A 20 volume hydrogen peroxide solution will generally lift the hair:

• A. by 3-4 levels
• B. without any noticeable lift
• C. by more than 5 levels
• D. by 1-2 levels

Answer: (D)

Verified step by step guidance

1. Understand that 'volume' in hydrogen peroxide solutions refers to the amount of oxygen gas (O\_2) released from 1 volume of the solution under standard conditions. For example, a 20 volume solution releases 20 times its volume in oxygen gas.
2. Recognize that the strength of hydrogen peroxide solutions is often expressed in 'volumes' to indicate their oxidizing power, which correlates with their ability to lighten hair by breaking down melanin.
3. Know that typical hair lifting levels correspond to the concentration of hydrogen peroxide: a 20 volume solution usually lifts hair by about 1-2 levels, which is a mild to moderate lightening effect.
4. Compare the given options with the known effect of a 20 volume solution, noting that lifting hair by 3-4 levels or more would require higher concentrations (e.g., 30 or 40 volume solutions).
5. Conclude that the correct understanding is that a 20 volume hydrogen peroxide solution lifts hair by 1-2 levels, matching the mild lightening effect expected from this concentration.