In carbocations, hyperconjugation occurs when the electron density from C-H bonds of adjacent alkyl groups is delocalized into the empty p-orbital of the carbocation, stabilizing it. Tertiary carbocations are more stable due to the larger number of hyperconjugative structures.

Yes, hyperconjugation stabilizes alkenes. The more alkyl groups attached to the double bond, the more hyperconjugation occurs, increasing the stability of the alkene. Tetrasubstituted alkenes are more stable than less substituted alkenes.

Greater hyperconjugation in alkenes leads to more stability, which in turn results in a lower heat of hydrogenation. The more stable the alkene (due to more hyperconjugation), the less energy is released during hydrogenation.