Question

what do these two changes have in common?
salt and vinegar removing tarnish from a penny
chemicals in a battery reacting to power a flashlight
select all that apply.
both are changes of state.
both conserve mass.
both are caused by cooling.
both are chemical changes.

Explanation:

1. Analyze "salt and vinegar removing tarnish from a penny": This is a chemical reaction (tarnish reacts with the solution), and in all chemical reactions, mass is conserved (Law of Conservation of Mass). It's a chemical change, not a change of state (no phase change like solid to liquid) and not caused by cooling.
2. Analyze "chemicals in a battery reacting to power a flashlight": This is a chemical reaction (electrochemical), mass is conserved, it's a chemical change, not a change of state, and not caused by cooling.
3. Evaluate options:

• "Both are changes of state": Incorrect, as both are chemical reactions, not phase changes.
• "Both conserve mass": Correct, due to the Law of Conservation of Mass in chemical reactions.
• "Both are caused by cooling": Incorrect, these reactions aren't driven by cooling.
• "Both are chemical changes": Correct, as both involve chemical reactions (tarnish removal is a reaction, battery reaction is electrochemical).

Answer:

Both conserve mass, Both are chemical changes