Water Essay Grading Rubric

Name ______Period ______AP Biology

The unique properties (characteristics) of water make life possible on Earth. Select three properties of water and for each property,

a) identify and define the property and explain it in terms of the physical/chemical nature of water. b) describe one example of how the property affects the functioning of living organisms.

Identification - 1 pt Definition – 1 pt Elaboration – 1 pt Example – 1 pt polarity unequal charge electronegativity, Hd+, Od-, unequal sharing distribution tetrahedron, various Hydrogen bonding weak, intermolecular, electrostatic attraction various transient, attraction between Hd+ and Od- Cohesion Attraction of water H-bonding explained Transpiration, surface molecules for each other tension Surface tension Resistance to being H-bonding explained Water walking, water stretched striders, water held by soil particles Adhesion Attraction of water H-bonding explained Capillary action, molecules for other transpiration molecules High specific heat Absorbs 1 cal/g/C (or K) Water temp changes Moderates temperature slowly effects High heat of vaporization Energy required for liquid 540 cal/g/C, breaking H- Sweating, surface cools, to change to gas bonds coolant, high boiling point, water cycle/rain, transpiration Versatile solvent Dissolves many Dissolves by ionization Any valid biological compounds example Unusual phase change Solid>liquid>gas Ice floats (less dense), Nutrient upwelling, change crystal lattice, most dense in thermal mixing, at 4C, farther apart, more insulation layer of ice on H-bonds ponds Dissociation/ ionization 2H2O<> H3O+ + OH- pH scale based on H2O, Specific cellular or H20 <> H+ + OH- H2O pH = 7 (neutral) organismal example, electron source in photosynthesis, hydrolysis reactions Incompressibility Resists changes in volume H-bond influence Hydrostatic skeleton, due to pressure amniotic fluid, blood pressure, turgor Viscosity Resistance to flow Fish swimming, aquatic propulsion Poor conductivity Ability to allow e- flow Requires conducting Electric fish, eel solutes