During a chemical reaction, two or more substances will interact with one
another and change the arrangement of their atoms. The substances reacting
are called the reactants and the substances created are called the products.
All of the atoms present in the reactants will be in the products. This is called
conservation of mass, and means that no extra atoms are created or lost. Since
this is a chemical reaction,the products will be chemically bonded, which will
make them compounds.
In a reaction, where A and B are reactants and C and D are products, it
would be written like this:
In chemical reactions, the products may have properties that are completely
different to the original reactants; they may have different appearances,
reactivity, melting points etc.