Final answer:
The statement is true; hydroxide relaxers are strong alkalis that can indeed cause the hair to swell significantly as they break down disulfide bonds within the hair structure.
Step-by-step explanation:
The statement that hydroxide relaxers are very strong alkalis that can swell the hair up to twice its normal diameter is true. Hydroxide relaxers work by penetrating the hair shaft and breaking down the disulfide bonds that give the hair its shape, this process is also described as a reduction reaction. This breaking of disulfide bonds leads to the hair swelling and softening, which then allows it to be reshaped. Care must be used, as the high pH of these substances can also cause the hair to weaken and break if left on for too long.
These relaxers are very similar in chemical nature to substances like sodium hydroxide, commonly found in alkaline drain cleaners. When sodium hydroxide dissolves in water, it creates a highly basic solution capable of breaking down organic matter such as hair, which is why it's used in products like Drano. The high pH of hydroxide in relaxers is what allows them to disrupt the disulfide bonds in hair, similar to how drain cleaners dissolve hair clogs.
After relaxing the hair, an oxidizing agent, typically a dilute solution of hydrogen peroxide, is applied to neutralize the reaction and reform the disulfide bonds in their new positions. This ensures that the new shape of the hair is maintained until the hair grows out.