Water and its unique properties

Main Concepts Polarity and Hydrogen Bonding Cohesion & Surface Tension Adhesion Solvent of life Hydrophilic & Hydrophobic Like dissolves like

Polarity: results in a slightly negative charge on O, and + on H http://images.google.com/imgres?imgurl=http://rst.gsfc.nasa.gov/Sect20/water_molecules_con_c_la_784.jpg&imgrefurl=http://rst.gsfc.nasa.gov/Sect20/A12.html&usg=__4nL5_tMqo5tEsLFcKvfpzxREfEA=&h=382&w=557&sz=34&hl=en&start=16&um=1&itbs=1&tbnid=Q7lopDUrOZQmoM:&tbnh=91&tbnw=133&prev=/images%3Fq%3Dwater%2Bmolecules%2Bare%2Bpolar%2Bwith%2Bthe%26hl%3Den%26rlz%3D1T4ADSA_enUS359US360%26sa%3DN%26um%3D1

Polarity allows hydrogen bonding Each water molecule can form 4 hydrogen bonds. These create its unique properties. This intermolecular force is weaker than a covalent or ionic bond. Hydrogen bonds are 1/12 as strong as a covalent bond. H bonds are forming and breaking constantly . Each H bond lasts only a few trillionths of a second. At any time there are many H bonds making water one of the more structured liquids. http://images.google.com/imgres?imgurl=http://wpcontent.answers.com/wikipedia/commons/thumb/f/f9/3D_model_hydrogen_bonds_in_water.jpg/250px-3D_model_hydrogen_bonds_in_water.jpg&imgrefurl=http://www.answers.com/topic/hydrogen-bond&usg=__2rUTTXCUfq_P4PrjsSpk_bKHpK0=&h=248&w=250&sz=10&hl=en&start=19&um=1&itbs=1&tbnid=L8auZz3YifI0iM:&tbnh=110&tbnw=111&prev=/images%3Fq%3Dice%2Band%2Bhydrogen%2Bbonds%26hl%3Den%26rlz%3D1T4ADSA_enUS359US360%26sa%3DN%26um%3D1

Cohesion and Adhesion Cohesion is the attraction between molecules of the same substance. Examples: pull of water through plants against gravity from the roots to the leaves. Adhesion is the clinging of one type of substance to a different substance. Example: Allows water to adhere to the walls of a plant to counteract the force of gravity. Hydrogen

Organisms depend on cohesion

Cohesion relates to surface tension Surface tension is a measure of how difficult it is to stretch or break the surface of a liquid. Cohesion between the water molecules pulling down and across the surface creates the film.

Surfactant-something that breaks down the surface tension of water Disrupts hydrogen bonds. Breaks surface tension like the popping of a balloon. Boat moves with the moving water molecules. Soap create micelles to get rid of dirt too. the water molecules in front of the boat separate with more force than the molecules near the soap at the back of the boat. Adding soap disrupts the arrangement of the water molecules and breaks the skin, making the boat go forward. The attraction between water particles at the water's surface produces surface tension. This gives the surface a skin-like quality. Think of this thin skin-like quality like a balloon. Adding liquid soap is like popping the balloon. You break the surface tension; the thin "skin" breaks and pulls away to the sides. If there's something floating on these water particles, like the boat, it goes along for the ride.

Boiling point is higher than it would be due to hydrogen bonds. Why would that be important to living things? Water stabilizes air temperatures by absorbing and releasing heat. Water serves as a heat bank. It can absorb or release a large amount of heat with only small changes in its temperature. Example: Reason costal regions are temperate. Heat is a measure of the total quantity of kinetic energy (energy of motion) due to molecular motion. Temperature measures the intensity of heat due to the average kinetic energy of the molecules. When the average speed of molecules increases, a thermometer records this as a rise in temperature.

Ice floats because of hydrogen bonds. Liquid water has hydrogen bonds constantly breaking and reforming. In ice hydrogen bonds are stable and holds molecules a but farther apart. The molecules are farther apart which makes ice less dense. D = Mass/ Volume. Larger volume. http://www.ifm.liu.se/compchem/research/pics/iceIh-Fig1a.jpg

Water is the solvent of life Solute and solvents. Like will dissolve like. Water polar – oil non polar. Water and oil don’t mix. Water will also dissolve ionic compounds due to the charges on the water molecule. Polystyrene (made of oil) will not dissolve in water but will dissolve in oil. What does that say about acetone? Oxygen regions of water negatively charged and attracted to sodium cations. (+) Hydrogen attached to chloride anions (-) Acetone is non polar.

Conductivity Distilled water - only H2O molecules Tap water – impurities (minerals, chlorine) Sugar – covalent Salt – ionic Glows if the conduction is consistent Blinks if the conduction is inconsistent TAKE HOME LESSON – RAIN WATER AND TAP WATER CONDUCT! DO NOT MIX WITH ELECTRICITY!!!!!!!!!!!!!!!