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Water: The Molecule of Life

Water is made of 1 oxygen atom (O) and 2 hydrogen atoms (H2). These atoms are held togather with covalent bonds: they share electrons in an effort to fill thier outer electron shells.

Water molecules are POLAR, which means that the electrons are shared uneaqually between the

atoms, making the oxygen side negatively charged, and the hydrogen side positive.

This polarity allows water molecules to hydrogen bond to one another, the oxygen side of one molecule is weakly attracted to the hydrogens of another due to their weak charges

Water's Best Qualities!

COHESION

Formation and reformation of hydrogen bonds hold liquid water together

This water strider can run over the surface of water due to water's surface tension, which is made possible by cohesion. Water molecules on the surface hydrogen bond to form a kind of invisible skin that is reletivly difficult to break.

Cohesion and adhesion, which is when water molecules hydrogen bond with other molecules, are also responsible for the transport of water against gravity in plants.

As water evaporates out through the leaves, the water chain, made by cohesion, pulls on all the molecules down through the tree.

MODERATION OF TEMPERATURE

Water has a high specific heat, which means it takes alot of heat to raise 1g of water 1 degree celsius.

This means that water can absorb large amouts of heat without changing temperature dramatically

COMPARATIVE DENSITIES

Water is less dense as solid ice than as a liquid. It expands when it freezes, because each molecule binds to 3 others, keeping all molecules a certain distance from one another.

That means that ice floats. The ice insulates lower layers of water, perventing large bodies of water from freezing completely

VERSITILE SOLVENT

Water, because of it's polarity, is a versitile solvent. It easily dissolves polar molecules, or even non-polar molecules with polar sections.

The shell that forms around each dissolved ion is called the hydration shell

All of water's best qualities come from its polarity!

Acidic and Basic Conditions

Every molecule has a molecular mass, which is the sum of the masses of all the atoms in the molecule

A mole is a chemical mass unit, defined as 6.02X10^-23 molecules. The mass of a mole of a particular substance is equal to the molecular mass of the molecule

So the molecular mass of salt (Na Cl), for example, would be the atomic mass of Sodium, which is 11 atomic mass units, plus the mass of Chlorine, which is 17 amu, which makes the atomic mass of NaCl 28

Therefore, 1 mole of NaCl is 28 grams. If you wanted to make a 1 molar solution of NaCl, you would measure out 28 grams, and mix it with water, until you had the desired volume of solution.

The molarity of a solution is the number of moles of solute per litre of solution

A hydrogen ion [H+] is a positively charged ion, composed of a hydrogen atom, minus one electron (which is simply a proton)

An hydoxide ion [OH-] is composed of an O and H atom and has a negative charge

Buffers are substances that minimize changes in [H+] and [OH-] concentration in a solution. A buffer works by accepting H+ ions when they're in excess, and donating them when they're depleted. Buffers are used to maintain a stable pH in biological fluids, which is necessary for the optimal function of protiens, as mentioned in the video.

The buffer in human blood is Bicarbonate (HCO3-)

Acid Precipitation is rain, snow, or fog with a pH of less than 5.6, which is the normal pH for precipitation

It's formed by sulfur and nitrogen oxides in the air, which form acidic compounds with water.

These oxides are a biproduct of burning fossil fuels, like gas from cars or coal-burning factories.

Acid rain can damage life in lakes and streams, and also wash away important nutrients from soil on land and making the soil more acidic...

hydrogen and

Which is not good news for forests that expirience acid rain.

oxygen

Water is what makes life possible on Earth, which is why we look for it on other planets!

THE END!

Water also has a high heat of vaporization, which is, it takes alot of heat to evaporate water. Evaporative cooling also plays a role in this effect. When the top layer of water molecules evaporate, the layer underneath is much cooler.

Since most of the Earth's surface is covered with water, the oceans can absorb most of the sun's energy, keeping the planet reletively temperate.

An hydrophillic subtance has an affinity for water, like the salt crystal. An hydrophobic subtance has an aversion to water, like an oil droplet.

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