This document may be freely reproduced and distributed for non-profit educational purposes. Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents. Hydrogen Bonds Make Water Sticky. Water has an amazing ability to adhere stick to itself and to other substances.
Hydrogen Bonds. Hydrogen bonds form when hydrogen atoms covalently bonded to nitrogen N , oxygen O , or fluorine F in the form of covalent compounds such as ammonia NH 3 , water H 2 O and hydrogen fluoride gas HF. In these molecules, the hydrogen atoms do not pull as strongly on the shared electrons as the N, O, or F atoms.
Therefore, the molecules are polar; the hydrogen atoms become positively charged and are able to form hydrogen bonds to negative ions or negatively charged parts of other molecules such as the N, O, and F atoms that become negatively charged in these compounds. Hydrogen bonds are not true bonds like covalent bonds or ionic bonds.
Hydrogen bonds are attractions of electrostatic force caused by the difference in charge between slightly positive hydrogen ions and other, slightly negative ions. These attractions are much weaker than true ionic or covalent bonds, but they are strong enough to result in some interesting properties.
In the case of water, hydrogen bonds form between neighboring hydrogen and oxygen atoms of adjacent water molecules. The attraction between individual water molecules creates a bond known as a hydrogen bond. See Fig. A molecule of water has two hydrogen atoms. Both of these atoms can form a hydrogen bond with oxygen atoms of different water molecules. Every water molecule can be hydrogen bonded with up to three other water molecules See Fig. However, because hydrogen bonds are weaker than covalent bonds, in liquid water they form, break, and reform easily.
Thus, the exact number of hydrogen bonds formed per molecule varies. Molecules of pure substances are attracted to themselves. This sticking together of like substances is called cohesion. Depending on how attracted molecules of the same substance are to one another, the substance will be more or less cohesive. Hydrogen bonds cause water to be exceptionally attracted to each other.
Emergency Management. Survey Manual. Adhesion and cohesion are important water properties that affects how water works everywhere, from plant leaves to your own body. Just remember Cohesion : Water is attracted to water, and Adhesion : Water is attracted to other substances. I used to wake up in a cold sweat because I could not get the concepts of water adhesion and cohesion clear in my mind.
If you have that problem, too, then read on to learn about these important properties of water Cohesion : Water is attracted to water Adhesion : Water is attracted to other substances. Adhesion and cohesion are water properties that affect every water molecule on Earth and also the interaction of water molecules with molecules of other substances. Essentially, cohesion and adhesion are the "stickiness" that water molecules have for each other and for other substances.
A water drop is composed of water molecules that like to stick together-an example of the property of cohesion. In the picture of pine needles above, the water droplets are stuck to the end of the pine needles-an example of the property of adhesion.
Also noticeable in this picture is the effect that gravity has on the water drops. Gravity is working against both adhesion and cohesion, trying to pull the water drop downward.
Adhesion and cohesion are winning the battle so far, as the drops are sticking to the pine needles. If you just look at the picture of the water drop sitting of the leaf, you might think the water drop has a "skin" holding it into a sort of flattened sphere although there is nothing flat about a water drop in outer space.
It turns out that this surface tension is the result of the tendency of water molecules to attract one another. The natural form of a water drop occurs during the "lowest energy state", the state where the atoms in the molecule are using the least amount of energy.
For water, this state happens when a water molecule is surrounded on all sides by other water molecules, which creates a sphere or ball perfectly round if it was in outer space.
On Earth, the effect of gravity flattens this ideal sphere into the drop shape we see. Although you may have heard of a "skin" where water meets the air, this is not really an accurate description, as there is nothing other than water in the drop.
What is the shape of a raindrop? Are they really tear-shaped? Maybe not. Find out here. Water is highly cohesive—it is the highest of the non-metallic liquids. Water is sticky and clumps together into drops because of its cohesive properties, but chemistry and electricity are involved at a more detailed level to make this possible.
More precisely, the positive and negative charges of the hydrogen and oxygen atoms that make up water molecules makes them attracted to each other. If you've played with bar magnets you will know that the north pole of one magnet will repel the north pole of another magnet, but it will attract the south pole of another magnet.
Opposite magnetic poles attract one another much like positively charged atoms attract negatively charged atoms in water molecules. In a water molecule, the two hydrogen atoms align themselves along one side of the oxygen atom, with the result being that the oxygen side has a partial negative charge and the side with the hydrogen atoms has a partial positive charge. Thus when the positive side on one water molecule comes near the negative side of another water molecule, they attract each other and form a bond.
This "bipolar" nature of water molecules gives water its cohesive nature, and thus, its stickiness and clumpability maybe "dropability" is a better term? Looking at water, you might think that it's the most simple thing around.
This is because of the tiny, weak hydrogen bonds which, in their billions, hold water molecules together for small fractions of a second. Water molecules are constantly on the move. If they are moving fast enough they become a gas.
A gas is a physical state of matter where the molecules are far apart and moving very quickly. But, because of the hydrogen bonds, as water molecules come together they stick to one another for a small, but significant amount of time. This slows them down, and holds them closer to one another.
They become a liquid; a different state of matter where the molecules are closer and slower than in a gas. Molecular water, therefore is a liquid at room temperature, a fact that is profoundly significant for all living things on this planet. Everything dissolves in water. Stone, iron, pots, pans, plates, sugar, salt, and coffee beans all dissolve in water. Things which dissolve are called solutes and the liquid in which they dissolve is called a solvent.
The water molecules surround the charged solute; positive hydrogens close to negative charges and negative oxygens close to positive charges on the solute molecule.
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