Characteristics of acids :
$(1)$ Acids are sour in taste.
$(2)$ It turns wet blue litmus paper to red.
$(3)$ It reacts with base and forms salt and water.
$(4)$ It reacts with metal, liberating $\mathrm{H}_{2}$ gas.
Characteristics of bases :
$(1)$ Bases are bitter in taste.
$(2)$ It turns wet red litmus paper to blue.
$(3)$ It reacts with acid and forms salt and water.