Adding salt to water increases the boiling point of water due to a fundamental colligative property of matter known as boiling point elevation. Whenever a solute, such as salt, is added to a solvent, such as water, the boiling point becomes higher than that of the pure solvent. This phenomenon occurs for all solute-solvent systems, regardless of interactions between the solute and solvent molecules.Know More
The reason why the boiling point rises when solute is added to a solvent has to do with vapor pressure. A liquid boils when its vapor pressure is equal to that of the atmosphere. Vapor pressure of a solution increases as it is heated. At standard temperature and pressure, the vapor pressure of a solution is always lower than that of a pure liquid, and thus a solution must reach a higher temperature before it boils.
The degree of boiling point elevation is dependent on the amount of solute added to solution. The larger the number of salt molecules added to a given volume of water, the greater the degree of boiling point elevation. According to About.com, a person would have to add 230 grams of sodium chloride (table salt) to a liter of water in order to increase its boiling point a mere 2 degrees Celsius.Learn More
Adding sugar to water increases the boiling point. Adding 1 gram of sugar, or any other substance that does not create ions, increases the boiling point of a liter of water by 0.94 degrees Fahrenheit above its normal 212 degrees Fahrenheit.Full Answer >
Fresh water holds heat longer than salt water, because the addition of salt lowers the heat capacity of the solution relative to pure water. The lower heat capacity means that salt water both heats up and cools down more quickly than fresh water under the same conditions.Full Answer >
Sugar water freezes faster than salt water, because salt has more molecules than sugar. Normally, water freezes at 32°F, however, when a substance is added to the water, it lowers its freezing point. This is not because of the chemical nature of the substance being added, but rather the number of molecules. This is referred to as a colligative property.Full Answer >
The reason salt increases the density of water is that the mass of the resulting saltwater solution increases, while the volume is unaffected. The density of a substance is given as the mass (m) per its volume (V). The equation is density = m/V.Full Answer >