Question

1. a student measures the masses of two liquids. one liquid is 14 grams and the other liquid is 18 grams. then the student pours both liquids into an open beaker and observes the liquid bubble for a few minutes. when she measures the mass of the liquid in the beaker it has a mass of 29 grams. this could be because molecules ________. a. got smaller. c. were destroyed. b. escaped from the beaker. d. moved closer together.

Explanation:

1. First, calculate the initial total mass of the two liquids: \(14 + 18 = 32\) grams.
2. The final mass is 29 grams, which is less than 32 grams.
3. Analyze each option:

• Option A: Molecules getting smaller doesn't change the total mass (mass is conserved at molecular level, size of molecules doesn't affect total mass measurement here). Eliminate A.
• Option B: If molecules escaped from the open beaker (like evaporation, since it's open), the total mass would decrease. This matches the mass change (32→29).
• Option C: Molecules can't be destroyed in a physical process (mixing/possible evaporation is physical, not chemical decomposition here), and mass conservation in chemistry says atoms/molecules aren't destroyed. Eliminate C.
• Option D: Molecules moving closer together (like condensation or mixing with no escape) would keep mass same (or change due to density but mass of substance remains; here mass decreased, so D is wrong as it wouldn't cause mass loss). Eliminate D.

Answer:

B. escaped from the beaker.