What condition is necessary for an sp3 hybridized atom to be asymmetric?

An sp³ hybridized carbon atom is an atom that combined all of it's atomic orbitals, (1 s-orbital and 3 p-orbitals) into four sp³ hybridized molecular orbitals. An sp³ hybridized carbon atom will form four bonds, one with each sp³ orbital. The geometry of a carbon atom with four different substituents will be tetrahedral in nature. There is only one substitution pattern that leads to an asymmetric sp³ hybridized carbon atom.

A carbon center with the structure CH₄, has four of the same substituents and is symmetrical with two plans of symmetry. If we change one substituent, to CH₃Cl, we lose one plane of symmetry, but the other plane of symmetry still remains, therefore, it is not asymmetric. Changing the molecule to contain three different substituents, CH₂ClBr, creates a molecule that still has a single plane of symmetry. Therefore, the only way to have an asymmetric carbon center is to have four different substituents which will disrupt all planes of symmetry.

A molecule of the form CHClBrF, or simply with four different substituents, will be completely asymmetric as there are no planes of symmetry in this molecule.

They can measure  the amount of energy gained or lost