Biology Basics for Middle School Students

What About Water?

We all grew up hearing how important water was, but did anyone actually know how important it truly was. Water is around us all the time and it even makes up 70% of your body. Water is not only important to humans, but to plants and animals as well. Water is made from a covalent bond (the formation of two nonmetals bonding) of hydrogen atoms and oxygen atoms. Knowing what water is made up of helps understand how water is so versatile.

Picture showing human with a bottle of water
Human Body Drink Water by Mohamed Hassan, via Pixabay
Water Molecule Illustration
MsKDinh, CC BY-SA 4.0, via Wikimedia Commons

The oxygen atoms in water are bigger than the hydrogen atoms so more substances bond to it. Since opposites attract, hydrogen is positive that bonds with a negative oxygen. Oxygen and hydrogen can bond with other molecules along and similar molecules, which is important in the first property of water that will be discussed.

Since hydrogen is positive it bonds with negative molecules, oxygen is the opposite. Oxygen is bigger than hydrogen so its bonds are stronger. Hydrogen can bond with itself which makes water able to go against gravity- this is called cohesion. Cohesion gives water the ability to have a very strong surface that’s hard to break so some bugs can crawl on it! Cohesion has a property that does the opposite of it- adhesion. Adhesion has water going up against gravity, but adhesion is when water bonds with other molecules.

Transpiration of water in xylem is the movement of water in plant cells. It is an example of cohesion and adhesion.

FeltyRacketeer6, CC BY-SA 4.0, via Wikimedia Commons
Picture of Beach and Water
Beach, Sand, Water, Waves, Free for commercial use, DMCA, via pxfuel.com

The next property is specific heat. Water serves as a regulator of temperature for all forms of life. Specific heat is defined as the amount of heat needed to raise the temperature by 1 degree. Water’s high specific heat allows for the sun to be constantly beating on the surface and the heat of water to only increase by about a few degrees. The same applies at night. This allows the fish and sea life not to get too hot during the warm summer days as well as keeps temperatures low on land.

The next property that is special to water is how it is a universal solvent. Water usually dissolves most solutes it comes in contact with. This is because of how water is structured as a polar molecule. While talking about how water is a solvent, we can talk about molecules that love water and ones that hate water. Water loving molecules are called hydrophilic and molecules that hate water are hydrophobic.

Close-up of a drop of water on surface

Close-up of Drop on Surface by Quang Nguyen Vinh, via Pexels
Picture of Men Ice Fishing
Men Sitting on Coolers Near a Tent Fishing on Ice by Tima Miroshnichenko, via Pexels

The last property of water is its density as a solid. Picture a lake in the winter with a layer of ice on top of it. What you see is a solid floating on top of a liquid. Water is less dense as ice than it is as a liquid. Less dense materials float on top of more dense materials. When water freezes it becomes crystalized with its molecules equally distant from each other and less dense than liquid water. That is why ice floats on top of the lake.

Handout

Strengthen your understanding of the importance of water and it’s properties by matching the correct pairs from each column. This exercise will show you how much you’ve learned and where are your knowledge gaps about water’s properties.

Pronunciation Key and Vocabulary List

Cohesion-koh-hee-zhuhn Objects sticking to the same objects

Adhesion-ad-hee-zhuhn Objects bonding to other objects

Specific Heat-

Covalent– The sharing of electrons between atoms

Hydrogen– Colorless gas that bonds with oxygen

Oxygen– Gaseous element