SciHawks

Physics - took the multiple choice part of the Waves 2 exam. We then began a procedure to determine the index of refraction of water.
The written response part of the exam is tomorrow, Friday. You will be provided with a protractor and ruler for this test; be sure that you know how to draw a ray at a given angle of incidence and refraction with the ruler and protractor.

AP Chem - took the single period Buffer/Titration exam.

Physics - we reviewed for the Waves 2 exam, going over multiple choice packet questions. Many review problems and practice tests are on Blackboard for your perusal as study aids.

We the began the process of quantitatively determining whether "complete" (99% or more) precipitation is occuring, if a precipitate does indeed form.

Physics - we looked at refraction quantitatively, using Snell's Law to determine the angle of refraction in a different medium, given an angle of incidence and the indices of refraction of the two media that a wave travels through.
We then saw that, when the refraction angle is 90 degrees from the normal, there is total internal reflection i.e. the ray does not refract into the second less dense medium! The angle at which this phenomenon occurs is called the critical angle.
Tomorrow, we will see the optical illusions that result from refraction of light rays.

Physics - we reviewed the wave diffraction and saw that the narrower the opening in an obstacle, the greater the degree of diffraction of the waves through that opening.
We then defined and looked at many examples of REfraction, the change in angle of a wave when it travels from one medium to another medium of different density.
We can measure the amount of refraction of one substance to another by measuring and comparing their respective absolute indices of refraction (found on the Reference Tables).
In general, light rays (which show the direction of travel of the wave) refract/bend TOWARDS the normal in a DENSER medium; by contrast, the rays refract/bend AWAY from the normal in a rarer/less dense medium.
Tomorrow, we will calculate the degree of refraction using the empirically discovered Snell's Law.

initial pH (easy), halfway to the equivalence point (very easy, if you understand what is in solution), at the equivalence point (longest, and most challenging), a bit/splash past the equivalence point (easy, if you make one important and logical assumption), and the limiting pH (easy).

Physics- took part II of our unit exam on Waves 1.

There are several major points on each curve that tell you the type and concentrations of the acid and base used.

Physics - took part I of the Waves exam.
We introduced the second part of our unit on waves, which focuses mainly on the phenomena of diffraction and refraction of EMR/light waves.
We came up with a definition of diffraction based on what it looks like, a wave's spreading out/bending around a barrier.
We also observed that, the narrower an opening is relative to a given wavelength, the greater the degree of diffraction.

double replacement, single replacement, gas-forming, metal-ligand, active metal in water, metal oxide in water, non-metal oxide in water, redox using a strong oxidizer, and select organic reactions: substitution, addition, esterification, combustion.

Physics- generally reviewed the entire unit, and then we did problems from a new review packet of questions.
Finish those problems as you study for Monday and Tuesday's test, and check Blackboard for the answer key.
NOTE: the formula relating the wavelengths allowed for a standing wave between two points has been corrected. See 03/15 or 03/16 notes. The formula should be length between initial and final node equals half of one wavelength time "n", where n is any whole number.

AP Chem - we did a basic buffer problem starting with the mixing of two separate solutions of the conjugates.
We then did our first buffer problem in which we REACT the buffer with a strong acid or strong base solution. The VOLUME of the solution changes, so we account for that with a simple organizer, the SRFC table. Notes and some tutorials are posted on Blackboard.
This unit and the next are the two most complex in this course. Study and practice problems/re-do the notes EVERY DAY.

Physics - we reviewed the Doppler Effect, and the Law of Reflection, noting that the angle of incidence is the angle between the original/incident ray and the NORMAL (perpendicular line) drawn from the surface.

We then discussed the meaning of "in phase" and "out of phase" with respect to:
1. two points on a given wave
2. two separate waves.

Two waves that are in phase will have constructive interference throughout.

We then introduced the term "resonance", which occurs when a wave (of energy) produces and in-phase wave in an object that will vibrate at the SAME frequency of the incoming wave, thus producing the maximum constructive interference, i.e. resonance!

We finished up the problems in Waves 4, and then we did a lab in which we measured the speed of sound in air at room temperature.

AP Chem - we derived the Henderson-Hasselbalch equation and showed the STRICT condition under which we could simply enter the INITIAL concentrations of the conjugates (from the question data/info) and know that these concentrations would PRACTICALLY be the same as their EQUILIBRIUM concentrations, the concentrations that MUST be used in any K expression.
We then showed that, when used appropriately i.e. when you can "neglect x/ % ionization", the formula yield a very quick and easy answer for the pH of the buffer.
We then did a more complex problem in which two solutions are mixed to form a buffer, so an initial molarity calculation must first be done.

Physics - we clarified the requirement for a standing wave: there must be a node (equilibrium position of zero amplitude) at each end of the wave; thus, any MULTIPLE of a HALF wavelength equal to the distance between beginning and final nodes will produce a standing wave. So, our formula for an acceptable wavelength that will produce a standing wave is length (from beginning node to final node) divided by 2n, where n is any integer. So wavelength = length/2n
Click on the image below (by the two dots) to see animation of interfering waves. 












AP Chem - we took the unit exam on Acids and Bases.

Physics - we finished the graph in which we calculated/drew the resultant wave from the superposition/interference of two waves.
We then listened to and saw a demo of the Doppler effect that shows how the frequency of a wave produced by a MOVING object will reach the receiver/hearer/viewer of that wave with a DIFFERENT frequency, due to the movement of the object that produces the wave. As the object moves closer to the receiver, the heard frequency/pitch is higher, whereas when the object moves away from the receiver, the frequency experienced by the receiver is lower.

We did a few more questions (5-7) in Waves 4.
On Blackboard, I will post links to the animations from this unit, as well as some helpful site, and all of the packet answers covered so far. Use these to study for Thursday/Friday's test.

We then quantitatively determined the pH of a buffer solution; we will use a shortcut method under certain STRICT conditions, later this unit.
SOME things to be sure to go over for tomorrow's exam:
1. pH calculation of a strong MONOPROTIC acid of given/known concentration
2.pH calculation of a strong base (either MONOhydroxy OR DIhydroxy!!!-beware trap!!!-see notes) of given/known concentration
(For 3-6, an organizer/ICE Table is suggested and probably helpful; either way, all work must be shown, step by step).
3. given Ka (OR pKa) AND concentration, determine pH AND percent ionization of a weak acid
4. given (equilibrium) pH AND concentration of a weak acid, determine its Ka OR pKa
5. given Kb (OR pKb) AND concentration, determine pH AND percent ionization of a weak base
6. given (equilibrium) pH AND concentration of a weak base, determine its Kb OR pKb
7. EXPLAIN, in terms of (1) H-X bond strength and (2) H-X bond polarity, the relative strengths of a series of acids.
8. explain, in terms of water hydrolysis by an anion, cation, or both ions, how a given salts forms an acidic, basic, or neutral solution. For solutions in which BOTH ions cause hydrolysis, determine, based upon given pKa, Ka, pKb, or Kb of the ions OR their CONJUGATES, whether the solution will be SLIGHTLY acidic or SLIGHTLY basic.
9. For reactions involving Bronsted acid base conjugate pairs, predict AND explain (based on given Ka, Kb, pKa, or pKb values and their meanings) the favored direction as the reaction proceeds towards equilibrium.

Physics- reviewed the various ways that waves are reflected and transmitted depending on the boundary rigidity/density; we then focused on the Law of Superposition - the superimposing of two waves on each other as they pass by the same point at the same time, resulting in constructive or destructive interference.
We looked at various "interference patterns", a tell-tale sign of waves that constructively and destructively interfere.

AP Chem - finished the unit with a review of Lewis Acid and Base reactions, focusing on the specific bond breakage and formation, noting the electron pair donors (bases) and acceptors (acids).

We then began our new unit on acid-base buffer equilibria by looking at the how and why of forming buffer solutions four different ways.

Physics - we finished up our Properties of Waves lab, showing the effect of reflection and transmission of a wave from one medium to another. We then worked on the Waves 2 questions in the packet.

AP Chem - we did the final permutations of acidic and basic salt problems; there is an additional problem posted in the notes in which the pKb of a base from a basic salt is determined, given the pH of a certain concentration of the salt. Finished the acids/bases by completing the acidic salt question and doing a basic salt problem; it is important to not only know the mechanics of solving these problems, but also knowing how and why a given salt is acidic or basic by drawing the reaction that is going on with water in the solution container.

Physics - demonstated standing waves, and observed the inversely proportional relationship between wavelength and frequency of a wave of a given speed. We also noted the node (equilibrium) positions and antinodes (maxima and minima) of the standing wave.
We then saw the rigid boundary inversion of a reflected wave, and the loose/moving boundary reflection that maintains the same direction/height of the pulse's amplitude.

We then began pH calculations for acidic and basic salts.

Physics -we reviewed the types and characteristics of waves. We then looked at the creation and characteristics of 'standing" waves. We also showed how waves can meet and undergo constructive or destructive interference- we simply add the amplitudes of the interfering waves to see the resultant wave.

AP Chem - finished up the explanations of acidic, basic, and neutral salts. We then began the formal explanations of acid strength based on bond polarity and bond strength.

Physics - reviewed wave characteristics and did the Waves 1 packet questions.

AP Chem - continued with the various permutations of weak acid and weak base equilibria question types.
We then explained the basis of acidic, basic, and neutral salts by looking at the ions that comprise the salt. The ions are either conjugate acids or bases, and thus may react with water to produce acidic or basic solutions.

Physics - we reviewed the Magnetism unit test; we then finished our magnetic field lines lab.
We reviewed the various properties/characteristics of waves, and then did the common calculations involving them, relating wavelength to frequency to period to speed of the waves. We also related the speed of a wave to the distance that a given part of the wave travels in a given amount of time
(d = v t).

We then applied the same process to weak bases i.e. ammonia and their derivatives, which we will continue tomorrow.

Physics - got into our unit on waves, discussing the common characteristics of longitudinal (particles move parallel to wave direction) and transversal (particles move perpendicular to wave direction) waves.
We further defined, and showed the AMPLITUDE (power, energy, brightness, loudness) of a wave, the FREQUENCY (number of wavelengths passing a given point per second), the WAVELENGTH (a DISTANCE between two EQUIVALENT points on the wave, usually peak to peak is used for convenience), and PERIOD (the number of SECONDS for ONE wavelength to pass by a given point).

With this, we can quickly calculate the equilibrium pH of a given concentration of weak acid, WITHOUT the need for a calculator; even WITH a calculator, the button-pushing is easier with the less complex denominator.
We also showed that, with increasing dilution (reviewed the lab process of dilution also), the % ionization of a weak acid increases, THOUGH the pH increases up until you have an infinitely dilute solution that has a pH of 7.

Physics- took the unit exam on Magnetism; we then worked on the magnetic field lines lab questions.

We then began weak acid equilibria problems; we listed the possible variables, and determined the pH of a weak acid for a given initial concentration.

Physics - finished up our magnetism unit doing an assortment of multiple choice questions that covered the 4 left-hand rules.

AP Chem - took the first Equilibrium unit exam.

Physics - MAGNETISM UNIT EXAM is on Thursday; one day only, multiple choice questions only.

We reviewed the first 3 left-hand rules for drawing magnetic field lines (the third is actually for determining the force on a current carrying wire or on an electron);
we used a 4th rule for determining the magnetic field lines emerging from a solenoid: curl the left hand fingers in the direction of the current looping around the solenoid; your thumb then points to the north pole of the solenoid/magnet - then you draw the lines (ANTS) as usual.
We did a magnetic field lines mapping lab.

AP Chem - we discussed the relative strengths of conjugate acids and bases; we then used the meaning of their relative strengths to predict whether products or reactants are favored for a given Bronsted acid base neutralization reaction.
Equilibrium I unit exam tomorrow! Study notes, and practice problems!