(GED Science/Physical Science; Lesson 3)-Chemical Reactions

Please Share

Chemical Reactions

Chemical reaction of Iron, water and oxygen react to form hydrated iron or rust. The reactants here are iron, water and oxygen while the products are the hydrated iron or rust. The mass of the reactant and the product are always equal to each other. This tell us more about the law of conservation of mass which states in a chemical reaction, matter can neither be created nor destroyed.

Chemical equation

Chemical reactions are represented by chemical equations through the following:

  • In chemical equations, reactant are shown or written at the left hand side, while the product are shown or written on the left hand side.
  • As a result of the law of conversion of mass, a chemical equation must be balanced. That is the total number of element on the left side must be equal to the number of elements on the right side.
  • They show the units of each reactant and product that are involved.

Chemical reaction can be either of the following:

Endothermic reaction: is a reaction in which the reactants absorb energy from their surroundings

Exothermic reaction: is a reaction in which energy is given off usually the product (heat and light)

Activation energy: is a certain amount of energy needed to keep reaction going.


  1. Which of the following reactions absorbed energy from their surroundings? A. Activation B. Endothermic C. Exothermic D. Reactant


2. In chemical equations, …………. Are shown at the left right side

A. Activation

B. Endothermic

C. Exothermic

D. Reactant


3. …………. State matter neither be created nor destroy?

A. Conversion

B. Chemical equation

C. Matter

D. Law of conversion