Question

what do these two changes have in common?
bleaching hair
a log decomposing in the woods
select all that apply.
both conserve mass.
both are changes of state.
both are chemical changes.
both are only physical changes.

Explanation:

1. Analyze "Both conserve mass": According to the law of conservation of mass, in any chemical or physical change, mass is conserved. Both bleaching hair (involves chemical reactions like breaking bonds in hair pigments) and log decomposition (microorganisms break down organic matter) are processes where mass is conserved as atoms are rearranged, not created or destroyed.
2. Analyze "Both are changes of state": A change of state (like melting, freezing, vaporization) involves a physical change in the state of matter (solid, liquid, gas) without changing the chemical identity. Bleaching hair is a chemical change (alters hair's chemical structure), and log decomposition is also a chemical change (breaks down wood into new substances like carbon dioxide, water, and organic compounds). So this is incorrect.
3. Analyze "Both are chemical changes": Bleaching hair uses chemicals (like hydrogen peroxide) to break down hair pigments, creating new substances. Log decomposition is a biological - chemical process where fungi, bacteria, etc., break down the log's organic matter into simpler substances (new chemicals are formed). So both are chemical changes.
4. Analyze "Both are only physical changes": A physical change doesn't create new substances (e.g., cutting hair, melting ice). But bleaching hair and log decomposition both create new substances, so they are not physical changes. So this is incorrect.

So the correct options are "Both conserve mass" and "Both are chemical changes".

Answer:

A. Both conserve mass
C. Both are chemical changes