What kind of substances dissolve in water

That is where water helps out; being such a great solvent, water washing through the kidneys dissolves these substances and sends them on the way out of our bodies. This diagram shows the positive and negative parts of a water molecule. It also depicts how a charge, such as on an ion Na or Cl, for example can interact with a water molecule. At the molecular level, salt dissolves in water due to electrical charges and due to the fact that both water and salt compounds are polar, with positive and negative charges on opposite sides in the molecule.

The bonds in salt compounds are called ionic because they both have an electrical charge—the chloride ion is negatively charged and the sodium ion is positively charged.

Likewise, a water molecule is ionic in nature, but the bond is called covalent, with two hydrogen atoms both situating themselves with their positive charge on one side of the oxygen atom, which has a negative charge.

When salt is mixed with water, the salt dissolves because the covalent bonds of water are stronger than the ionic bonds in the salt molecules. The positively-charged side of the water molecules are attracted to the negatively-charged chloride ions and the negatively-charged side of the water molecules are attracted to the positively-charged sodium ions.

Essentially, a tug-of-war ensues with the water molecules winning the match. Water molecules pull the sodium and chloride ions apart, breaking the ionic bond that held them together. After the salt compounds are pulled apart, the sodium and chloride atoms are surrounded by water molecules, as this diagram shows.

Once this happens, the salt is dissolved, resulting in a homogeneous solution. It means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

It is water's chemical composition and physical attributes that make it such an excellent solvent. Water molecules have a polar arrangement of the oxygen and hydrogen atoms—one side hydrogen has a positive electrical charge and the other side oxygen had a negative charge. This allows the water molecule to become attracted to many other different types of molecules.

Water can become so heavily attracted to a different molecule, like salt NaCl , that it can disrupt the attractive forces that hold the sodium and chloride in the salt molecule together and, thus, dissolve it. The charges associated with these molecules form hydrogen bonds with water, surrounding the particle with water molecules.

This is referred to as a sphere of hydration, or a hydration shell, and serves to keep the particles separated or dispersed in the water. When ionic compounds are added to water, individual ions interact with the polar regions of the water molecules during the dissociation process, disrupting their ionic bonds. Dissociation occurs when atoms or groups of atoms break off from molecules and form ions. Since many biomolecules are either polar or charged, water readily dissolves these hydrophilic compounds.

Water is a poor solvent, however, for hydrophobic molecules such as lipids. All this interaction suspends the solute molecule in a sea of water molecules; it disperses and dissolves easily. Electrons in the bonds between identical atoms H-H are shared uniformly, so the electrons spend equal amounts of time around each atomic center. These covalent bonds are non-polar. Electrons shared between unlike atoms are not shared equally, one atom gets more of the common electrons and is thus slightly negatively charged.

The other atoms gets less than a full share of the electrons and is thus slightly positively charged. Substances which dissolve easily and readily in water sugar, salt, etc. On the other hand, some solutes are non-polar and do not have any positive or negative charges. Water molecules are not attracted to these types of molecules and, in fact, are sometimes repelled by them. Although tiny amounts of these substances plastic, oil, etc.