Water: My Favorite Molecule

Ronald R. Martin

Department of Chemistry

University of Western Ontario

Let’s Meet Two Elements

• Introducing Hydrogen (H)

• The lightest element

• But 70% of the mass of the known universe.

Hydrogen In Space

Let’s Meet Two Elements

• Introducing Hydrogen (H)

• The lightest element

• But 70% of the mass of the known universe.

• And Oxygen (O) or as it occurs in our Atmosphere O2

• About 20 % of the air we breathe is oxygen

Atoms and Molecules

• Put atoms together and you get molecules, some very big, some very small

Molecules can be very small, such as H2 (2 amu);

or they can be huge, like proteins (> 10,000 amu)

The protein cytochrome c consists of thousands of atoms, all linked by covalent bonds. Its mass is 12,360 amu

Putting Hydrogen and Oxygen Together Yields Water

HOH or H2O

Density and phase1000 kg·m−3, liquid (4 °C)

917 kg·m−3, solid

Melting point 0 °C, 32 °F (273.15 K)[2]

Boiling point 100 °C, 212 °F (373.15 K)[2]

Physical Properties of Water

What’s So Amazing About Water

• Lots, but most important to us: You Can’t Have Life Without IT!

• About 70% of the Human Body is Water

Water in Outer Space

Water is a Major Component of Comets

Water Has been Found

on the Moon,

on the planets Mercury, Mars, and Neptune, on the dwarf planet Pluto,

on satellites of planets, such as Triton and Europa.

The liquid form of water is only known to occur on Earth

strong evidence suggests that it is present just under the surface of Saturn's moon Enceladus.

Earth From SpaceIt looks as if there’s lots of water

The bad news, there isn’t !

Some Facts About Water On Earth

• Most of it is too salty to drink, or to be used for agriculture

• Much of the fresh water is frozen as ice

Much of Our Water is Frozen

Some Facts About Water On Earth

• Most of it is too salty to drink, or to be used for agriculture

• Much of the fresh water is frozen as ice

• Some countries have a lot

Some Facts About Water On Earth

• Most of it is too salty to drink, or to be used for agriculture

• Much of the fresh water is frozen as ice

• Some countries have a lot

• Some have very little, in fact 18 countries now have insufficient water for their needs, the economic and social consequences are immense.

Waterless Northern India

Let’s talk about Australia

• 80 % of all its agriculture is sustained by the Murray-Darling watershed.

The Problem With The Murray-Darling

• Average peak flow per month: 2,000,000,000,000 liters

• Peak flow 2006 per month: 250,000,000,000

• Peak flow 2007 per month: 100,000,000,000

• Flow is now 1/20 peak average.

What The Darling Looks Like Today

Reasons?

• Australia grows both cotton and rice at the sources of the Murray and the Darling

• Downstream demand increases as populations grow

• Control is fragmented, divided between the state and federal governments and is hopelessly out of date

• But there is a much bigger and more important reason!

SO

• We know there is limited useful water on the surface of the earth.

• We know water use is increasing exponentially.• We know we are changing the climate of the

planet in ways that will adversely affect water supply and distribution.

• It’s one of our most important molecules.• It’s time to start doing something to protect the

resource.

Thanks

Have a Drink

Of Water