Why specific heat capacity of a gas at constant pressure is greater than specific heat capacity at constant volume

📌When the gas is heated at constant volume there is no work done against external pressure

📌Hence all the heat supplied is used in raising the temperature of the gas 

📌But when the gas is heated at constant pressure , volume of the gas changes.

📌Due to this, part of the supplied heat is used by the gas to expand against external pressure and remaining part of heat supplied is used to raise the temperature.

📌Because of this, for the same rise in temperatures ,the heat to be supplied at constant pressure is greater than  that for heating at constant volume. 

Hence, specific heat capacity of a gas at constant pressure is greater than specific heat capacity at constant volume.