Left hand / right hand?
Year 13 chemistry students will find out that molecules can be "handed". This is the result of property known as chirality.
When a carbon atom within a molecule is bonded to four different groups ( e.g. methyl, hydrogen, amino, and carboxylic acid) the molecule can exist in two different forms (enantiomers) . Each enantiomer is a mirror image of the other.
The two forms (enantiomers) of the same molecule are almost identical but cannot be superimposed on one another. They are non-superimposable mirror images.
You can zoom and rotate the two molecules below. However much you rotate either of them - they will never be identical...
L - Glutamic acid
D - Glutamic acid