There are five types of general chemical reactions: Combination or synthesis, decomposition, single displacement, double displacement, and combustion.

The first video clip presents the principle behind each reaction and provides examples.

The second clip demonstrates those reactions in the laboratory.

This video was produced by edu2000

A combination reaction is a reaction in which two or more substances combine to form a new compound. The formation of hydrochloric acid (HCl) from hydrogen and chlorine in one example.

In a decomposition reaction, a compound breaks down into two or more substances. For example, the decomposition of calcium carbonate (CaCO3) into carbon dioxide (CO2) and calcium oxide.

In single displacement, one element replaces another element in a compound. For example, iron replaces copper in copper sulfate, producing iron sulfate.

In double displacement reactions, both the positive and the negative parts of two compounds are exchanged. For example, the displacement of the nitrate group and chlorine between silver nitrate and potassium chloride produces silver chloride and potassium nitrate.

Combustion occurs when a compound combines with one or more oxygen molecules to create an oxide, while releasing energy. For example, two oxygen molecules bond with methane, producing the combustion products CO2 and water.

The basis for chemical reactions is the formation of chemical bonds between substances or compounds, a bond created by an investment of energy.
We can see now that the five reactions do not occur spontaneously; they require investing a certain amount of energy (kinetic, heat, mechanical, etc.). These five reaction types are the basis for all chemical reactions.

Neutralization of an acid by an alkaline is actually a double displacement reaction. Hydrochloric acid (HCl), for instance, is neutralized by sodium hydroxide (NaOH). The hydroxide group (OH) and the hydronium group (H3O) combine to form two molecules of water (H2O), and the chlorine molecule combines with the sodium molecule to form salt.

This video clip was produced by edu2000

The second clip demonstrates the five types of reactions:

In the synthesis reaction, inserting copper into sulfur fumes yields copper sulfate. In this case, energy was invested in heating the sulfur to create the fumes.

In the decomposition reaction, heating calcium hydroxide (CaOH) produces calcium oxide (CaO) and water vapor. In this case, energy was invested in heating the calcium hydroxide.

In the single displacement reaction, heating iron oxide with aluminum results in aluminum oxide and iron. Once again, energy was invested through heating.

In the double displacement reaction, mixing potassium iodide with mercury nitrate results in potassium nitrate and mercury iodide. Mixing the two materials yields a precipitant and a solution. The precipitant is mercury iodide, the solution is potassium nitrate, and they can be separated by a high-speed centrifuge. In this case, energy was invested in mixing the materials.

In the combustion reaction, we saw that in the presence of oxygen (in the air), methane gas (CH4), which is also called cooking gas, ignites easily to form water vapor and CO2. During this combustion process, energy was invested in creating the spark. We often see soot produced by a combustion process. Soot consists of carbon by-products of incomplete combustion. Full combustion, occurring in the presence of sufficient oxygen, yields only CO2 and water.