1. Chemical Reactions and Law of Conservation of Mass

2. Chemical reactions are everywhere!
Chemical Reactions: the process by which the atoms of one or more substances are rearranged to form different substances.

3. Chemical Equations Reactants  Products Reactants: starting substances
Products: substances formed during the reaction
 means “yield” or “react to produce”

4. Law of Conservation of Mass
Mass is neither created nor destroyed during chemical or physical reactions.
Total mass of reactants =
Total mass of products
Antoine Lavoisier

5. The Law of conservation of mass states that matter cannot be created or destroyed in any chemical reaction
The atoms in the reactants are rearranged to form new compounds, but none of the atoms disappear, and no new atoms are formed. H O H O H H
Products
Reactants

6. Because of this law
When we write chemical equations, we have to make sure that they are balanced
In other words when we finish there has to be the same number of atoms on the left side as the right side

7. 4 main types of chemical reactions
Synthesis
Decomposition
Single Displacement
Double Displacement

8. Synthesis Reaction A new substance forms!!! A + B  AB
Ex. metal + oxygen  metal oxide
2 Mg (s) + O2 (g) MgO (s)

9. Decomposition Reaction
A compound is broken down (decomposed)
AB  A + B
Ex. salt  metal + nonmetal
2 NaCl (s)  2 Na (s) + Cl2 (g)

10. Single-Displacement Reaction
An element in a compound is replaced by another element
A + BC  B + AC or
A + BC  C + BA
Ex. metal + acid  hydrogen + salt
Zn (s) + 2 HCl (aq)  H2 (g) + ZnCl2 (aq)
Ex. metal + salt  metal + salt
Fe (s) + CuSO4 (aq)  Cu (s) + FeSO4 (aq)

11. Double-Displacement Reaction
Elements in two or more compounds all switch around
AB + CD  AD + CB
Ex. acid + base  salt + water
HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)

12. Can you Classify the following picture reactions?1 2 3 4

13. 4 Types of Reactions Synthesis Decomposition Single Displacement
Double
Displacement