Dissolving salt in water is reversible because you can separate salt and water without changing their properties. For example by evaporation. On the other hand, some salt and water vapor can form a salt solution. For example CaCl2, which is used to bind road dust. As for volume change, I think it is small, because the salt ions are in between and surrounded by the water molecules. Each ion is given a "shell" of water molecules.

Dr Arne Andersen thank you for your contribution to the discussion

Dissolving a solid in liquid, such as table salt in water, is a physical change because only the state of the matter has changed. Physical changes can often be reversed. Allowing the water to evaporate will return the salt to a solid state. If you can get back the substances you started the reaction with, that's a reversible reaction. A reversible change might change how a material looks or feels, but it doesn't create new materials. As reversible reactions include dissolving, evaporation, melting and freezing. Mixing of salt in water is a change that can be reversed by heating and melting of salt. Mixing salt in water is a change that cannot be reversed. If we dissolve a salt in water, the salt will dissociate into its constituent ions which means that some new substance is being formed. It is an irreversible process and there will be either change in temperature, energy, evolution of gas or precipitate formation.No volume of water does not reduce when you add salt the salt molecules will be upholder by water molecules between their gaps so, volume of water is neither increases nor decreases when salt is added. Adding salt (NaCl) to water actually does increase the volume a little bit, although by less than the volume of the added salt. The Na+ and Cl- ions fit nicely in the water, not taking up much room. When sodium chloride dissolves in water to make a saturated solution there is a 2.5 per cent reduction in volume. Saturated salt solution has a density of 1.202 g/ml. Ask students why they think saltwater is denser than regular water. Saltwater has a higher mass because of the added salt but still occupies the same amount of space in a container that regular water would, and hence is denser.

Dissolving salt in water is a reversible change because the salt can be separated from the water by evaporating the water. The salt will remain behind as a solid.

The volume of water will increase slightly when salt is added to it. This is because the salt molecules take up space in the water. The amount of increase in volume is typically small, but it can be significant for concentrated salt solutions.

The reason why dissolving salt in water is a reversible change is because the salt molecules do not chemically react with the water molecules. Instead, the salt molecules simply disperse evenly throughout the water, forming a solution. This means that the salt can be separated from the water by simply evaporating the water.

The reason why the volume of water increases when salt is added to it is because the salt molecules take up space in the water. The salt molecules are not as dense as water molecules, so they displace some of the water molecules. This results in a slight increase in the volume of the solution.

The amount of increase in volume will depend on the amount of salt that is added to the water. A small amount of salt will cause a small increase in volume, while a large amount of salt will cause a larger increase in volume.

Here are some additional details about the reversible nature of dissolving salt in water:

• The process of dissolving salt in water is exothermic, meaning that heat is released. This heat energy helps to separate the salt molecules from each other and disperse them throughout the water.
• The rate of dissolving salt in water depends on a number of factors, including the temperature of the water, the surface area of the salt, and the stirring rate.
• The solubility of salt in water is the amount of salt that can dissolve in a given amount of water at a given temperature. The solubility of salt in water increases with temperature.

Dr Murtadha Shukur thank you for your contribution to the discussion

Adding salt to water makes the water denser. As the salt dissolves in the water, it adds mass (more weight to the water). This makes the water denser and allows more objects to float on the surface that would sink in fresh water. About 3.5 percent of the weight of seawater comes from the dissolved salts. Adding salt (NaCl) to water actually does increase the volume a little bit, although by less than the volume of the added salt. The Na+ and Cl- ions fit nicely in the water, not taking up much room. This happens because water molecules are not tightly packed and have space between them hence when we dissolve the salt in it the salt particles occupy the space between the molecules of the water thus the water level doesn't rise up. Dissolution of sugar and salt into water is a reversible process because sugar and salt can be retrieved upon heating the solution, thus evaporating water and leaving sugar and salt behind. When salt is dissolved in fresh water, the density of the water increases because the mass of the water increases. When sugar dissolves in water, the sugar molecules take up space between the water molecules. Thus, they do not occupy any extra space. Hence volume of solution does not change. When salt dissolves in water, the tiny salt particles occupy the spaces between the water particles. There won't be any increase in volume of water.When we add a solid substance to a liquid, the particles solid get into the spaces between the liquid particles. So, since the solids occupy the spaces inside liquid atoms, the volume of the liquid doesn't increase.