Water The elixir of life!!

Water : Common Information... It is colorless, odorless, and tasteless It is the simplest molecule It is made from the 2 most common elements in the universe H O

But Very Unique!!! It is the most studied material on earth. Living things cannot survive without it It is used for many purposes (can you name some?) Our bodies are about 2/3 water.

THE WATER MOLECULE 1 Oxygen atom Bonded to 2 Hydrogen atoms

Sharing electrons… Water molecules have positive and negative atoms. The water molecule is neutral because, opposites attract, so a positively charged atom (hydrogens) will pair up with a negative atom (oxygen). The electrons spend more time around the Oxygen atom.

If oxygen has the electrons around it more often, it will have a slightly negative charge. This means that the hydrogen atoms will have a slightly positive charge.

We call this uneven sharing… Polar molecule – has positive and negative parts (unequal sharing of electrons) (+) charge ---- ---- (-) charge (+) charge -----

Simply put… Polar Molecule: A molecule with an uneven charge

POLAR VS NON POLAR Polar = Hydrophilic (water loving) Non Polar = Hydrophobic (water fearing)

WATER: THE UNIVERSAL SOLVENT Almost everything will dissolve in water!!!! Solvent - something that dissolves another material Solute - the material that dissolves SOLVENT + SOLUTE = SOLUTION

WATER: THE UNIVERSAL SOLVENT BEFORE ADDING WATER AFTER ADDING WATER

WATER: THE UNIVERSAL SOLVENT Because water is polar, anything else that has areas of charge will be able to dissolve in it.

WATER: THE UNIVERSAL SOLVENT Why might this property be important to living things? It allows most substances to dissolve in water- our blood is mostly water, so things like sugars and gasses can dissolve in it.

More about water When many water molecules are placed in the same area, the + and -- sides will attract. This forms bonds between neighboring molecules called hydrogen bonds.

THIS CAUSES WATER MOLECULES TO STICK TO ONE ANOTHER!!!! HYDROGEN BONDING Hydrogen bonding – when the positive ends of one molecule are attracted to the negative end of another molecule THIS CAUSES WATER MOLECULES TO STICK TO ONE ANOTHER!!!! ---- ---- ---- ----

Hydrogen bonds cause water to “stick” to itself. This property is called cohesion.

This force also causes something called adhesion molecules are attracted to others and they try to squish together in the smallest possible space.

In other words… Water is sticky!! Water can stick to other water molecules = cohesion Water can stick to other molecules = adhesion

CAPILLARY ACTION Capillary Action – the tendency of a liquid substance to move a long a solid substance due to adhesion (to stick to something)

Capillary Action This helps Trees and tall plants get the water they need Blood flow back up the veins in your legs

SURFACE TENSION Water molecules under the surface are stuck to each other Water molecules at the surface line don’t have anyone to “cling” to so they turn inward This causes the top layer of molecules to act like a thin membrane

Surface Tension pictures

Why a belly flop hurts! You’re breaking the Surface Tension with your Body!!

More about water… Another property of water is the fact that as it freezes, it expands. This is important because ice floats.

Because of hydrogen bonds, water is very effective at maintaining a stable temperature

This helps maintain living systems because living things are made of about 70% water. Distribution of Weight in the Human Body

Water Fact and Fiction Water has some very interesting properties. See if you can separate the fact from the fiction!! Take out a sheet of notebook paper Number your paper from 1 – 10 Write down if you think the following statements about water are true or false

1. Water contracts (gets smaller) when it freezes. 2. Water has high surface tension. 3. Condensation is water coming out of the air. 4. More things can be dissolved in acid than in water. 5. Rainwater is the purest form of water.

7. Sea water is slightly more basic than fresh water. 6. If you evaporate an 8 inch tall glass of water from the salt lake (about 20% salinity) you will end up with about 1 inch of salt. 7. Sea water is slightly more basic than fresh water. 8. Tap water is slightly more acidic than distilled water. 9. Raindrops are tear shaped. 10. Water boils more quickly in Denver, CO than here in Baltimore, MD.

1. Water contracts (gets smaller) when it freezes. FALSE 2. Water has high surface tension. TRUE 3. Condensation is water coming out of the air. 4. More things can be dissolved in acid than in water. 5. Rainwater is the purest form of water.

7. Sea water is slightly more basic than fresh water. 6. If you evaporate an 8 inch tall glass of water from the salt lake (about 20% salinity) you will end up with about 1 inch of salt. TRUE 7. Sea water is slightly more basic than fresh water. 8. Tap water is slightly more acidic than distilled water. 9. Raindrops are tear shaped. FALSE 10. Water boils more quickly in Denver, CO than here in Baltimore, MD.