Question

what do these two changes have in common?
melting glass
using a large magnet to remove pieces of iron from a junkyard
select all that apply.
both are caused by cooling.
both are changes of state.
both are only physical changes.
both are caused by heating.

Explanation:

1. Analyze "melting glass": Melting glass is a physical change (changes from solid to liquid, no new substance) and is caused by heating, a change of state (solid to liquid).
2. Analyze "using a magnet to remove iron": This is a physical change (separation, no new substance), not a change of state, and not caused by heating or cooling.
3. Evaluate options:

• "Both are caused by cooling": Incorrect, melting needs heat, magnet use no cooling.
• "Both are changes of state": Incorrect, magnet use doesn't change state.
• "Both are only physical changes": Correct, both processes don't form new substances, just physical alterations.
• "Both are caused by heating": Incorrect, magnet use has no heating.

Answer:

Both are only physical changes.