Water Lab  PURPOSE: To observe how water behaves and infer how life “takes advantage” of those behaviors/properties.  You will perform 8 mini-experiments, carefully OBSERVE what water does, thoughtfully INFER the value to life and RECORD your responses  Get Role cards from purple box. Person number 1 is the Materials person (blue)

Water Lab  PURPOSE: To observe how water behaves and infer how life “takes advantage” of those behaviors/properties.  1. Capillary Action…  2. Surface Tension…  3. Oil, Alcohol & Water…  4. Wetting (wax slide, clean slide)…  5. Density…  6. Freezing Point…  7. Imbibition (definition?)…  8. Solutions…

Lab Conclusions: What’s Up with WATER? Or…What’s the big deal about a little H 2 O? When you are done with your lab,answer this in your journal. Build 3 or more water molecules to model how they interact: 1. Which atom in the water molecule will hold more tightly to the shared electrons? Oxygen or hydrogen? Why? 2. Will that give the atom a slightly more negative or positive charge? What happens to the other atom’s charge? 3. Sketch two water molecules showing the way they would orient themselves due one part of the molecule being slightly negative and one part being slightly positive. (Remember: opposites attract).

Structure of Water  Water molecules are made of oxygen and hydrogen ATOMS. oxygen and hydrogen ATOMS.  Covalent bond are 2 shared electrons 2 shared electrons  Oxygen keeps the shared electrons (-) more than hydrogen, so…  oxygen side of the water molecule is like the negative end of magnet,  the hydrogen side is positive. Sketch This! (-) (+) When the electrons in the covalent bond are shared unequally, this is a POLAR COVALENT BOND

Structure of Water  So… water molecules will act like little magnets and STICK TO EACH OTHER. This creates a WEAK but PLENTIFUL bond called a HYDROGEN BOND: attraction between (-) Oxygen on one molecule and the (+) Hydrogen on a different molecule Draw the water molecules and show the hydrogen bonds

KEY CHARACTERISTIC of WATER:  So the most important thing about water is that it is  POLAR!!!!!  (meaning like a magnet)

Because Water is Polar Consequence #1 Water Clings to other molecules COHESION Water clings to water Water clings to waterADHESION Clings to other molecules called: Clings to other molecules called: What’s happening here? Surface tension

Because Water is Polar: Consequence #1: Clings to other molecules  Where did you see BOTH cohesion and adhesion in the lab? Capillary tubes Capillary tubes  So…the consequences for life…?  Water moves up tree

Polar Consequences #2 Moderation of Temperature  High Specific Heat is the amount of energy needed to raise one gram of the substance one degree Celcius Increased heat = molecules move faster (more kinetic energy) Increased heat = molecules move faster (more kinetic energy) But, water has lots of hydrogen (H) bonds, so to move faster it needs to …break Hydrogen Bonds! But, water has lots of hydrogen (H) bonds, so to move faster it needs to …break Hydrogen Bonds! Water can absorb a LOT of energy Water can absorb a LOT of energy before it heats up.

Because Water is Polar :Consequence #2: High Specific Heat  High Specific Heat Consequence:  Organisms contain lots of water so… they are resistant to temperature changes

Because Water is Polar Consequence #2 it has a High Specific Heat  Which also means a High Heat of Vaporization So…Many mammals use sweating or panting to remove excess heat  Water molecules with most kinetic energy are able to break H bonds and leave – these are the warmest water molecules, so it “cools” us.

Because Water is Polar: Consequence #2  Low temperatures (less kinetic energy) means molecules move energy) means molecules move more slowly…This allows Hydrogen bonds to form better so… Water molecules spread out Ice is LESS DENSE AND FLOATS! That ice layer insulates the water below- nice and cozy! Floating ice insulates bodies of water and keeps sea life (pond life) swimming!

Because Water is Polar, Consequence #3: Water is a POWERFUL SOLVENT Sugar is slightly polar (-OH group), so water clings to it. Sugar (and other important molecules) dissolves in water and can be carried through the body to be used as energy.

Because Water is Polar Consequence #4  Water “organizes” non-polar molecules  Hydrophilic “water loving”, POLAR: water, alcohol “water loving”, POLAR: water, alcohol  Hydrophobic “water fearing” NON POLAR: fat, oil, wax “water fearing” NON POLAR: fat, oil, wax Lots of non-polar covalent Lots of non-polar covalent C-H bonds. Carbon and hydrogen share nicely – don’t make extreme charged areas of positive or negative. or negative. Water has little to hang onto, so it excludes fats, waxes and oils and clings to itself.

Because Water is Polar Consequence #4  Where in the lab?... Added oil and alcohol Added oil and alcohol  So some consequences to life?...  Alcohol and vitamin C dissolve quickly into blood  Fat does NOT dissolve in water – good for long term energy storage to use when needed.

Polar Consequence #4  Cell Membranes made of phospholipids, half hydrophilic, half hydrophobic  Form with hydrophilic parts facing outside and hydrophobic parts hiding inside Water outside cell Water inside cell

So… Four Major Consequences of Water being Polar:  1. Clings to other molecules  2. High Specific Heat  3. Powerful Solvent  4. “Organizes” non-polar molecules  Go back to your lab, add examples and improve explanations.  Could you talk about any of these in an essay? (What, Why, Example)  3 X 5 Card:  Using one of the above 4 Major Consequences?

 On your 3 X 5 Card: Name & Period  WHAT? Write down one of the Major Consequences of water’s polarity (you pick). Write down one of the Major Consequences of water’s polarity (you pick).  WHY? Describe why water acts this way (words/pictures). Describe why water acts this way (words/pictures).  SO WHAT? What is the big deal? What are ways this consequence impacts life? What is the big deal? What are ways this consequence impacts life?  Draw 3 water molecules with hydrogen bonds

 Name and period on 3 x 5 card Finish this sentence: one thing you learned today about water?  What questions do you still have?  Draw 3 water molecules in hydrogen bond formation.

4 Types of Organic Molecules  Carbohydrates  Lipids  Proteins  Nucleic Acids