Which of the following best describes the impact of temperature and salinity on the density of a solution?

• A. Increasing temperature decreases density, while increasing salinity increases density.
• B. Both increasing temperature and increasing salinity increase density.
• C. Both increasing temperature and increasing salinity decrease density.
• D. Increasing temperature increases density, while increasing salinity decreases density.

Answer: (A)

Verified step by step guidance

1. Understand that density (\(\rho\)) is defined as mass per unit volume, \(\rho = \frac{m}{V}\), and it depends on both temperature and solute concentration (salinity in this case).
2. Recognize that increasing temperature generally causes liquids to expand, increasing their volume (\(V\)) while mass (\(m\)) remains constant, which leads to a decrease in density because \(\rho = \frac{m}{V}\) and \(V\) increases.
3. Understand that increasing salinity means adding more dissolved solids (solute) to the solution, which increases the mass (\(m\)) without significantly increasing the volume, resulting in an increase in density.
4. Combine these effects: increasing temperature decreases density due to expansion, while increasing salinity increases density due to added mass from dissolved solids.
5. Therefore, the best description is: Increasing temperature decreases density, while increasing salinity increases density.