Water and the Fitness of the Environment Chapter 3 Drops on plastic Paper clip
Molecule That Supports All of Life • Cells are ~70–95% water • Water is the main reason the Earth is habitable • Water is versatile!
water molecules and hydrogen bonding • Water is a polar molecule: • opposite ends have opposite charges • Note hydrogen bonds
Four emergent properties of water • Cohesion • water molecules “stick” together transports water against gravity in all vascular plants Adhesion – water H-bonds to other substance Water molecules stick together
Adhesion Water-conducting cells Direction of water movement Cohesion 150 µm The video
Surface tension = Cohesion at water/air surface BASILISK Detergent breaks surface tension
2. Water resists temperature change • absorbs heat from warm air, releases to cool air • Water can absorb more heat than air!
Burbank 90° Santa Barbara 73° Los Angeles (Airport) 75° Santa Ana 84° Palm Springs 106° 70s (°F) 80s Pacific Ocean 90s 100s San Diego 72° Absorption of heat by ocean cools the coast. At night, ocean releases heat to warm coast. 40 miles
Water has a high specific heat = amount of heat needed to change T of 1 g of a substance by 1ºC Water is liquid over a broad range of temperatures
What happens when a copper pot is used to heat water? • High specific heat = need to add more energy to water to raise its temperature!
What IS heat? Heat is energy • Heat=average amount of kinetic energy due to molecular motion • Heat flows from more energetic area to less (coastline example) • Faster moving molecule = hotter
Temperature • measurement of intensity of heat Celsius degrees (°C) • Room T = • Body T = • Boiling =
Evaporation= transformation from liquid to gas • Evaporative cooling • Surface is cooled as water evaporates • Sweating and evaporative cooling The most energetic molecules are released as steam. The ones left are cooler because they have lost energy
3. Ice floats • Ice is less dense than liquid water • Water greatest density at 4°C • If ice sank, all water would eventually freeze solid, making life impossible • Floating ice insulates, keeps water underneath liquid
The “locked” hydrogen bonds in ice space the molecules further apart, resulting in fewer molecules per equal volume of water Hydrogen bond Liquid water Hydrogen bonds break and re-form Ice Hydrogen bonds are stable hydrogen bonds in ice are more ordered in ice Most ectotherms cannot tolerate freezing: north american wood frog
4. Water is a great medium for dissolving substances like nutrients/wastes • Solution=liquid that is a homogeneous mixture of substances • solvent=dissolving agent • If water, the solution is aqueous • solute=substance that is dissolved • Ex. salt
hydrophilicsubstance has affinity for water • hydrophobicdoes not
colloid =stable suspension of fine particles in a liquid • Cant see in microscope, nevers settle out!
pH and solutions • Changes in concentrations of H+ and OH– can drastically affect cell • pH =measure of the [H+] of a solution • The pH scale is logarithmic pH = –log [H+]
Effects of Changes in pH • Acid = higher [H+] = lower pH • Acidic solutions pH < 7 • Base = higher [OH–] Alkaline/basic solutions pH > 7 • pH scale 0 – 14 • Most biological fluids pH ?
Acids and Bases HCl H+ + Cl - Acid or base? NaOH Na+ + OH - Acid or base?
Buffer Baking soda NaHCO3 - Na+ + HCO3- Bicarb ions can act either as an acid (donate H+) or as a base (accept H+ to form H2CO3). • Buffer =substance that resists changes in pH