Cells are 70% - 95% water- it is the medium of most everything biological.

polarity of water

two hydrogen atoms help to an oxygen atom by polar covalent bonds. oxygen is more electronegative than hydrogen causing the electrons to be closer to the oxygen.
oxygen will be slightly negative and hydrogen with the slightly positive.

The hydrogen atoms are attracted to other oxygen and the oxygen is attracted to the other hydrogen causing water to stick to other molecules of water.

The 4 emergent properties of water:

1. Cohesion & adhesion

   1. Cohesion

      • water sticking to itself.

      • water molecules are constantly moving around (in liquid state) and because of hydrogen bonding they form/ reform/break apart continuously but overall they stick to each other.

      • BIOLOGICAL IMPLICATION! This is useful in plants: water will travel up to the plant because as water evaporates out of the leaves (transpiration) the water will be “sucked” out of the ground.

   2. Adhesion

      • water molecules sticking to another substance

      • water sticks to the vessels inside of a plant, assisting in the movement up the plant. (example paper towels)

2. Moderation of temperature

   1. Heat - the total amount of kinetic energy due to molecular motion in a body of matter. temperature is the scale in how heat is measured.

      • heat will always travel from warmer to cooler until they are balanced

      • Calorie is the amount of heat required to raise the temperature of 1g of water by 1ºC. (kilocalorie- 1kg of water by 1ºC)

   2. very high specific heat is the amount of heat that must be gained or lost for 1g to change 1ºC

      • requires a great input of energy to raise the temperature

      • requires a great amount of energy to be lost to drop temp

      • can be summed up by saying water is resistant to change in temperature

        • Reason- the heat energy has to disrupt all the H bonds before the molecules can start moving at a faster rate.

        • Importance- stabilization of body and ocean temp

   3. Evaporative cooling

      • Heat of evaporation quantity of heat a liquid must absorb for it to go from liquid to gas state. Must break H bonds.

        • Warmest molecules leave the liquid state first, cooling the temperature.

          • A human body sweating and the earth's climate

3. Insulation of bodies of water by floating ice

   • -Each water molecule will bond to 4 partners in ice form- forms a lattice. Ice is 10% LESS dense than water at 4^°C. Once we go above 4°C the molecules will begin to spread out again.

   • Water is most dense at 4^ºC

4. Solvent of Life

   • Solution two or more substances evenly mixed

     • Solvent whatever is dissolved in the solvent

       • In an aqueous solution, the solvent is ALWAYS water

   • Hydration shells molecules surrounded and attached to water

     • NaCl

       • Na is slightly positive so the O in water will stick to this

       • Cl is slightly negative so the H in water will stick to this

     • Some hydrophilic molecules/atoms can be considered a "colloid” = stable suspension of fine particles in water.

Hydrophobic mixture (oil and water; non polar)

• Solute [ ] (concentration) in aqueous solutions-

  • Mole = 6.02 x 10²³ (avagadro’s number) daltons in one gram

  • Molarity number of moles of solute per liter of solution

• The hydrogen in a aqueous solution shifts from one O to another O. this shift will leave behind one electron

  • H ion (H⁺) proton with +1 charge

  • Water that lost its proton is called a hydroxide ion (OH^-) and has a -1 charge

• An H⁺ proton can bond to another water molecule forming H₃O⁺ (hydronium ion)

  • H₂O = H⁺ + OH^-

  • In pure water, H⁺ and OH- are usually about equal neutral.

• -Acid- Donates H⁺ to a solution (more H⁺ than OH^-)

• Bases- reduces the total amount of H+ by accepting hydrogen ions. More OH^-(fewer H⁺ than OH^-)

• -pH scale- In an aqueous solution at 25°C it is the product of H+ x OH-which will equal 1 - 14

  • Neutral = [H+] = 10^-7

    • = [OH-] = 10^-7

  • pH = -log [H+]. if neutral then -log 10^-7 = -(-7) = 7

  • A solution with a pH of 8 would have a H⁺ concentration of

  • 10-8 M. There is a tenfold difference for every step up and down scale.

• Buffers Minimize the chance in the [ ] of H⁺ and OH^-

  • Accepts H ions from a solution when in excess and donates them when they are low (carbonic acid in our blood)

  • Usually a molecule that has an acid/base pair

  • Most organisms need pH of around 7 at all times.