Question

Define chemical reaction.

Answer 1

When one or more elements or compounds (known as reactants) undergo a chemical change with absorption or evolution of energy to give new substances(known as products), this change is known as a chemical reaction.

Example-

$\underset{\mathrm{Magnesium}}{2\mathrm{Mg}}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}}+\underset{\mathrm{Heat}}{∆}$

2 magnesium atoms react with a molecule of oxygen producing 2 molecules of the compound magnesium oxide releasing some heat in the process.

Here magnesium atoms and oxygen are reactants and magnesium oxide is the product.