A peek inside the everyday happenings of our classroom. This is an interactive learning environment for students and parents in my Honors Chemistry 173 class. This ongoing dialogue is as rich as YOU make it. Visit often and post your comments freely.
In class on Thursday December 20th and Friday December 21st we did the Properties of Nuclear Radiation Lab. In this lab we were trying to figure out which type of radiation (alpha, beta, or gamma) would travel the furthest and which ones are easiest to shield. We did so by placing beta and gamma saucers in a Nuclear Scaler.
* We did not have access to alpha saucers, but Mr. Lieberman provided the results.
Beta and Gamma Saucers
Nuclear Scaler
There were 6 shelves in the Nuclear Scalers and the saucers were tested twice on each shelf.
Then the tests were repeated on the 2nd shelve from the top with different shields in place.
The shields could have been anything. Some examples were: Thick Lead, Thick Plastic, Thin Lead, Thin Plastic, and Paper.
Make sure everyone makes 2 graphs one for the different shelves and one for the different shields each with a line for the 3 types of radiation.
This Lab will be due when we return from break. Also, Everyone should start to study for finals.
Hey guys! So today in class we completed the Metal Reactivity Lab which had some pretty cool reactions in it. We started off the class, however, with watching some videos about Metal reactions and how the place on the periodic table corresponds with how strong a metal reacts with water (H2O). Both videos showed some pretty cool explosions and in case you want to watch it again, the episode of Braniacs is below even though everyone knows the explosions were fake :/
After the videos, we proceeded on with the lab. We began by taking a well plate and filling three wells with H2O, three wells with phenolphthalein, and three wells with HCl. Next, we took three pieces of magnesium ribbon, three pieces of aluminum ribbon, and three pieces of calcium metal and put one piece of each in their own wells in each of the liquids. We observed the reactions that took place and recorded them in a data table that will go into our lab books. It is a pretty straight forward lab and hopefully you understand the main idea that as you move down a column on the periodic table, elements become reactive in contrast to when you move across a period and the metals become less reactive. The images below show what happened in the the experiment. There are no picture of the elements in phenolphthalein because no reactions occurred.
Magnesium in HCl
Calcium in HCl
Aluminum in HCl
Aluminum in H20
Calcium in H2O
Calcium in H2O
Magnesium in H2O
I hope you guys have a good weekend and I would just like to remind you that the Alternate Universe Periodic table is due Monday along with this lab. The test is Tuesday and the Webassigns are due that days as well!
Next scribe will be Chris!! Don't worry it's not that bad :P
Yesterday was a great Monday in Chemistry! We started off class with some demos about elements patterns and properties. Mr. Lieberman brought us over to the flame hood and burned small samples of lithium nitrate (LiNO3), sodium chloride (NaCl), potassium nitrate (KNO3), copper (Cu), and strontium (Sr). Along with admiring the pretty colors that the flames gave off, we also observed that elements in the same group or family tend to have similar properties. We discussed how this might be a real-life application in investigating a crime scene with chemical residue, testing elemental properties, or making fireworks.
Here are the videos:
Using the information from this demo, we then played electron configuration battleship. Everyone was given a sheet with two identical periodic tables on it, but these tables were the extended version with the bottom two rows of the lanthanides and actinides placed in their original spot. Instead of using numbers to locate each element, we used the endings of their electron configurations. We observed some key patterns during this.
Here's a clear picture of the general patterns we found:
Here's one of every element individually labelled with their ending electron configuration:
(PLEASE NOTE: Helium (He) in the top right is different in that it ends with 1s rather than 1p.)
Towards the end of class, Mr. Lieberman demonstrated how we can use these configurations to abbreviate the entire electron configuration. Since, as good chemists, we only care about the electron that will react, we can use the previous noble gas to speed up the process. For example, if I wanted the electron configuration for uranium (U), I would write [Rn]7s2-5f3 rather than starting all the way from 1s1. If you're confused, make sure to come in for some extra help!
We didn't stamp the homework today, but the rest of the electron configuration packet it due for tomorrow! Also, keep in mind that tomorrow we have a sports assembly during period 2, so if you are missing that for marching band or a sport, make sure to check Moodle for the work you missed!
The next scribe will be... Rachel S.
Sunday, December 9, 2012
Quantum Numbers
Thursday and Friday in class we learned about quantum numbers and electron configurations! The three coordinates that come from Schrödinger's wave equations are the principal (n),angular (l), and magnetic (m) quantum numbers. These quantum numbers describe the size, shape, and orientation in space of the orbitals on an atom. The principal quantum number (n) describes the size of the orbital. Orbitals for which n = 2 are larger than those for which n = 1, for example. Because they have opposite electrical charges, electrons are attracted to the nucleus of the atom. Energy must therefore be absorbed to excite an electron from an orbital in which the electron is close to the nucleus (n = 1) into an orbital in which it is further from the nucleus (n = 2). The principal quantum number therefore indirectly describes the energy of an orbital. The angular quantum number (l) describes the shape of the orbital. Orbitals have shapes that are best described as spherical (l = 0), polar (l = 1), or cloverleaf (l = 2). They can even take on more complex shapes as the value of the angular quantum number becomes larger. There is only one way in which a sphere (l = 0) can be oriented in space. Orbitals that have polar (l = 1) or cloverleaf (l = 2) shapes, however, can point in different directions. 3) We therefore need a third quantum number, known as the magnetic quantum number (m), to describe the orientation in space of a particular orbital. (It is called the magnetic quantum number because the effect of different orientations of orbitals was first observed in the presence of a magnetic field.)
I apologize for everyone who needed to read the blog yesterday because I wasn't feeling well and forget to write it.
In class on Wednesday, we learned about the development of the Atomic Theory.
First of all, everyone must know that in the olden times, philosophers and scientists could just claim their theories and people would have to believe them. As times when on, scientific data and evidence started being used. Dalton was the first philosopher to use data to support his atomic theory.
John Dalton(Late 1700)
-The atom were tiny, indivisible, and indestructible particles
-Each atom had its own individualistic properties to determine which element it was
-Each element was different because of their different masses
At Dalton's time period, it was amazing that a scientist had used proof and data to back up their theory. Although it was not exactly the correct idea, he had made a great discovery for his times. Then, a scientist named J.J Thomson came and discovered more about the atom. Between the time of Dalton and Thomson, electricity and magnetism had been discovered.
J.J. Thomson (1897)
Through the cathode ray experiment (a vacuum tube with all air expelled from it), he created the plum-pudding model of the atom.
-There were positive charges throughout the atom.
-Electrons were floating around in the cloud of positive charge
-Particles have to balance each other out.
Here's a video explaining the cathode ray experiment.
After Thomson came Ernest Rutherford who conducted the gold foil experiment to also improve the atomic theory. Rutherford was a student of Thomson and wanted to prove his mentor's model, but then ended up discovering his own model.
Ernest Rutherford (1871-1937)
-Discovered the nucleus
-The nucleus had small dense positive charge
This is a video of how Rutherford found this model.
Through this experiment he found the nucleus, but do not confuse this with the fact that he discovered the proton and neutrons, because he did not.
Around the end of class, we learned a little bit about Waves and forms of energy. The speed of light equals wavelengths times frequency. (λν = c,λ=wavelengths, ν=frequency, c=speed of light)
Visible colors to the naked human eye are only a small portion on the electromagnetic spectrum.
-The shorter the wavelength, the higher the frequency which is more dangerous to us humans. (towards the gamma ray end)
-The longer the wavelength, the lower the frequency. Generally, these pass right through humans and are not dangerous. (towards the radio end)
-On the frequency bar, the colorful rainbow in the middle is the place where frequencies can be seen by humans.
In class, Mr. Lieberman did an awesome demonstration with glow in the dark paper and a purple laser pointer. Unfortunately, it was too dark to tape and I don't think anyone would've appreciated flash. Plus, it might have cancelled the effect of the demo. In any case, here's a similar situation of what Mr. Lieberman did.
He did this with a red, green, and purple laser pointer. Purple worked best, though, because purple is on the end with shorter wavelengths.
Hope this all made sense to everyone. Sorry about being late on this post again.
The next scribe will be Courtney Smith. Good luck!!! ^.^
Today in class we worked on the Molar Volume of a Gas Lab. The goal of this lab is to measure the molar volume of Hydrogen gas at STP.
First, we measured out 10 mL of Hydrochloric Acid and poured it into the eudiometer.
Then, we filled up the rest of the eudiometer with water.
Next, we took a small strip of Magnesium and shaped it into a little ball and wrapped the Copper wire around it, which was placed in the stopper.
After, we put in the stopper and placed the eudiometer upside down in the stand, somewhat in a beaker half full of water.
The eudiometer's contents started to bubble, which is the evidence of the chemical reaction, and created the gas. The volume of the eudiometer minus the volume of the liquid left in the eudiometer equals the volume of the gas created by the chemical reaction.
In order to find the mass of the Magnesium strip, you have to use dimensional analysis to convert the length of the strip to grams using the conversion of 10 cm of Mg = 0.1407 grams.
The barometric pressure is 30.04 in Hg (inches Mercury), which you have to convert to millimeters.
Your water vapor pressure depends on whatever temperature you got.
Don't forget to use Dalton's Law of P(total) = P(H20) + P(H2), so that you can find the pressure of the Hydrogen gas to then find the molar volume. The total pressure is the barometric pressure, and the water pressure is your water vapor pressure.
Hey Everyone! Today the lesson we learned was on Gas Stoichiometry. In class we went over our
Ideal Gas Law WKSHT that was due today (answers posted on moodle). We then spent the rest of the period learning Gas stoich.
Stoich using PV = nRT
Mr Lieberman pulled out the mole cannon today and used it as our demo for today's lesson. Here's the video. (Don't know why you guys are so frightened?)
1. So in order to find the pressure of the gas in the tube you have to make and balance a chemical equation. So this is it for the mixture of the solid and gases in the tube.
CaC_2 (s) + 2H_2 O ------> C_2 H_2 (g) + Ca(OH)_2 (aq) (sorry, underscore means subscript)
2. Next, you find the moles of gas formed from the reaction. Just a reminder, CaC_2 is the limiting reactant while the C_2 H_2 is the excess reactant.
.37 g CaC_2 1 mole CaC_2 1 mole C_2 H_2
_____________ x ________________ x _________________ = .006 moles.
1 64g 1 mole CaC_2
3. Next, you have to find the pressure created by the gas. In order to do this, let's use PV=nRT!!
P=? use PV=nRT or P= nRT/V
V= .87L (use the volume of cylinder that Mr. Lieb gave us)
T= 25 degrees Celsius + 273 = 298K (Has to be in Kelvin) (25 degrees is room temperature)
Moles= .006 Moles (work from above)
R= .082 atm/moles K (constant for gas)
Now that we have everything we need, we set up the problem!!!
(.006) x (.0821) x (298K)
P= _____________________
.87L
So in conlcusion, the pressure of the gas in the tube would be 0.17!
You could also solve stoich by using the Molar volume formula with STP. A.K.A. Standard Temperature Pressure
At STP, 1 mole of any kind of gas = 22.4L (Molar Volume)
Sample Problem: Sodium azide is used in airbags to cause them to inflate on impact. What volume of nitrogen gas is formed from the decomposition of 1.00g of sodium oxide (NaN_3)? Assume STP conditions.
So first is the balanced chemical equation.
3 NaN_3 -------> 4N_2 + Na_3 N
So we know this much....
T=273K
P=1 atm.
Let's use the formula
1.00g NaN_3 1 mole NaN_3 4 moles N_2 22.4L
____________ x ______________ x ______________ x ____________ = 0.46
1 65g 3 moles NaN_3 1mole N_2
See, you didn't have to use PV=nRT when you know you can sue STP! Time saver!!!
So that's pretty much what we learned in class today!
HMWK: Study for Quiz Tomorrow (Good Luck on it!)
Gas Stoich #1 WKSHT
Ideal V.S. Combined WKSHT
The next scribe is Danielle Sindelar!!! (Sorry to other people who wanted to be scribe)
