A chemical reaction is a process in which substances, called reactants, undergo a transformation to form new substances, called products with entire new properties. This involves breaking and forming bonds between atoms.

Reactants are the starting substances that undergo a chemical change in a reaction, while products are the new substances formed as a result of that chemical change.

For example, zinc reacts with sulphuric acid to produce zinc sulphate and hydrogen gas.

\(\rm Zn\)+\(\rm dil.H_{2}SO_{4}\) → \(\rm ZnSO_{4}\) + \(\rm H_{2}\)