Some examples of physical changes are:
Breaking a glass
Chopping wood
Tearing paper
Mixing sand and water
Melting an ice cube
These all are physical changes because the composition of the matter does not change.
What happened after that ? If you don’t mind me asking .
The amino acids are the molecules where we can found the carboxyl group (-
), amino group (-
), hydrogen atom (H) and a residual R-group. On the structure of the residual R-group the name of the amino acid depends. Like if R is hydrogen (H) the amino acid is alanine; If R- group is a phenyl group i.e. 
, the compound is called phenyl alanine. The structure of the general amino acid skeleton can be shown as-
