Question

what do these two changes have in common?
bleaching hair
using polish to remove tarnish from a silver spoon
select all that apply.
both are only physical changes.
both are chemical changes.
both are caused by heating.
both are caused by cooling.

Explanation:

1. Analyze bleaching hair: Bleaching hair involves a chemical reaction (e.g., oxidation of hair pigments), so it's a chemical change, not a physical change. Heating or cooling isn't the main cause here.
2. Analyze removing tarnish: Tarnish (silver sulfide) reacts with polish (e.g., chemical agents in polish) to form new substances, so it's a chemical change. Heating or cooling isn't the cause here.
3. Evaluate options:

• "Both are only physical changes" is wrong (both are chemical).
• "Both are chemical changes" is correct (both involve chemical reactions forming new substances).
• "Both are caused by heating" is wrong (no heating involved).
• "Both are caused by cooling" is wrong (no cooling involved).

Answer:

B. Both are chemical changes.