Chemistry and Product Knowledge
What this domain tests
Chemistry and product knowledge tests pH, chemical bonds, mixtures, surfactants, oxidation and reduction, and safe product handling.
Core rules
- The pH scale runs from 0 to 14: below 7 is acidic, 7 is neutral, above 7 is alkaline. Hair and skin prefer mildly acidic products.
- Chemical bonds include ionic, covalent, hydrogen, and disulfide. Disulfide bonds are changed by perms and relaxers.
- Solutions, suspensions, and emulsions differ in how ingredients are mixed; surfactants allow oil and water to mix and lift soil.
- Oxidation adds oxygen or removes hydrogen; reduction adds hydrogen or removes oxygen.
- Never mix products unless the manufacturer directs it. Read the SDS for hazards and first aid.
Worked example
A shampoo reads pH 5.5 and a perm solution reads pH 9. The shampoo is acid-balanced and helps close the cuticle; the perm solution is alkaline and swells the cuticle so the reducing agent can reach the cortex. The reasoning is that pH controls cuticle swelling and product activity.
Traps
Reversing acid and alkaline; confusing oxidation and reduction; mixing developer with an incompatible product; ignoring the SDS; assuming “natural” means safe.
Exam focus
Use pH and bond chemistry to explain what a product does to hair, skin, or nails.