Question

Heat can be used to straighten hair primarily because it: a. Breaks peptide bonds b. Breaks ionic bonding c. Inhibits Van der Waals forces d. Inhibits covalent bonds e. Breaks disulfide bonds

Answer 1

Option e is the correct answer

Heat can be used to straighten hair primarily because it breaks disulfide bonds. The plates of the iron are usually heated to high temperatures, generally between 300 and 500 degrees Fahrenheit.
When hair is passed through the iron quickly, while being held tight and straight, the extreme heat causes the disulphide bonds to break. This breakage allows the keratin chains to move around slightly and assume a position that results in straightened hair. When the hair cools down, the disulphide bonds between the keratin are reformed. Because the keratin molecules are in different positions when the bonds are reformed, the hair stays in the straightened shape for a long period of time.