The Role of Water's Properties in Life: Cohesion, Adhesion, Polarity, and Solubility, Study notes of Biochemistry

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Water and Life

How the properties of water enable life to exist

Cohesion occurs when water molecules stick to each other. Adhesion is when water molecules stick to other surfaces.

Surface Tension- Elastic like force existing on the surface of a liquid, usually minimizes the surface area

Insects can walk on the surface tension of water. Is this an example of cohesion or adhesion?

Ice floats allowing organisms to survive in

winter.

This is because Ice is less dense than water

and water molecules cohere to each other

Large bodies of water change temperature

slower than land:

Coastal temperatures are cooler in the summer and warmer in the winter than inland areas.

Solute- what is being dissolved Solvent- What is doing the dissolving Example- Sugar = solute Water = Solvent Water is the universal solvent

Water is a polar

molecule

How water molecules form polar covalent bonds

Molecules that do not share its electrons evenly are called polar molecules. One end of a polar molecule is slightly negative while the other end is slightly positive.

Polar molecules are like magnets: When two or more polar molecules come into contact, they form a weak attraction called a Hydrogen bond. *remember that opposite charges attract!

Hydrogen bonds can form between

any two polar molecules.

Solid water is less dense than liquid

(so it floats!)

 The cold temperatures freeze the hydrogen bonds in place  Hydrogen bonds are attracted to each other but are still able to move freely

In liquids, water can dissociate to form

hydroxide (OH-) and hydrogen (H+) ions.

Solubility- the ability for a

solute to dissolve in a solvent

Insoluble- when a substance is unable to dissolve in a solvent.