12. IE •• An ideal gas is enclosed in a cylindrical piston with a 12.0-cm radius. Heat is slowly added to the gas while the pressure is maintained at 1.00 atm. During the process, the piston moves 6.00 cm.

(a) This is an

(1) isothermal, (2) isobaric, (3) adiabatic process.

Explain.

(b) If the heat transferred to the gas during the expansion is 420 J, what is the change in the thermal energy of the gas?