ch 3

Card Set Information

ch 3
2011-05-25 23:05:27
water molecules

Show Answers:

  1. how many hydrogen molecules can bond with water?
    maximum 4
  2. what is cohesion?
    the hydrogen bonds that hold a substance together.

    contributes to the transport of water and dissolved nutrients against gravity in plants.
  3. explain adhesion
    • the attraction between different kinds of molecules
    • or
    • the clinging of one substance to another
  4. eg: the adhesion of water to cell walls by hydrogen bonds helps counter the downward pull of gravity
  5. What is surface tension?
    the measure of how difficult it is to break the surface of a liquid.
  6. how does water moderate air temperature?
    by absorbing heat from the air that is warmer and releasing the stored heat into the cooler air
  7. what is kinetic energy?
    the energy of movement

    the faster a molecule moves, the greater its kinetic energy

    Heat is a form of energy
  8. What is temperature?
    A measure of heat intensity that represents the average kinetic energy of the molecules. Regardless of volume
  9. what is a unit of heat called?
    a calorie (cal)
  10. what is a calorie?
    the amount of heat it takes to raise or lower the temperature of 1g of water by 1c
  11. what is specific heat?
    the amount of heat that must be absorbed or lost in order for 1g of a substance to change its temp by 1c
  12. what is waters specific heat?
    1 calorie/ gram/ celsius
  13. how do you break hydrogen bonds in water?
    heat needs to be absorbed
  14. what happens when hydrogen bonds form in water?
    heat is released
  15. what is the relevance of waters high specific heat to life on earth?
    • a large body of water can absorb and store huge amounts of heat from the sun in the day and summer. and only warm up a few degrees
    • at night and winter the cooling water cam warm the air
  16. what happens with evaporative cooling?
    the increase in the kinetic energy can mak the molecules break free of hydrogen bonds and enter the air in a gas state
  17. the quantity of heat a liquid must absorb for 1g to be converted from liquid to gas
    • heat of vaporization
    • and emergent property caused by the breaking of hydrogen bonds
  18. what is a solution
    a liquid that is a completely homogeneous mixture of 2 or more substances
  19. a solvent is.....
    the dissolving agent of a solution
  20. a substance that is dissolved into a solution
  21. what is the name of a solution where water is the solvent
    an Aqueous solution
  22. what is molecular mass?
    the sum of all the masses of all the atoms in a molecule
  23. molarity
    the number of moles of solute per litre of solution
  24. when a hydrogen atom participating in a hydrogen bond between 2 water molecules shifts from one molecule to the other what happens?
    • the dissociation of water molecules
    • the hydrogen atom leaves an electron behind and a
    • hydrogen ion is actually transferred.
    • (h+) a single proton with a +1 charge

    • the water molecule that lost a proton is a hydroxide ion charge of -1 (OH-)
    • the proton binds to the other molecule making it a hydronium ion (H30+)
  25. what is an acid?
    a substance that increases the hydrogen ion concentration of a solution

    when acids dissolve in water they donate additional H+ to the solution
  26. a substance that reduces the hydrogen ion concentration of a solution
  27. basic solution
    solution with higher concentration of OH- than H+
  28. neutral solution
    OH- and H+ are equal
  29. define pH
    • a measure of hydrogen ion concentration egual to
    • -log(H+)
    • ranging from 0 to 14

    pH declines as H+ increases
  30. substances that minimize the changes in the concentration of H+ and OH-
    in a solution
  31. how do buffers minimize changes in the pH in a solution?
    accepting hydrogen ions from the solution when there's too much and

    donating hydrogen ions to the solution when they have been depleted.
  32. how does a hydrogen bond form?
    when the slightly negative charge oxygen of one water molecule is attracted to the slightly positive charge of hydrogen of a nearby molecule

    basis for waters unusual properties