Reaction Combination Decomposition Double Displacement Redox Notes Chapter 1 Chemical Reactions and Equations Science

Chemical Equations:  It is the symbolic representation of a chemical reaction where the reactant entities are given on the left hand side and the product entities on the right hand side of the equation. In complete chemical equation all reactants and products are written along with their physical state. A chemical equation must be balanced so that it can follow the law of conservation of mass. For example

Balanced Chemical equation: If in a chemical equation the total number of atoms in the reactant side are equal to the total number of atoms in the product side then the chemical reaction is said to be balanced.

Combination Reaction: If in a Chemical equation, two or more reactants combine to form a single product then it is known as combination reaction.

Decomposition reaction: If in a chemical reaction a single substance decomposes to form two or more substances then it is known as decomposition reaction.

Displacement Reaction: If in a chemical equation, more reactive elements displaces a less reactive element from its compound then it is known as displacement reaction.

Double displacement reaction: If in a chemical reaction exchange of ions takes place then it is known as double displacement reaction

Precipitation Reaction: A white coloured substance which is insoluble in water also known as precipitate is formed during a chemical reaction then the reaction is known as precipitation reaction

In this reaction Barium sulphate is a white colour precipitate.

Oxidation Reaction: It is a chemical reaction in which gain of oxygen or loss of hydrogen takes place. For example in the following reaction copper is oxidised to become copper oxide.

Reduction Reaction: It is a chemical reaction in which loss of oxygen or gain of hydrogen takes place. For example in the following reaction copper oxide is reduced to become copper.

Redox Reaction or Oxidation-Reduction reaction: The chemical reaction in which both oxidation and reduction takes place is known as Redox reaction. For example in the following reaction Hydrogen is oxidised to become water and copper oxide is reduced to become copper.

Corrosion: It is the process in which metals are slowly eaten up by the action of air moisture or chemicals. For example rusting is a form of corrosion in which iron is eaten up by the action of air and moisture and a reddish brown coating of iron oxide is formed as shown in the following chemical reaction.

Rancidity: When the substance containing oils and fats are exposed to air they get oxidised and become rancid due to which their smell, taste and colour change. This process is known as rancidity. For example when a when butter is kept open for a long time then its smell and taste gets changed.