Question

what do these two changes have in common?
mixing lettuce and salad dressing
adding dish soap to water in a sink
select all that apply.
both are only physical changes.
both conserve mass.
both are chemical changes.
both are caused by heating.

Explanation:

1. Analyze "mixing lettuce and salad dressing": This is a physical change as no new substance is formed, just a mixture. Mass is conserved (mass of lettuce + dressing = mass of mixture). No heating involved.
2. Analyze "adding dish soap to water": Also a physical change (mixing, no new substance chemically formed), mass is conserved (mass of soap + water = mass of soapy water), and no heating.
3. Evaluate options:

• "Both are only physical changes": Correct, as both are physical (no chemical reaction, just mixing).
• "Both conserve mass": Correct, by law of conservation of mass, in physical changes mass is conserved.
• "Both are chemical changes": Incorrect, no chemical reactions occur.
• "Both are caused by heating": Incorrect, neither involves heating.

Answer:

A. Both are only physical changes, B. Both conserve mass