What happens when a photon is absorbed by an object? What happens with the object when it absorbs a photon by not reflecting it. Does its mass grow or its heat grows?
 A: Also note that if the photon is absorbed, it means that there has been an electronic energy transition, whose energy difference is equal to the photon energy. The electron now is in a higher energy state. Thus higher temperature (kinetic energy). 
The photon will only be absorbed if there’s any possible energy transition in the system. 
A: Consider that 
1) Photons are massless particles
2) When an object is in thermal equilibrium, it absorbs as much radiation as it radiates itself (otherwise, its temperature would fluctuate). Absorbing the photon would then mean emitting some other radiation, called thermal radiation in this context. 
Read about black body radiation if you're interested in the subject. There's a lot of literature available (e.g. modern physics or quantum mechanics textbooks).
A: Since a photon does not have a mass, it does not grow.
If a photon is absorbed, if the heat grows depends on the wavelength of your radiation, which is vie $E = h \cdot \nu = h c/\lambda$ directly inverse proportional to the energy.
