White sugar and table salt are very confusing and you must have fallen into the scene where your baked goods are “horrible” because of these “twins” with a similar appearance.
But when you add a little water, these twins become completely different. Both the salt and the sugar crystals begin to dissolve in the water, but the sugar gets sticky and the salt doesn’t . Why so?
Hydrogen is the key to sugar’s stickiness.
According to How Stuff Works, Hydrogen is the key to sugar’s stickiness . Sugar is a solid, its molecules made of carbon, hydrogen and oxygen atoms. The sugar crystals are intact and do not stick together – you can easily sift the sugar. But in the presence of liquid, the previously strong oxy-hydrogen bonds in the sugar will begin to break down and the liquid hydrogen atoms will look for something else to stick to.
Some of the hydrogen atoms will stick to the nearest surface, some will pick up the hydrogen molecules in the liquid, and some will bond with another hydrogen or oxygen atom in the sugar. As a result it produces a sticky solution.
Meanwhile, salt is made of sodium and chlorine, so when it dissolves in water there is no hydrogen floating around to stick to anything.
But what about water? Its molecules are also partly made up of hydrogen – why doesn’t it become sticky like sugar when combined with some other substance? This has to do with the fact that sugar has a more complex structure than water. A sugar molecule contains 12 carbons, 22 hydrogen atoms, and 11 oxygen atoms – and more hydrogen bonds than a water molecule. When the bonds in sugar are broken, there is more opportunity for the molecules to bond with whatever they come into contact with, including other sugar molecules.
On the other hand, each water molecule consists of only two hydrogen atoms and one oxygen atom, so it does not have many “stick points”. Therefore, the dissolved sugar will be sticky and the water itself will not.