The reaction between an acid and a base is known as neutralization. Salt and water are produced in this process with the evolution of heat.
Acid + Base → Salt + Water + (Heat is evolved)
As for example, when sodium hydroxide (NaOH) is treated with sufficient amount of hydrochloric acid (HCl), a neutralization reaction takes place. Both NaOH and HCl neutralize their effects and form a salt sodium chloride (NaCl) and water (H2O) with the evolution of heat energy.
NaOH + HCl → NaCl + H2O + (Heat is evolved)
Lime water is a dilute solution of Ca(OH)2, which is a base. Sulphuric acid (H2SO4) react with limewater to give salt and water along with the evolution of heat. Because it is a neutralisation reaction, the reaction mixture will become hot.