Question

what do these two changes have in common? salt and vinegar removing tarnish from a penny making jam select all that apply. both are caused by heating. both are caused by cooling. both conserve mass. both are only physical changes.

Explanation:

1. "Both are caused by heating": Removing tarnish with salt/vinegar is a room-temperature chemical reaction, so this is incorrect.
2. "Both are caused by cooling": Jam-making requires heating to cook fruit/evaporate water, so this is incorrect.
3. "Both conserve mass": The law of conservation of mass applies to all chemical and physical changes; no mass is created or destroyed in either process, so this is correct.
4. "Both are only physical changes": Tarnish removal is a chemical reaction (acid reacting with copper oxide), and jam-making involves chemical changes (like pectin gelation), so this is incorrect.

Answer:

Both conserve mass.