September 2, 2015LIFE102StackMore on Chemicals & WaterChemical Wrap-Up- Ionic Bond: electrical attraction between an anion and cation- Ionic Compounds: Compounds formed by ionic bonds are not moleculeso Ie. Salto Compounds occur in nature in the form of crystals- Hydrogen Bond: occurs due to a slightly positive hydrogen bonding to a slightly negative elemento Not as strong as ionic bonds- Van der Waals Interactions: attraction between two surfaces;one large to one smaller o Weaker than hydrogen bonds- Hydrogen bonds/ Van der Waals Interactions are important because they are what allows molecules to stick together- All chemical reactions are reversible- Chemical equilibrium: point reached in a reaction where there is just as much reactions going one way as the other wayWater & Life*attracted to similar molecules**attracted to other molecules***carries water up a plantReactionProductReactants+2(H2O)O22(H2)September 2, 2015LIFE102Stack- Water’s polarity is key to life- Only common substance found in the three physical stages on Earth naturally- Tends to be attracted to itself (cohesion*)o o- Water is important to moderate temperatureo Organisms exist in the temp range between ice and vapor- Water expands 10% when it freeze (decreasing density)o Why ice floatso Insulates water underneath to prevent all water from freezing Allows life beneath the ice - Water is a great solvent o Ie. Water (solvent) Sugar (solute)- Hydrogen shell: surrounds proteins in colloids (protein solution)o Sometimes so much surrounds a protein the solution semi-solidifies Ie. Jell-O, Cells- Hydrophilic: attracts water; polar/ionic substanceso Ie. Xylem*** in plants- Hydrophobic: repels water; not polar/ionic *attracted to similar molecules**attracted to other molecules***carries water up a plantcal=amount of heat required to raise a g one degreeHeat energy released to the environmentg= cm^3+100 cal/g-100 cal/gHeat energy taken from the environmentCondensation (-580 cal/g)Evaporation (-580 cal/g)Freezing (+80 cal/g)Melting (-80 cal/g)VaporLiquidIceSeptember 2, 2015LIFE102Stacko Ie. Oil in water*attracted to similar molecules**attracted to other molecules***carries water up a