Source: Georgia State University. Looking at water, you might think that it's the most simple thing around. Pure water is practically colorless, odorless, and tasteless. But it's not at all simple and plain and it is vital for all life on Earth. Where there is water there is life, and where water is scarce, life has to struggle or just "throw in the towel.
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.
The cohesive forces between liquid molecules are. Take a look at. Skip to main content. Search Search. Water Science School. Surface Tension and Water. Water Properties Information by Topic Learn more. Science Center Objects Overview Related Science Publications Multimedia Surface tension in water might be good at performing tricks, such as being able to float a paper clip on its surface, but surface tension performs many more duties that are vitally important to the environment and people.
Below are other science topics associated with surface tension and water properties. Date published: October 22, Filter Total Items: 1. Both of these phenomena are due to surface tension. In a sample of water, there are two types of molecules. Those that are on the outside, exterior, and those that are on the inside, interior.
The interior molecules are attracted to all the molecules around them, while the exterior molecules are attracted to only the other surface molecules and to those below the surface. This makes it so that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. Because of this, the molecules try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. This is what creates what is referred to as surface tension.
The water molecules attract one another due to the water's polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen cause water to "stick" together. This is why there is surface tension and takes a certain amount of energy to break these intermolecular bonds. The stronger the cohesive force, the stronger the surface tension.
The water molecule has two hydrogen atoms bond to an oxygen atom through covalent bonding. Due to the high electronegativity of oxygen, it will have a large portion of the negative charge on its side whereas hydrogen will be more positively charged. This causes an electrostatic attraction between the hydrogen atom in one molecule and the oxygen atom in another.
Formed bonds are called hydrogen bonds which lead to strong cohesive forces between the water molecules and high surface tension of water. As mentioned at the beginning of the blog, this also explains why mercury has so high surface tension. As mercury is a metal, the bonds between the molecules are metal bonds that are much stronger than the hydrogen bonds leading to very high cohesive forces and high surface tension.
A wetting agent is a surface-active molecule used to reduce the surface tension of water. Or with optical tensiometer using the pendant drop method. Surface tension of blood is an important characteristic when protective materials are being evaluated.
A basic requirement of any coating is that it should form a uniform, defect-free surface. Have you ever overfilled your glass of water so that the water level is higher than the glass and still the water remains in the glass? This seemingly gravity-defying observation indicates there is a force that wants to keep the liquid together. This force is called the surface tension. Imagine the interface between a liquid and a gas.
Most of the molecules in both phases are in the bulk but some of the molecules are at the interface facing the other phase. The molecules in the bulk interact similarly with all the molecules surrounding them — there is a similar pull to all directions resulting in zero net force.
On the contrary, the molecules at the interface experience a stronger pull towards the bulk of their own phase. The net force, which effectively aims to keep the liquid together, is called surface tension.
Mathematically, surface tension is the force exhibited by the intermolecular forces divided by the length of the contact line between the phases.
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