How Does Adding Salt Affect the Water Level in a Closed Container?

The question of how adding a small amount of salt to 10ml of water affects the water level can be intriguing, especially when considering the complex interplay between the volume of the liquid and the solid mass.

Understanding the Concept and Initial Calculations

The original answer by Eric Ressner provides a solid foundation for understanding the behavior of salt in water. By considering the volume of undissolved salt and water, Eric correctly noted that the overall volume decreases slightly upon dissolution. However, when considering the level of the water rather than the volume, the addition of solid salt at the bottom of the container slightly elevates the water level compared to pure water.

Calculating the exact figures, considering a density of 2.16 g/cm3 for NaCl, we can derive the original volume of the salt and water mixture. The original volume is given by:

Original Volume (1000 251) / 2.16 1116.2 cm3.

The volume of 1 liter of water is 1000 cm3, and the volume of 251 grams of salt is 116.2 cm3. Comparing this to the volume of the mixture after dissolution, which is 1088 cm3, it becomes evident that while the volume decreases, the water level slightly elevates due to the solid salt settling at the bottom.

Addressing Ambiguities in the Question

Philipp Abbott's critical observation regarding the ambiguity of the term "mixed with" led to the clarification of the question. Assuming the OP meant "dissolved in," the crucial factor is the volume change upon dissolution.

Scientific Experiments and Observations

Empirical evidence, as provided by various explanations, reveals that the volume of an aqueous salt solution does not remain constant, contrary to popular assumptions. Specifically, when 4.3 moles of NaCl (sodium chloride) are dissolved in 1 liter of water, a detailed analysis by an engineer shows that the resulting density is slightly less than 1.251 g/cm3. This indicates that the solution occupies a volume of approximately 1.088 liters, which is slightly less than the original 1 liter of pure water.

The Engineer's Toolbox provides valuable data supporting this finding. The key insight here is that the density of the solution must be exactly equal to the sum of the masses of the water and the salt divided by the volume of the water for the volume to remain unchanged. This is rarely the case in practice, except for very dilute solutions or specific types of salts.

Conclusion on Volume and Level Changes

In conclusion, adding salt to water increases the water level slightly when the solid salt is added. However, the overall volume of the solution decreases upon dissolution. This subtle change is a fascinating demonstration of the physical properties of solutions and the importance of careful consideration of both volume and density in chemical processes.

For further exploration, consider performing similar calculations with different concentrations of salt or other salts, as the behavior can vary.

Keywords: salt dissolution, water volume, liquid level change