What elements change water density?

The correct answer highlights the key factors that affect water density: temperature and salinity. As temperature increases, water typically expands, leading to a decrease in density. Conversely, when the temperature decreases, water contracts, resulting in increased density.

Salinity also plays a significant role in determining water density. When salt is dissolved in water, it increases the mass of the water without significantly changing its volume. This increase in mass for a given volume results in higher density. Therefore, when salinity rises, the density of the water increases.

Understanding these two elements—temperature and salinity—is crucial for comprehending how water behaves in different environmental conditions. They are vital for various scientific studies and applications, including oceanography, climate science, and marine biology. Other options, while they may have relevance to some aspects of water behavior, do not encompass the primary factors that directly influence the density of water in a straightforward manner as temperature and salinity do.