Question

based on our discussion in class, at the molecular level, why is salt water more dense than fresh water?

Explanation:

Salt water contains dissolved salt (sodium - chloride ions). These ions add mass to the same volume of water compared to fresh water which has no such dissolved substances. Density is mass per unit volume. With more mass in the same volume, salt water has a higher density.

Answer:

Salt water contains dissolved salt ions that add mass to the same volume of water, increasing its density compared to fresh water.