1. What makes up ¾ of the Earth’s surface and ¾ of your body weight?

2. Water is Essential for Life! Life is thought to have evolved in water Water is inorganic and provides no energy to organisms Water provides the environment where most metabolic reactions happen: ~70% of the weight of your body is water! Water is used for:  Waste excretion (urine, sweat)  Temperature regulation (sweat)  Maintaining the pH (level of acidity) and concentration of body fluids

3. Water’s Polarity – Oxygen is an Electron Hog!!! or: a very electronegative element – why? Visualizing Properties of Water  http://glencoe.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078759864/383915/CH06_Prop erties_of_Water_103006.swf::Visualizing Properties of Water A hydrogen bond is a weak interaction involving a hydrogen atom and certain atoms: O, N.

4. Hydrogen bonds between water molecules hold them together and give water its special properties.

5. Water Properties Polarity = unequal distribution of charges  water dissolves other polar or hydrophilic substances Cohesiveness & Adhesiveness  water molecules “stick” together due to hydrogen bonds & stick to other materials High Specific Heat  water absorbs a relatively large amount of heat and “holds on to it”  temperature moderator in climate Expands while freezing  ice is less dense than water and floats on it Neutral pH  water does not react with biological molecules; neutral point on pH scale (7)

6. Cohesiveness - Examples Surface Tension Water Transport in plants

7. Why do white bears dissolve in water? Because they’re Polar!

8. A solution is a mixture in which one substance is dissolved in another. A solvent is a substance in which another substance is dissolved. A solute is the substance that is dissolved in the solvent Concentration = amount solute / amount solvent (ratio, relative amounts) “Like dissolves like” Polar solvents dissolves polar/hydrophilic solute Nonpolar solvents dissolve nonpolar/hydrophobic solutes Sugar and salt dissolve in water. What can you infer about sugar and salt based on this? Water is termed “the universal solvent” because it dissolves most substances in nature. Food coloring dissolved in water forms a homogenous mixture. Water and Solutions

9. Water is the “Universal” Solvent Water Molecule Water acts as a ‘magnet’ & pulls apart polar compounds Ex.: ionic compound dissolving in water Is the ionic compound hydrophilic or hydrophobic?

10. Water Molecules Interacting with Charged Particles (a)

11. What is the Solute? What is the Solvent? What is the definition of a Solution? What determines the Solution’s Concentration? Sugar Cube Liquid in cup Solute dissolved in a solvent The ratio of Solute to Solvent Sugar Cubes

12. Why should you discuss all your problems with a chemist instead of Dr. Phil? Because Chemists have SOLUTIONS!

13. Concentration of a Solution What can you do to increase the concentration of a solution? ..increase solute or decrease solvent. What can you do to decrease the concentration of a solution? ..decrease solute or increase solvent. What will happen to the concentration of your body fluids if you (or any organism) becomes dehydrated?  It will increase; you need to drink water to restore homeostasis. What will happen if you have too much water in your body?  Body fluids will be too dilute; your kidneys will excrete the excess water in urine to keep homeostasis. How will this affect metabolic reactions? Think homeostasis.  Metabolic reactions cannot happen properly if fluids are too concentrated or too dilute.

14. Which solution is more concentrated? A or B? A or C? B or C? AB C

15. Water Ionizes / Dissociates (slightly) into Positive and Negative Ions: H 2 0  H + + OH - Which is the cation / anion? Water is neither acidic nor basic – its pH is neutral. Hydronium IonHydroxide Ion

16.  Acids and bases are substances that give off certain ions (charged atoms).  Acids and bases are reactive: they can interfere with metabolic reactions and react with body tissues. pH, Acids and Bases

17. On the pH scale, water is used as a comparison to determine acid and base Each unit in the pH scale = 10X concentration of ions Ex.: pH 3 is 10 x more acidic than pH 4 pH 8 is 10x more basic than pH 7 The measure of concentration of H + (hydrogen ions) in a solution is called pH.

18. Buffers are substances that can react with acids or bases to keep the pH within a particular range  HOMEOSTASIS! Organisms have buffers in their body fluids. pH and Buffers