Tuesday, September 13, 2011
Tues-Day 2 - Welcome Parents!
AP Chem - we discussed the basis of solubility rules as caused by Coulomb's Law, which states that the attractive force between oppositely charged particles (cations and anions OR electrons and protons) is proportional to the PRODUCT of their charges and INVERSELY proportional to the distance (squared) between the particles. Thus, ions that have a +2 or +3 charge (or -2, -3) and are relatively small will have the strongest ionic bonds to all surrounding oppositely charged ions in a lattice, ergo even the multiple ion to dipole attractions that form between multiple water molecules and each ion is INSUFFICIENT to break the ionic bonds in the lattice, hence the salt tends to be insoluble.
For low charge (+1 or -1), large size ions (i.e. the relative distance between large ions in a salt's lattice is larger than the distance between smaller ions), the ionic bonds are relatively weaker so the multiple ion-dipole attractions to the water molecules per ion are SUFFICIENT to outcompete/break the ionic bonds and cause the ions to go from the lattice into aqueous solution. On our edline site, see the video of sodium chloride dissolving.
For low charge (+1 or -1), large size ions (i.e. the relative distance between large ions in a salt's lattice is larger than the distance between smaller ions), the ionic bonds are relatively weaker so the multiple ion-dipole attractions to the water molecules per ion are SUFFICIENT to outcompete/break the ionic bonds and cause the ions to go from the lattice into aqueous solution. On our edline site, see the video of sodium chloride dissolving.
Bio - we reviewed the scientific "peer review" process, and discussed "random error", which is not an "error" or mistake AT ALL. Random error is the unavoidable variation (positive and negative) among all variables and conditions in even the most perfectly performed experiment. Using a LARGE sample size in your groups will cause the AVERAGE of the random variation/"error" to be close to zero, thus avoiding distorted results.
In 11th, we discussed how to properly graph data, identify the independent and dependent variables, develop proper scales (range of data divided by number of boxes on the graph, then round to the nearest 1, 2, 5, or 10), connect the points, and make an appropriate title.
# posted by C @ 9:37 PM 
