What makes polar molecules good solvents

How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question views around the world. You can reuse this answer Creative Commons License. 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.

Skip to main content. Search Search. And also like in an elevator there will come a point when no more people can be added. For a solution, this point is called the saturation point and the solution itself is called a saturated solution.

At the point of saturation, no more solute will dissolve in the solvent. Rather the process of dissolving and precipitation are both occurring simultaneously and at the same rate. Generally speaking only certain molecules will dissolve in water to begin with.

The old phrase "like dissolves like" or "birds of a feather flock together" is very true with respect to what degree solutes are soluble or miscible in different solvents.

At very low concentrations, almost all molecules are somewhat soluble in all solvents. But by trend, ionic and polar solutes are more soluble in polar solvents and non-polar molecules are soluble in non-polar mostly organic solvents. The units of concentration we just discussed are used to describe the degree to which a solute is soluble in a solvent. When you place a non-polar molecule in a polar solvent like oil in water the molecules try to minimize surface contact between them.

This is actually the basis for the cells in our bodies. The lipids oily fatty acids form our cell membranes so that their non-polar tails face inward away from the polar cytoplasm and the polar heads face towards the polar cytoplasm. Although much of the explanation for why certain substances mix and form solutions and why others do not is beyond the scope of this class, we can get a glimpse at why solutions form by taking a look at the process by which ethanol, C 2 H 5 OH, dissolves in water.

Ethanol is actually miscible in water, which means that the two liquids can be mixed in any proportion without any limit to their solubility. Much of what we now know about the tendency of particles to become more dispersed can be used to understand this kind of change as well.

Picture a layer of ethanol being carefully added to the top of some water Figure below. Because the particles of a liquid are moving constantly, some of the ethanol particles at the boundary between the two liquids will immediately move into the water, and some of the water molecules will move into the ethanol.

In this process, water-water and ethanol-ethanol attractions are broken and ethanol-water attractions are formed. The attractions that form between the ethanol and water molecules are also hydrogen bonds Figure below. Because the attractions between the particles are so similar, the freedom of movement of the ethanol molecules in the water solution is about the same as their freedom of movement in the pure ethanol.

The same can be said for the water. Because of this freedom of movement, both liquids will spread out to fill the total volume of the combined liquids. In this way, they will shift to the most probable, most dispersed state available, the state of being completely mixed. There are many more possible arrangements for this system when the ethanol and water molecules are dispersed throughout a solution than when they are restricted to separate layers.

Figure below. We can now explain why automobile radiator coolants dissolve in water. These substances mix easily with water for the same reason that ethanol mixes easily with water.

The attractions broken on mixing are hydrogen bonds, and the attractions formed are also hydrogen bonds. There is no reason why the particles of each liquid cannot move somewhat freely from one liquid to another, and so they shift toward the most probable most dispersed , mixed state. We have a different situation when we try to mix hexane, C 6 H 14 , and water. If we add hexane to water, the hexane will float on the top of the water with no apparent mixing.

The reasons why hexane and water do not mix are complex, but the following gives you a glimpse at why hexane is insoluble in water.