There are five kinds of reactions. They are combination reaction, decomposition reactions, single replacement reaction, double replacement reaction and combustion reactions. These reactions have their own specialty and different looks.
The combination reaction is a kind of chemical change in which two or more substances react to form a single new substance. Such as 2MG + O2 –> 2 MgO. As you see from the reaction, there are too kind of element that combine together inorder to form a new substance. Notice the ratio of types of the reactant and the product is always 2:1. The product may not be fixed, which means the same reactant may produce different product. Such as Fe+ S–> FeS, 2Fe + 3S –>Fe2S3.
The decomposition reaction is a kind of chemical change in which one substance breaks down into two or more products. Such as 2Mg0–> 2Mg +O2. As you see from the reaction, the reactent MgO get breaks down into two substance, Mg and O2. In order to get the same product, the reactant may not be the same. Such as Fe2S3 and FeS can both breaks into Fe ans S.
The Single replacement reaction is a kind of chemical change in which one element take the place of another element in a compound. You can find that both the reactant and the product is composed of a single element and a compound. Remember, the single replacement reaction is only happened when the element have the larger reactivity. The order of the reactivity (of some element) is Li, K, Ca, Na, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag. If the element has the lower reactivity then the one in the compound, the reaction will not be formed. An example of a single replacement reaction is Br2+ NaI –> NaBr + I2.
There are some reaction won’t be form because of reactivity. For example Br2 + NaCl–> no reactions
The Double replacement reaction is a kind of chemical change in which one element in one compound exchange with another element in another compound. You can find that both the reactant and the product is composed of two compounds. Remember, the double replacement reaction is only happened when one of the following is usually true:
1. One of the products is soluble from solution, just like Na2S + Cd(No3)2 –> CdS+ 2NaNo3;
2. One of the products is gas.
3. One of the products is a molecular compound such as water.
The Combustion Reaction is the most simple one. It was just a compound formed with C and H (some time with O) react with oxygen to form CO2, H2O and a lot of energy.
There are also many different kinds of reaction that was not included in the article. If you want to learn about it, please just keep studying and keep fighting on.