Between-Molecule Attractions

Why objects exist. For objects that are big enough for humans to see to exist, there must be forces that bond molecules to other molecules. The molecules of a specific substance (for example, salt) are attracted to other molecules of the same kind to form that substance. This is why we can see a drop of water or a grain of salt.

Oppositely-charged areas of different molecules are attracted to each other due to electric force. 

• For example, individual NaCl (table salt) molecules are attracted to each other through electric forces from oppositely-charged sides of molecules. The negative (Cl) sides of the molecules and positive (Na) sides of the molecule attract each other. (This is represented below.)

• Individual water molecules are attracted to each other because of the electric force. Oppositely-charged sides of water molecules attract. This idea is shown in the picture below. The negatively charged parts of molecules (represented by red) attract the positively charged parts of other molecules (represented as blue). And vice versa.

• The attractions between water molecules form water droplets that are large enough to see! If there were no attractions between H₂O molecules, they would all separate from each other. You wouldn't be able to see them at all because molecules are way too tiny to see with your eyes.

Sugar molecules (Advanced): Individual sugar molecules—such as sucrose—are attracted to each other. These attractions are caused by electric forces from oppositely-charged areas of different sugar molecules. That is, areas of sucrose molecules that are negatively charged are attracted to positively charged areas of other sucrose molecules (and vice versa).

Sugars are much more complex molecules than salts (such as NaCl, which is made of only two atoms). Because of this, the electric force attractions that hold individual sugar molecules together are harder to show. But the picture below shows ("space-filling" models of) a single sucrose molecule (left) and two sucrose molecules (right).