Gas-phase sodium atom collisions with liquid glycerol were investigated by atomic beam scattering from normal and deuterated surfaces. The scattering signal of the recoiling effusive Na atom beam was monitored by a mass spectrometer. Because all thermally equilibrated Na atoms ionize into the liquid surface, this system was uniquely suited to interrogate the subtle kinematic effect of glycerol deuteration on the collisional energy transfer process within the impulsive scattering regime. An interplay of kinematic and vibrational effects explains the Na scattering behavior from variously deuterated glycerol surfaces, extending our fundamental understanding of collisional energy transfer, and ultimately, chemical reaction dynamics.