Physical Changes:

* Dissolving: Salt (sodium chloride) dissolves in water, meaning the salt crystals break down into individual ions (Na+ and Cl-) that are surrounded by water molecules.

* Density Increase: The solution becomes denser than pure water. This is because the salt ions take up space and increase the mass of the solution.

* Freezing Point Depression: The freezing point of the water is lowered. This is why we use salt to melt ice on roads in winter.

* Boiling Point Elevation: The boiling point of the water is raised. This is because the salt ions interfere with the water molecules' ability to escape into the air.

Chemical Changes:

* Ionic Solutions: The dissolved salt ions make the water an electrolyte, meaning it can conduct electricity.

* Reactions: Depending on the type of salt added, it might react with the water to form new substances, like acids or bases. However, table salt (NaCl) does not react with water in this way.

Other Effects:

* Taste: The solution becomes salty.

* Osmosis: If the salt solution is separated from pure water by a semi-permeable membrane, water will move across the membrane to dilute the salt solution.

Important Considerations:

* The amount of salt added will affect the magnitude of these effects. More salt means a greater change in density, freezing point, and boiling point.

* The solubility of salt in water is limited. At room temperature, you can dissolve about 36 grams of salt in 100 ml of water. Adding more salt will just result in undissolved salt at the bottom of the container.

Overall, adding salt to water causes a variety of physical and chemical changes that make the solution different from pure water.