Part 2 of the 3 Epic Post

Part 2. The Conductivity Lab (with the ghetto testers)

About a month and a half ago we did a lab called the "Conductivity Lab". Whoooooo! Very exciting right? Well kinda..... 

Background Information

The point of this lab was to further explore the ionization abilities of certain substances. The theory behind the lab was that different ions will gain or lose an electron to become stable. Take sodium for example (btw thank you Katrina for the idea...from your blog) has an electron configuration of 1s22s22p6s1. What this means is Sodium has one valiance electron. What this means is that often sodium (a metal) looses that electron to another element (a non-metal) in a ionic bond. 

              [An ionic bond is a type of chemical bond that involves a metal and a nonmetal ion (or polyatomic ions such as ammonium) that bond through electrostatic attraction. Simply put, it is a bond formed by the attraction between two oppositely charged ions.

The metal donates one or more electrons, forming a positively charged ion (cation) with a stable electron configuration. These electrons then enter the non metal, causing it to form a negatively charged ion (anion) which also has a stable electron configuration. The electrostatic attraction between the oppositely charged ions causes them to come together and form a bond.]

 This happens because elements bond to become stable, when Sodium loses that electron it becomes stable with an electron configuration like neon.  This "electron sharing" makes it a pseudo-noble gas with the stable configuration of 1s22s22p6. 

The Lab. Finally.

For the lab we mixed (dissolved) eight different substances into distilled water. The solution that was produced by the mixing was then tested by two different instruments. First the "ghetto tester". It was basically a battery hooked to a LED connected with two bare wires for insertion into the solution, which would complete the circuit if it conducts electricity (thanks to the amazing ions). If the solution is ionic (conducts electricity and completes the circuit) then the LED will light up. Sadly it won't give you a precise reading of the conductivity... 

Ghetto.....

Which is why we have a second way of testing. This other type of conductivity tester we used was the USB connected "conductivity probe". This probe used essentially the same type of circuit as the other tester (using the solution to complete the electrical circuit) with the only difference being that the LED was replaced by a voltameter. The computer uses the data from the voltameter to, using a complex equation, compute the conductivity of the substance.   

Probe

Below is the data table of results collected from the experiment, followed by a comparative graph of the different solutions conductivity.

            

Conductivity Results

The Graph^

So I made a graph about the data. It is quite beautiful. (Ok the font choices could've been better but...oh well) What the graph demonstrates is the relationship between different element's and their electroconductivity. The Y axis of the graph shows the electroconductivity of the element, measured in Microsemens per square centimeter (Yes I realize the intervals are screwy, the program I made it on is stupid) . The X axis shows the elements names. What we can learn from this graph is, Citric Acid has the highest electroconductivity (249.3 mS/cm2), and sugar water has the lowest with 16.1 mS/cm2. Sugar has a lower conductivity because sugar (glucose) is held together with a covalent bond (which is "crap for ions"), whereas Citric Acid is held together with an ionic bond which makes for amazing ions. Ions are key to conductivity because the shared electrons are able to move around. When you add electricity (a bunch of electrons) the electrons are able to jump from the negative terminal to an atom, and then from atom to atom, eventually returning to the positive terminal (of the power source) creating an electrical current.

Conclusion

In conclusion, an elements electron configurations determines if  If an element has electrons to lose/give away (to become stable), then that element will conduct electricity, because electricity is conducted by electrons (names make sense now don't they?) passing from atom to atom, resulting in an electric current. 

My Epic 3 Part Post (Don't Forget COMMUNITY STANDARD!!!)

So these last few weeks I have been feeling quite lazy, the result of an epic 7 page post in Biology, show week, Math Day, Harry Potter 7, and 3 hours of Jazz Band rehearsal this morning. But, I figured I had better'd make a blog post on The Periodic table, The Conductivity Lab and an Article Review.  Yawn, so here we go.......    

PART 1.    The Periodic Table. It has periods. And patterns. 

So, a long long time (1869) ago, in a land far far away (Russia), there was a magical prince (Nicholas Mendeleev), who created an amazing table of the elements. He named this table "The Periodic Table', named for the repeating patterns (periods) of elements.

Nicholas Mendeleev

 Back then there were only about 33 known elements (compared to todays 118 elements). Mendeleev arranged the know elements in ascending atomic weight starting a new row or column every time characteristics started to repeat. Now this same format had bee used by the chemist Julius Lothar Meyer but, two key differences made Mendeleev's table successful. One, he left gaps in the table where it seemed like elements had not been discovered yet. Granted he was not the first scientist ever to do this but, he took it one step further by using the trends in the table to predict the properties of the missing elements, like gallium and geranium (think the Unununium and Ununoctium of back then).

The second thing that he did differently was he occasionally ignored the order that atomic weights would suggest and switch adjacent elements like Cobalt and Nickel to group them better based on chemical properties. Eventually it would become apparent that he had (unknowingly, as atomic structure theories were still in the works) arranged the elements in order based on Atomic Number. Even later on, with the development of Quantum Mechanical Theories, it becomes apparent that each row of the table relates to the filling of the quantum shells of atoms.    

Mendeleev's Known Table

Mendeleev's Predicted Table

Today the modern periodic table has become the face of chemistry, gracing the walls of classrooms in colleges and high schools all over the world. In the last 151 years there have been some new additions to the table. Namely going from 33 elements to 118, and the discovery and naming of  the groups, periods, and blocks of the table. To further understand the way the table works you must understand the way that these three types of classification organize the elements.

Modern Table

Groups:
Groups (or families) are are vertical columns in the periodic table and also the most important way of classifying the elements. In groups 1A-8A (Main Group Elements) the elements in the columns share certain properties (Number of valence electrons, atomic radius, etc...)  all the way down the group. Each group has a  trivial name ie: 1A is the Alkali Metals, 2A is the Alkaline Earth Metals, 3A the Boron Group, 4A is the Carbon group, 5A the Pnictogens, 6A the Chalcogens, 7A the Halogens, and 8A The noble gasses. In groups 3B-2B (the Transition Metals) groups are named by the uppermost element in the group. In the "A" groups the groups number is equal to the number of electrons in the valence electrons.

Periods:
Periods are the horizontal rows of elements. The only places in the table where periods are more important for classification than groups are the d-block (transition metals, groups 3B-2B) and the f-block (inner-transition elements, lanthanides and actinides). The main use for periods is determining the number of electron shells for each block. Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomic number increases, shells fill with electrons in approximately the order shown below. The filling of each shell corresponds to a row in the table.

1s (Groups 1A and 8A, Period One (hydrogen and helium))

2s (Groups 1A and 2A, Period 2 (Li,Be)) 2p (Groups 3A-8A, Period 2 (B,Ne)) 

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f

6s 6p 6d

7s 7p

8s

Blocks:

A block is a set of adjacent groups. The block names (s, p, d, f. and g) are derived from the quality of the spectroscopic lines of the associated atomic orbitals: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. Blocks are sometimes called families.The s-block is comprised of groups 1A-2A, the p-block is comprised of 3A-8A, the d-block is comprised of groups 3B-2B, the f-block is comprised of the lanthanides and actinides, the g-block is hypothetically comprised of the predicted 8th period.

Now there are some other ways of grouping elements (platinum group, noble metals, etc...), but no one really cares about those, mostly because they're are not really used in high school chemistry. So to end this first part of my 2nd quarter post I'll leave you with another image of the periodic table labeled with some of the things I've discussed. Phew.

I can see the LIGHT!!!! but its bouncing off my eyeballs....

Its a wave, its a particle, no.......its LIGHT!!!!!!!! (or a unicorn if you're Niki)

So if you hadn't guessed it already this post is going to be all about Light! Yay!!!! This week in Chem we did a Spectra lab.  I other words we looked at different light sources (Some of the sources being low pressure tubes filled with a gas like Nitrogen or Helium that had an electric current run through them) through spectrascopes (Cardboard tubes with a special little plastic film on one end, and a tiny slit on the other.....sounds fancier than it really is.)  When you look at the light through the spectrascope the little slit limits the amount that passes through the tube into the the plastic. The plastic splits the light in to the different wavelengths (ROYBGIV).

White light Spectra through Spectrascope

The different light sources emit different wavelengths. When you look at the light through the spectrascope it is possible to determine the element in the light source based on those wave lengths.
In the above picture is a florescent light bulb as viewed through a Spectrascope. Because it emits white light (all wavelengths combined) you can see bands of all the different spectrums present in the picture. Other light sources emit different frequency's of light.  The different frequencies of light are caused by the electrons in the element being at different energy levels.

Energy levels:
-Bohrs Model---------Rather than having electrons located at fixed points in side an atom they are located within different energy levels (called orbitals in Bohrs model)

Bohrs Model

Electrons are located on the blue rings (they are impossible to locate at specific any time) they orbit the nucleus. When you add energy (in the form of electricity) the electrons jump to another level and back to their original level, producing energy in the form of light waves. The black spots are due to the element not being able to make those specific electron jumps. Today rather than orbitals electrons in a particle model are thought to be in electron clouds.

Cloud Model

In the cloud model the 1s, 2s, 2p, and 3s orbitals are the different energy levels. In the cloud model Electrons exist in probability densities which take on certain shapes, not orbitals.



The only problem with Bohrs model is that the math only worked for Hydrogen. Because of this people began to think that electron were waves. In other words, each electron also has a wave, (Thanks a lot to Louis Victor de Broglie) which can be calculated by the equation below, where h is the Planck Constant, and p is the momentum:

Bohr's Caption

With this formula you can calculate the wavelength of anything, therefor everything has/is a wave. Now your every day objects like a car have such a small wave length (thanks to that equation) that it is not noticeable (more like an object, less like a wave). But when you get down to the amazingly small objects like an electron the wavelengths become bigger, and noticeable (thanks again to that equation).

The Wave Model

So.......In conclusion the wave model is pretty far out there in left field for me (mostly because it a pretty new concept) but, I'm hoping that if I Google stuff repetitively,  and ask questions that I should grasp it before the final...hopefully.

This Week In Chem....(Lame Title Right?)

So this week in Chemistry was a bit of a refresher course in the history of the atom. I know, you're jealous right? Actually I remember that at some point in Intro to Chem I had learned all of key points (Rutherford's Model, Cathode Ray Tubes, Plum Pudding Model, etc...) but promptly forgot it all after the chapter test. The most important points that we cover this week include, the progression of models of the atom (Democritus, Dalton's Atomic Theory, Thomson's Plum Pudding Model, Rutherford's Atomic Model, and Chadwick's revised Atomic Model with the neutron. We also learned how they discovered the sub-atomic particles (Cathode Ray+ Magnet (Electron), the Gold Foil experiments (Protons), Chadwick's discovery (Neutron). The last bit of learning that went on this week involved Atomic Number (# of protons or electrons in an element, what makes and element that element) and Atomic Mass (# of Protons+ # of Neutrons, usually both #'s are equal unless it is an isotope(Element with extra neutrons)). So this all basically sums up the week in Chem, minus the completely off topic discussions that came up during homework time on thursday. I should've probably been doing more homework and less talking but, hey it all worked out...

Separation Techniques Lab

So this last week in Chem we have been doing a Lab on separation techniques... And now that the lab is over we are supposed to write a blog post on what we learned. The first technique that we worked with was filtration. Filtration works by running the mixture through some kind of screen or filter to separate mixtures, like sand from water. Another experiment that was done was separating iron fillings from sand, this was accomplished by using a magnet to pick out all of the fillings.

The experiment that worked I on was Distillation. The way that the experiment worked was that we took a mixture with 5.25g of sugar dissolved in 100ml of water and put it into a distillation apparatus.  The way that the apparatus worked was the water was in a flask on top of a heating element with a rubber stopper and plastic tube in the top of it that connected to another flask sitting 9 inches away on the table. (look at the picture if you don't get it) The water evaporates from flask 1 and the vapor travels through the tube (which was cooled by wet paper towels), condenses and drips down into flask 2. Once the water has all evaporated you are left with a mass of gooey sugar in the bottom flask 1. Once the water is all gone then you should take the sugar off of the heat otherwise you will end up getting a permanent layer of burnt sugar        in the bottom of your flask....which is no fun to clean off. Trust Me.

a

Distillation Apparatus

The last lab that we did was a chromatography lab. Chromatography works by having a solvent (water) dissolve ink that is on some kind of a matrix (filter paper). The lighter particles in the the ink are carried farther through the matrix by the water. The heavier particles stay farther back near the original line drawn on the matrix. After the water has traveled through the paper and the ink has separated there is a pretty cool pattern left on the matrix.

Chromatography!