A chemical reaction is a change where two or more substances are changed into a new substance. You can identify a chemical reaction by colour change, effervescence (bubbles), when light or heat given off, and the change is usually irreversible. There are 6 main types of chemical reactions- combustion (often called burning), synthesis, decomposition, neutralization, single replacement and double replacement. A combustion reaction is a reaction with oxygen, and heat is evolved (given off). A common example of combustion is
Hydrogen +Oxygen= Water
Synthesis is a reaction where two or more substances combine to make a compound. An example of a synthesis reaction is
Iron + Oxygen = Iron Oxide
Decomposition is the opposite of synthesis. It is the breakdown of a compound, usually through electrolysis. Electrolysis is a method of separating bonded elements or compounds by passing an electric current through them . An example of a decomposition reaction is
Calcium carbonate calcium oxide+ carbon dioxide
Single displacement is the replacement of one element with another in a compound. One of the elements is one of the reactants, and a metal replaces a metal or a non-metal replaces a non-metal. Eg.
Magnesium + zinc sulphate = magnesium sulphate + zinc
Double displacement is the swapping of elements, usually forming a solid. Eg.
Lead nitrate + sodium chloride = sodium nitrate + lead chloride
Neutralization is the reaction between an acid and alkali/base/carbonate . One example of neutralization is
Sulphuric acid + magnesium oxide = magnesium sulphate + water
Sodium hydroxide is a corrosive metallic base, and it is also called caustic soda. Nowadays, it is made along with hydrogen and chlorine, using the chloralkali process (any process that produces chlorine or a related oxidizer ) Electrolysis of a solution of sodium chloride (common salt) makes chlorine and sodium hydroxide.
2NaCl + 2H2O --electric
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