It's exothermic. Potato chip is a mixture of carbohydrates and fat mostly (it also contains a little protein, and much less water than a fresh potato slice). Those elements are going to be rapidly oxidized by the oxygen in the air, and energy is released to the ambient. That ambient is released in the form of light and heat (radiant energy). However, you might need some initial heat appliance to get the reaction started, but that is due to kinetics of the process, not thermo chemistry.