National League for Nursing (NLN) Science Practice Exam

If a salt is added to water, what is likely to happen?

1. The boiling point will increase and the freezing point will decrease.

2. The boiling point will increase and the freezing point will increase.

3. The boiling point will decrease and the freezing point will decrease.

4. The boiling point will decrease and the freezing point will increase.

The correct answer is: The boiling point will increase and the freezing point will decrease.

When salt is added to water, it dissociates into its constituent ions, which affects the physical properties of the solution. One key concept involved here is colligative properties, which are properties that depend on the number of solute particles in a solvent rather than the identity of the solute. By adding a solute such as salt to water, you elevate the boiling point. This is due to the presence of dissolved ions, which disrupt the formation of vapor above the liquid surface, thus requiring a higher temperature to boil. This phenomenon is known as boiling point elevation. At the same time, the freezing point of the solution decreases, a process known as freezing point depression, which occurs because the solute ions hinder the formation of a solid structure, such as ice. Therefore, it takes a lower temperature to achieve a state where the water can solidify. In summary, the addition of salt to water will lead to an increase in the boiling point and a decrease in the freezing point, making the first choice accurate.