Biology

Chapter 4

Compounds

Concepts/Ideas/Facts:

Water:

  1. Chemical reactions of all living things takes place in water .
  2. Cell shape and cell structure depend on water
  3. Hydrogen bonds cause water to cling to itself and other charged particles
  4. Water heats up and cools off slowly or waters has a high heat retaining capacity
  5. Water has a stabilizing effect on temperature
  6. water is an excellent solvent
  7. ice is less dense than water

Definitions:

  1. POLARITY – because of the pull of heavier charged protons in the nucleus of an atom, electrons are strongly attracted towards the nucleus of the heavier  bonded atom.  This causes one side of the compound to have a negative charge and one side to have bonds.
  2.  POLAR COMPOUNDS – covalent compounds that have slightly charged positive and negative “poles” or opposite ends. Water has such a polar covalent bond.
  3.  HYDROGEN BONDS – the attraction of the polarized regions of water to the other polarized regions of water molecules.  In water the hydrogen is positively charged (H+) and the Hydroxide is negatively charged (OH- ).
  4.  COHESION – attraction force between particles of the same kind
  5. ADHESION – attraction force between unlike substances
  6. CAPILLARITY – the property of water to move upward through narrow tubes or spaces against the force of gravity.
  7.  HYDROPHILIC SUBSTANCES - water-loving substances due to polarity
  8.  HYDROPHOBIC SUBSTANCES - water-dreading substances due to polarity
  9.  TEMPERATURE - measure of molecular movement
  10.  SOLUTION - a mixture in which one or more substances are uniformly distributed in another substance. Solutions can be mixtures of liquids, gases, or solids. In a solution neither the solute nor the solvent are altered chemically.
  11. SOLUTE - the substance dissolved in the solution.  The particles of a solute may be atoms, ions, or molecules.
  12. SOLVENT - is the substance in which the solute is dissolved
  13. CONCENTRATION - the measurement of the amount of solute dissolved in a fixed amount of solution.
  14. "SPHERE of HYDRATION"  - the clustering of water molecules around a solute
  15. EVAPORATION - the converting of liquid water to a gas
  16. COHESION - the capacity of something to resist rupturing when stretched, or placed under tension.
  17. HYDROGEN IONS - positively charged hydrogen   (H+)
  18. HYDROXIDE IONS - negatively charged hydroxide  (OH-)
  19. HYDRONIUM ION - H3O+
  20. CARBONIC ACID - H2CO3
  21. BICARBONATE - HCO3-
  22. pH - measurement of the concentration of hydroxide ions (OH-) and hydroxide ions  (H+) in a solution.
  23. pH Scale  - a scale from 0 to 14 where 7 is neutral and everything above 7 is considered a base or alkaline (-) and everything below 7 is considered an acid (+)
  24. ACID - substances that donate protons (H+) when dissolved in water
  25. BASE - substances with a negative charged ion (OH-) that accept protons when dissolved in water.
  26. BUFFER SYSTEM - a dynamic partnership between a weak acid and a weak base that forms when the acid dissolves in water.  Buffer systems mediate ion concentrations in our bodies, blood, and cells.
  27. SALTS - compounds that dissolve easily and release ions other than H+ and OH-  in a solution.
  28. ORGANIC COMPOUND – generally derived from living things and contain Carbon
  29. INORGANIC COMPOUNDS – generally derived from non-living things a

Explanation: pH

The acidity or basicity (alkalinity) of a solution is related to the relative concentrations of H3O+ and OH-.  If the concentration of H3O+ is more than the concentration of OH- the solution is acidic. If the concentration of OH- is more than the concentration of H3O+ then the solution is basic. If the concentrations of H3O+ and OH- are equal to one another, the solution is neutral.

There is also an internal relationship between the concentrations of H3O+ and OH-. They are not independent of one another. As one goes up, the other goes down. They cannot both go up because the higher concentrations of H3O+ and OH- would react with one another to make water molecules. That is a consequence of the reversibility of the self-ionization reaction of water.

(2H2O <==>  H3O+ + OH-)

Explanation: Dissociation of Water

The breaking apart of the water molecule into two ions of opposite charge can be shown by the chemical equation below.  One water molecule dissociates to form two ions.  H+ and  OH-

H2O <==> H+  +  OH-    

The free H+ ion can now react with another H2O molecule forming hydronium..  H+ + H2O <==> H3O+  

 

Check this website out showing a concept map of hydrogen bonds, adhesion, cohesion, and so on

http://www.biologylessons.sdsu.edu/classes/lab1/semnet/cohesion.htm