H 2
O — The Amazing Molecule
We can ’ t live without water . We know that , but have you ever thought about how unique the stuff is ?
How many other substances can you think of that you can find in the natural environment in a solid , liquid and vapor form ? It ’ s a trick question . There aren ’ t any . Water never goes away . Earlier we saw the water cycle in action , but it goes beyond that . Water is difficult to destroy no matter how hard you try . You can boil it , freeze it or try to smash it , but it ’ s still water .
Water is a simple molecule — two hydrogen atoms connected to an oxygen atom . You ’ ve undoubtedly seen the formula written as H 2
O . The magnetic attraction of these particles is so strong that the bonds are tough to break .
You might think that those two hydrogen atoms would be on opposite sides of the oxygen , but they ’ re not . They always sit precisely at a 104.5 degree angle , as in the picture . The molecule sort of looks like the ears on that famous mouse character .
The angle of the atoms is important . It gives water special properties . One side of the molecule has a positive electric charge , while the other is negative . This polar charge attracts the molecules to each other .
In addition , the polar charge dictates which substances will readily dissolve in water . When you make lemonade , you put sugar and lemon juice in water . The sugar and juice mix easily , dissolving in the water .
The fact that water dissolves things like sugar and salt , is one key to how your body works . Water transports nutrients and wastes around the inside of your body . When you sweat , the evaporation of the water cools your skin .
However , if we try to mix oil and water , the oil won ’ t dissolve in the water . It will rise to the top . ydrogen
Oil molecules are non-polar .
H e r e ’ s a n o t h e r example : If you get oil on your hands , what happens if you wash with just water ? Not much happens because the water won ’ t dissolve the oil . If you get mud on your hands , it washes off with just water .
Polarity not only helps water dissolve lots of substances , but creates a most unusual phenomena when we freeze it .
Most liquids shrink as they become solids . Water expands , leaving room for air spaces when it freezes . This is why ice floats .
Think about that for a minute . If ice didn ’ t float , we wouldn ’ t be here . Lakes , springs and oceans would freeze solid , instead of having the ice on top . No liquid water , no life .
Sometimes , however , water ’ s ability to dissolve things is a problem .
Let ’ s say we spread fertilizer on a football field to help the grass grow , but we spill some on the driveway .
When it rains or the snow melts , the water dissolves the fertilizer and carries it to the storm drain — you guessed it-we ’ re contributing to runoff pollution . xygen
Here ’ s something else to think about . If we take a wheat seed and place it in a cup of dirt , nothing happens . That seed will sit in there for years , but if we add water , a plant grows . It happens every day . There ’ s nothing else like it . Now that ’ s an amazing molecule .
ydrogen
During a 100-year period , a water molecule spends approximately 98 years in the ocean ,
20 months as ice , two weeks in lakes and less than one week in the atmosphere .
10 Watershed Defenders produced by Colorado Agriculture in the Classroom