Th diagrams below show physical changes in four materials after a period of time. Chemical composition of each material remained the same. Whcih material most likely changed in density.

#7 how does the structure of amino acids allow them to form a polypeptide? each amino acid has an amino group and a carboxyl group. each amino acid has a hydrogen atom and a carboxyl group. each amino acid has a carboxyl group and an r group. each amino acid has an r group and a hydrogen atom.