Question

what do these two changes have in common?
picking up a paper clip with a magnet
melting glass
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 "picking up a paper clip with a magnet": This is a physical change as the paper clip's chemical composition doesn't change, and it's not caused by heating or cooling (it's due to magnetic force).
2. Analyze "melting glass": Melting is a physical change (glass changes state but not its chemical nature), and it is caused by heating.
3. Evaluate the options:

• "Both are only physical changes": Correct, as both processes don't alter the chemical identity of the substances.
• "Both are chemical changes": Incorrect, as no new substances are formed in either process.
• "Both are caused by heating": Incorrect, since picking up a paper clip with a magnet isn't caused by heating.
• "Both are caused by cooling": Incorrect, as neither process is caused by cooling.

Answer:

A. Both are only physical changes.