Which is stronger cohesion or adhesion

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. 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. A meniscus is a curve in the surface of a molecular substance water, of course when it touches another material.

With water, you can think of it as when water sticks to the inside of a glass. 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. Find out all about surface tension and water here. Does water still feel wet in outer space? Does it float or does it fall?

With a little help from our friends at NASA we will help you understand exactly how water behaves in outer space. Continue reading to learn more. How much do you know about water properties? Plants and trees couldn't thrive without capillary action.

The density of oil is less than that of water, yet a loaded oil tanker sits lower in the water than an empty one. Birds such as ducks, geese, and swans have greater densities than water, yet they are able to sit on its surface.

Explain this ability, noting that water does not wet their feathers and that they cannot sit on soapy water. Water beads up on an oily sunbather, but not on her neighbor, whose skin is not oiled. Explain in terms of cohesive and adhesive forces.

What effect does capillary action have on the reading of a manometer with uniform diameter? Explain your answer. Pressure between the inside chest wall and the outside of the lungs normally remains negative. Explain how pressure inside the lungs can become positive to cause exhalation without muscle action. What is the pressure inside an alveolus having a radius of 2. You may assume the pressure is the same as that created by a spherical bubble.

Assuming the alveolus acts like a spherical bubble, what is the surface tension of the fluid? You may need to extrapolate between values in Table 1. What is the gauge pressure in millimeters of mercury inside a soap bubble 0.

Calculate the force on the slide wire in Figure 3 shown again below if it is 3. Figure 9 a shown again below shows the effect of tube radius on the height to which capillary action can raise a fluid.

We stated in Example 2 above that a xylem tube is of radius 2. What fluid is in the device shown in Figure 3 shown again below if the force is 3. If the gauge pressure inside a rubber balloon with a Calculate the gauge pressures inside 2. Which liquid forms the most stable bubbles, neglecting any effects of evaporation?

Suppose water is raised by capillary action to a height of 5. Is this value consistent with that for most organic liquids? When two soap bubbles touch, the larger is inflated by the smaller until they form a single bubble. Calculate the ratio of the heights to which water and mercury are raised by capillary action in the same glass tube.

What is the ratio of heights to which ethyl alcohol and water are raised by capillary action in the same glass tube? Alcohol forms the most stable bubble, since the absolute pressure inside is closest to atmospheric pressure.

Skip to main content. Fluid Statics. Search for:. Define surface tension. Understand capillary action. Cohesion and Adhesion in Liquids. Adhesive Forces Attractive forces between molecules of different types are called adhesive forces. Surface Tension Cohesive forces between molecules cause the surface of a liquid to contract to the smallest possible surface area. Making Connections: Surface Tension Forces between atoms and molecules underlie the macroscopic effect called surface tension.

These attractive forces pull the molecules closer together and tend to minimize the surface area. This is another example of a submicroscopic explanation for a macroscopic phenomenon. Table 1. Example 1. In order for this activity to work, the needle needs to be very clean as even the oil from your fingers can be sufficient to affect the surface properties of the needle. Pull the brush out and notice that for a short while, the bristles will stick together.

The surface tension of the water surrounding the bristles is sufficient to hold the bristles together. As the bristles dry out, the surface tension effect dissipates. Adhesion is the reason behind water sticking to different surfaces. It also makes water spread over a surface when poured. Adhesion is related to an electrostatic force or mechanical force which is often found to be strong.

This force gives the liquid its sticking property. Adhesion force needs to be sometimes stronger or sometimes even weaker depending on the activity to be performed. Cohesion is responsible for the spherical and clumpy structure of water. In other words, water molecules like hydrogen and oxygen are held by cohesive force making water stable. Cohesion is related to weak Van der walls forces and surface tension. Cohesive force is the reason why we are able to store water in containers or else water molecules would not be attracted to each other.

Adhesion is an attractive force helping substances to stick to one another. We can observe various activities in nature which proofs the existence of adhesion. When the adhesive force of the liquid to the wall is stronger than the cohesive force of the liquid, the liquid is more attracted to the wall than its neighbors, causing the upward concavity.

In agitated glasses of wine, droplets of wine seemingly "float" above the meniscus of the liquid and form "tears. Alcohol is more volatile than water. As a result, "evaporation of alcohol produces a surface tension gradient driving a thin film up along the side of a wine glass" Adamson. This process is called the "solutal Marangoni effect. The "tears" form from the cohesive forces within the water holding it together.

It is important to note that the surface tension gradient is "the driving force for the motion of the liquid" Gugliotti , but the actual formation of the tears is a result of cohesive and adhesive forces. Adhesive and Cohesive Forces The term "cohesive forces" is a generic term for the collective intermolecular forces e.

Macroscopic Effects of Cohesive and Adhesive Forces When a liquid is placed on a smooth surface, the relative strengths of the cohesive and adhesive forces acting on that liquid determine the shape it will take and whether or not it will wet the surface. Case I: The Meniscus The meniscus is the curvature of a liquid's surface within a container, such as a graduated cylinder.

Case II: Tears of Wine In agitated glasses of wine, droplets of wine seemingly "float" above the meniscus of the liquid and form "tears. The "tears of wine" are observed as a ring of clear liquid, near the top of a glass of wine, from which droplets continuously form and drop back into the wine. It is most readily observed in a wine which has a high alcohol content. Problems Name two examples where the cohesive force dominates over the adhesive force and vice versa.