Question

what do these two changes have in common?
stapling an envelope shut
sanding a piece of wood
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 stapling an envelope: Stapling just changes the envelope's shape/position, no new substance. It's a physical change, not caused by heating/cooling.
2. Analyze sanding wood: Sanding smooths wood, changes its appearance (physical), no new substance. Not caused by heating/cooling.
3. Evaluate options:

• "Both are only physical changes": Correct, as both are physical (no chemical change, just physical alterations).
• "Both are chemical changes": Incorrect, no new substances formed.
• "Both are caused by heating": Incorrect, neither involves heating.
• "Both are caused by cooling": Incorrect, neither involves cooling.

Answer:

A. Both are only physical changes.