride solution to produce silver metal precipitate and copper (II) chloride solution
WORD EQUATION
copper wire + silver chloride  silver metal + copper (II) chloride
CHEMICAL EQUATION
Copper (s) + AgCl (aq)  Ag (s) + CuCl2 (aq)

10. Li + AlCl3 —> LiCl + Al Try this
When Lithium metal is added to a solution of aluminum chloride, the products that formed was a solution of lithium chloride and aluminum metal.
Lithium metal + Aluminum chloride —> Lithium chloride + Aluminum
 Li +    AlCl3 —>    LiCl +    Al

11. C2H6 (g) + O2 (g) —> CO2 (g) + H2O (l)
Try this
When dicarbon hexahydride gas is lit with a spark in the presence of oxygen gas, a flame occurs and carbon dioxide gas and water forms.
Dicarbon hexahydride + Oxygen —> Carbon Dioxide + Water
C2H6 (g) +     O2 (g) —>  CO2 (g) +     H2O (l)

12. Assignment: Handout