1. Reaction Types

2.  A process that changes one or more substances into one or more new substances. O -2 H +1 O -2 H +1 2H 2 + O 2 2H 2 O

3. Five observations that indicate a chemical reaction has occurred are:  a)permanent color change  b)formation of a precipitate  c) gas is produced  d)an endergonic or exergonic reaction e)give off light

4. Molecules must collide in order to react. O -2 H +1 O -2 H +1

5.  A chemical equation is a shorthand method used by scientists to show the changes that take place in a chemical reaction. 2H 2 + O 2 2H 2 O

6. A chemical reaction can be shown by writing a word equation. For example, Carbon plus oxygen yields carbon dioxide More often symbols and chemical formulas are used in place of words. This is called a formula equation. C + O 2  CO 2

9. . In a chemical equation reactants are written to the left of the arrow and products are written to the right of the arrow ( reactants  products). 2H 2 + O 2 2H 2 O

10. A synthesis reaction is a reaction in which two or more substances combine to form only one product. General equation: A + B ------> AB Ex. Mg + S ------> MgS

11. A decomposition reaction is a reaction in which a compound breaks down into two or more products. General equation: AX ------> A + X Ex. BaS ------> Ba + S

12.  A single replacement reaction takes place when one element replaces another element in a compound.  Zn + CuCl 2 ZnCl 2 + Cu  This forms a new compound and leaves the less active element by itself. If the free element is less active, then no reaction occurs.  Cu + ZnCl 2

13. When the free element is a metal: General equation: AX + B ------> BX + A [only if B is stronger than A] Ex. ZnS + Mg -------> MgS + Zn

14. Most Reactive Least Reactive

15. A double replacement reaction takes place when the compounds in a reaction exchange ions. General equation: XY + AB -------> XB + AY Ex. BaS + CaO ------> BaO + CaS