Re: water is colourless and tasteless, why?

Date: Sat May 5 11:37:20 2001
Posted By: Lynn Bry, MD/PhD, Department of Pathology, Brigham & Women's Hospital, Harvard Medical School
Area of science: Chemistry
ID: 989051228.Ch

Message:

Hi Syed - You have asked two interesting questions.

For the first one, I'll refer you to some files in our archives that address why water appears colorless:

Does pure water have a color?
Why can you see a perfectly transparent piece of glass in water?
How do atoms of an object absorb or reflect photons/light to give color?: A very detailed response, covering more than just transparency of water.

Concerning why water has no taste, you might rephrase it as, "why water has no taste to us," for taste represents a perception on our part. We perceive tastes through the taste buds on our tongue. The human tongue can perceive 4-5 different kinds of tastes: salty, sweet, sour, bitter, and more recently discovered 5th receptor that detects monosodium glutamate (MSG).

Each of these "tastes" can be defined in terms of small molecules that interact with the taste receptors. For instance, you perceive the sugars sucrose or fructose as "sweet", sodium chloride, potassium chloride, and other forms of salts as "salty." These different forms of perception play a number of roles, including:

To help us identify foods with nutrients we need.
To help us identify foodstuffs that are spoiled or that may be toxic.

Think of how normal milk tastes versus the sensation your tongue experiences if you take a gulp of spoiled milk! Which one are you going to swallow?

Thus, returning to water - pure H₂O simply contains nothing that triggers our taste receptors, and is thus perceived as tasteless.

For more information, try querying our archives with terms such as taste receptors or umami

Hope this helps..

-L. Bry, MadSci Admin

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