* Chemical Reaction: Bleaching involves a chemical reaction that breaks down the melanin (pigment) in your hair. This reaction requires chemicals like hydrogen peroxide and ammonia.
* Mass Loss: During the bleaching process, some of the melanin and the bleaching chemicals themselves are either broken down into smaller volatile molecules that evaporate or are washed away. This means the total mass of the hair *decreases* after bleaching.
* Mass Gain(negligible): The mass gain from the peroxide and ammonia that react and remains in the hair is much smaller than the mass lost.
In summary: While the change in mass might be small and not easily noticeable, the process of bleaching hair results in a net loss of mass due to the chemical breakdown and removal of substances.