How does increased salinity affect the density of water?

• A. It increases the density of water.
• B. It has no effect on the density of water.
• C. It first increases and then decreases the density of water.
• D. It decreases the density of water.

Answer: (A)

Verified step by step guidance

1. Understand that density is defined as mass per unit volume, given by the formula \(\rho = \frac{m}{V}\), where \(\rho\) is density, \(m\) is mass, and \(V\) is volume.
2. Recognize that when salinity increases, more dissolved salts (solutes) are added to the water, which increases the total mass of the solution without significantly increasing its volume.
3. Since the mass increases while the volume remains nearly constant or changes very little, the overall density of the water increases.
4. Consider that pure water has a certain density, and adding salt makes the solution denser because the dissolved ions add mass but do not proportionally increase the volume.
5. Conclude that increased salinity leads to an increase in the density of water, which is why seawater is denser than freshwater.