As the attractions from the water molecules and their motion pulls the ions apart, the sodium chloride crystal dissolves. The positive areas of the water molecules surround the negative Chloride ions.

Heat can help some substances dissolve faster in water. Salt, for example, will dissolve quicker in hot water than in cold water. When a substance dissolves, it might look like it has disappeared ...

The first contains a fine iron powder, salt, and water in a pouch that is permeable to air. When it is exposed to air, the iron begins to rust. This rusting process produces heat. The second contains ...