Did you know that plants rely on the adhesion of water to survive? In this lesson, you’ll discover what adhesion is, why it occurs, and why it is so important for both plants and people.
What Is Adhesion?
Have ever noticed water droplets sticking to the side of the sink after you have washed your hands? Or drops of dew hanging off the tips of grass in the morning? If so, you’ve witnessed adhesion.Adhesion refers to the tendency of water molecules to be attracted to other substances.
The term comes from the same root as the more common word ”adhere,” as in, ”The glue helped the glitter adhere to the paper.” Both terms have to do with one substance ”sticking” to another.
Water Molecules and Adhesion
As you probably already know, a water molecule consists of two hydrogen atoms bonded with one oxygen atom. These atoms are joined by a covalent bond, meaning that the bonded atoms share electrons.
This is easier to remember when you know that ”covalent” is a Latin term joining co-, meaning ”in common,” and valence which refers to the bondable electrons of an atom.However, the electrons aren’t shared equally. Oxygen is rather greedy and keeps the electrons most of the time. This means that the oxygen molecule has a slight negative charge, and the hydrogen molecules have a slight positive charge. We refer to this phenomenon as polarity, the property of having two polar, or magnetically opposing, ends. The water molecule has charged ”poles” in the same sense that a magnet does.So, just like a magnet, the water molecule sticks to other substances that have polarity, such as the bowl of your sink or a blade of grass.
Water molecules also stick to each other. We call it cohesion when like molecules attract, and we call it adhesion when unlike molecules attract.
Importance of Adhesion in Nature
Plants rely on adhesion to transport water from their roots up to their leaves.
Think of a paper towel rolled up and stuck into a glass to water. The water would slowly climb up the paper towel. Plants do something similar; water climbs up the roots and stems of the plant because of adhesion. This is also known as capillary action, or the tendency of water to be drawn up small tubes (such as the roots of plants) or into narrow openings (such as the spaces between paper towel fibers). Thus, without adhesion and capillary action, plants would not be able to properly distribute their water.
No water means no plants, and without plants, we wouldn’t be here either! Who knew adhesion was so important!
Adhesion refers to the tendency of water molecules to be attracted, or ”stick”, to other substances. This is a result of the covalent bond between the two hydrogen atoms and the one oxygen atom in the water molecule. In a covalent bond, the electrons of the bonded atoms are shared. However, water shows polarity, meaning that the electrons are not shared equally. Thus, one side of the water molecule has a slight positive charge, and the other has a slight negative charge.
Just like a magnet, the poles of the water molecule allow it to stick to other polar substances. Plants rely on adhesion and capillary action to distribute the water from their roots up to their leaves. Capillary action is the tendency of water to be drawn up small tubes or into narrow openings.