1. Classifying Chemical Reactions Types
Synthesis Reaction
Decomposition Reactions
Single-Replacement Reactions
Double-replacement Reactions
Combustion Reactions

2. A Synthesis Reaction
When iron rusts, iron metal and oxygen gas combine to form one new substance, iron(III) oxide.
The balanced equation for this synthesis reaction shows that there is more than one reactant but only one product.

3. Synthesis Reactions
A chemical reaction in which two or more substances react to yield a single product.
A + B  AB

4. Zinc and Iodide synthesis reaction

5. Decomposition Reactions
A chemical reaction that occurs when a single compound breaks down into two or more elements or new compounds.
AB  A + B

6. A Decomposition Reaction
When ammonium nitrate is heated to a high temperature, it explosively breaks down into dinitrogen monoxide and water.
The decomposition reaction taking place is represented by a balanced equation that shows one reactant and more than one product.

7. Decomposition of Nitrogen Triiodide

8. Decomposition of Nitrogen Triiodide
Molecules store energy (chemical potential energy) in the bonds that hold them together. When the bonds are broken, energy is released.
2 NI3(s) N2(g) I2(g)

9. YouTube - Elementary Productions: Ammonium Dichromate

10. Single-replacement Reactions
A chemical reaction that occurs when the atoms of one element replace the atoms of another element in a compound.
A + BC AC + B

11. Single Displacement
If an iron nail is placed into an aqueous solution of copper(II) sulfate, the iron displaces the copper ions in solution, and copper metal forms on the nail.

12. YouTube - Single Replacement Reactions

13. Double-Replacement Reactions
A chemical reaction that involves the exchange of positive ions between two compounds and produces either a precipitate, a gas, or water.
 AB + CD  AD + CB

14. Double Replacement
When clear aqueous solutions of lead(II) nitrate and potassium iodine are mixed, a double-displacement reaction takes place and a yellow solid appears in the mixture.
This solid is lead(II) iodine, and it precipitates out because it is insoluble in water, unlike the two reactants and the other product.

15. YouTube - Double Replacement Reactions

16. Combustion Reactions
A chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light.
Fuel + Oxygen → Carbon dioxide + Water + Heat + Light

17. Major Classes of Reactions
A combustion reaction is one in which a substance rapidly combines with oxygen to form one or more oxides.

18. Combustion
When welding is done with an acetylene torch, acetylene combines with oxygen to form carbon dioxide and water.
This combustion reaction is exothermic, and enough energy is released to melt metal.