How much does salt water weigh per cubic foot compared to freshwater?

To understand why the choice of 64 (saltwater) and 62.5 (freshwater) is the correct answer, it's important to recognize the density differences between saltwater and freshwater. Freshwater has a density of approximately 62.5 pounds per cubic foot, while saltwater, which contains dissolved salts that increase its density, weighs about 64 pounds per cubic foot.

This discrepancy occurs because the presence of salts in seawater increases the mass of the water without significantly changing its volume, leading to a higher weight per unit volume compared to freshwater. Understanding these differences is essential for divers, as it affects buoyancy, which plays a crucial role in diving practices and safety.

This comparison helps to illustrate the concept of density in various types of water, emphasizing the importance of knowing how different environments can affect underwater experiences.