Question

what do these two changes have in common?
baking a loaf of bread
salt and vinegar removing tarnish from a penny
select all that apply.
both conserve mass.
both are caused by cooling.
both are only physical changes.
both are chemical changes.
submit

Explanation:

1. Analyze "baking a loaf of bread": This is a chemical change as new substances (like baked dough with different properties) are formed, and mass is conserved (Law of Conservation of Mass). It involves heating, not cooling.
2. Analyze "salt and vinegar removing tarnish from a penny": Tarnish (usually copper oxide) reacts with acid in vinegar, forming new substances, so it's a chemical change. Mass is conserved here too. It's a chemical reaction, not cooling - induced, and not a physical change.
3. Evaluate options:

• "Both conserve mass": Correct, as per Law of Conservation of Mass in chemical changes.
• "Both are caused by cooling": Incorrect, baking needs heat, tarnish removal is a chemical reaction (not cooling - based).
• "Both are only physical changes": Incorrect, both are chemical changes (new substances formed).
• "Both are chemical changes": Correct, as both involve chemical reactions forming new substances.

Answer:

A. Both conserve mass, D. Both are chemical changes