chapter 3. it’s pretty important… life probably evolved in water cells are 70% to 90% water...

Chapter 3

It’s pretty important…Life probably evolved in waterCells are 70% to 90% waterWater covers ¾ of the earth’s surfaceIt naturally exists in all 3 states

HOW MANY THINGS CAN YOU SAY ALL THAT ABOUT????

Water is polar, which is pretty cool!It results from the polar covalent bond between the

elements, hydrogen and oxygen. Each H2O molecule can bond with 4 other water

molecules due to its unequal charge.

What type of bond is that? Hydrogen Bond

1 2

3

4

Properties of polarity - CohesionCOHESION – the ability of H2O molecules to

stick together (their attraction). Also, part of the reason for capillary action.

Adhesion – the ability to adhere to another surface. (kind of like Van der Waals interactions)

Surface Tension – the measure of how hard it is to break the surface of water. (like a water skimmer, or drops of water on a penny)

Properties of polarity - TemperatureHigh Specific Heat – the amount of energy it

takes to raise the temp. by 1o Celsius. Water is 1cal/g/oC

Why don’t oceans vary in temperature that much?

Evaporative Cooling – since water has a high heat of vaporization, once water leaves the surface, the surface cools down.

What homeostatic mechanism does this for us?

Sweating Cools us down!!!

Ice Floats!!!!So what, big deal, right? …….. WRONG!!!!Water is less dense as a solid 0oC;

it is most dense at 4oC! HUH?

Well at 40 it has contracted the most, then from 4o to 0o it begins expanding and is less dense, hence the floating.

This acts as insulation to prevent freezing of deep bodies of water!!!

Universal SolventSolvent – water is the universal solvent since

ionic and polar compounds both dissolve in it. (hydrophilic)Hydrophbic compounds do not dissolve in water,

ex. lipids

Solute – the stuff dissolved in a solventSolution – solvent +soluteAqueous Solution – a solution in which water

is the solvent.Express in Molarity. See next slide…

…..Measure out a mole of sucrose.Calculate the molecular weight of C12H22O11

C = 12 dal, H = 1 dal, O = 16 dal x12 x22 x11_________________________________________

144 dal 22dal 176dal = 342 dal or 342gNow to make a 1M sucrose sol’n, weight out 342 g

of sucrose and add water up to 1L.

TA DAA! (this is useful for AP Lab #1 Osmosis and Diffusion)

Don’t forget pHWater dissociates into H+ and OH- ions!Acids 0 – >7Bases <7 - 14Distilled water is neutral, is tap water???Buffers, ex. Carbonic acid, HCl, NaOH

Science, Technology, and SocietyAcid Rain has been recorded as low as 1.5 in

West Virgina.Result of Sulfur Dioxide and nitrogen oxides

react with water in the air to form acids.Where do the sulfurs and nitrogen oxides

come from?What do they do to the Environment?