Our new unit is chemical equilibrium. To explore this topic before being officially introduced to it, we used the simulation and a few POGILs. I think that this is a good way of being introduced to something new, as it helps you get familiar with the topics by introducing similar things and starting off very basic. To reflect on these pogils I thought they were very useful in helping me get a good head start on the topic of equilibrium. Basically equilibrium is based on a major concept:
A reaction can go both ways - the forward and the reverse reactions.


At equilibrium, the overall rates at which the forward and reverse reactions occur are equal. Once equilibrium is reached, the concentration of the reactants and the products doesn't change because the rates are equal:

The most important concept in equilibrium is the equilibrium constant. The equilibrium constant, K_eq, is the concentration or the partial pressure of the products, raised to their stoichiometric coefficients, divided by the concentration/partial pressure of the reactants, raised to their stoichiometric coefficients. If this number is less than one, there are more reactants than products at equilibrium. If this number is greater than one, there are more products at equilibrium.

The second important concept is Le Chatelier's Principle. This states that if a system at equilibrium is disturbed, the reaction will shift in order to go back to equilibrium. There are three such disturbances:
     1. Changing the concentration of a reactant/product: If we add more reactant, the reaction will shift to the right, in order to make more products, and vice versa. In this instance, K_eq does not change because the ratio of concentrations is preserved.
     2. Changing the volume of the vessel: If we decrease the volume, the pressure will increase, so the reaction will shift to the side with less moles in order to lower the pressure back to the original, and vice versa. Again, in this case, K_eq does not change.
      3. Changing the temperature: This is the only way to change the equilibrium constant. If reaction is endothermic, and we increase the temperature, more products will be made, and K_eq will increase, and vice versa.
      To reflect on this, I think this principle is essential to equilibrium as a whole and I definitely need to understand it more. I came after school a couple of times to work on the equilibrium worksheets and I think I have a very good understanding of how to do most of the calculations in this unit. Rice tables are very easy for me now and I think that is a big part of this unit.


Adding a catalyst to the reaction will not change anything except the rate of the reaction. It will, however, change increase BOTH the forward and reverse reaction, making the reaction achieve equilibirium faster.

It is important to remember that solids and liquids do not play a role in the calculation of the equilibrium constant. Their concentration or partial pressure is always constant, and since K_eq is a ratio, they end up cancel out.

The last concept we learned was the relationship between thermodynamics and equilibrium. This was confusing at first, but now I understand it better, although I don't know how to answer some of the questions on the Equilibrium III worksheet. There is a relationship between Gibbs Free Energy and the equilibrium constant:

ΔG0=−RTlnK

To reflect on this entire unit as a whole, it definitely has not been as hard as I imagined it would be. I thought there would be very difficult calculations and the concepts would be extremely hard. So far, I've gotten down the calculations fairly easily, and although the conceptual stuff is pretty difficult, I am definitely starting to get it more.

ΔG0

            This week in class we did a full review of everything that has to do with gases. and did some demonstrations with liquid nitrogen, which was probably the most exciting thing we've done in AP chemistry thus far. We did a lot of whiteboarding of problems involving ideal gases and real gases. 

            The bulk of the week was spent working on problems from the Gases I and Gases II worksheets. The Gases I worksheet had a lot to do with problems that involved the ideal gas equation. This is PV=nRT. We can manipulate this equation to solve for any one of the four variables that can affect gases. An ideal gas is not something we actually see in real action but is just a hypothetical gas whose pressure, volume, and temperature can be described by this equation.  We also discussed a little bit the effects of STP and what it is exactly. STP is the standard temperature and pressure conditions of gases at 0° C and 1 atm. The volume of STP conditions is 22.4 L. We also faced some problems where P, V, and T all changed for a constant number of moles. When this happens we can set up an equation where P₁V₁/T₁=P₂V₂/T₂. This equation is very helpful for finding a final variable if we know all the initial variable’s and two of the final variables or vice versa for finding an initial variable. In reflection, these worksheets were very confusing and hard to complete at first, but after several sessions of whiteboarding I began to understand a little more.

            We also looked at some further applications of the ideal gas law. This involved density and molar mass. Since D=M/V we can substitute in variables for volume if we need to do so. We also know that molar mass is equal to mass per one mole of substance. We can use this knowledge to rework our ideal gas equation to solve for molar mass and density of gases. To reflect on this, I thought the ideal gas law was fairly simple and didnt involve that much thinking.

            We also touched on effusion and diffusion. Effusion is the escape of molecules through a tiny hole into an evacuated space. Diffusion is the spread of one substance throughout a space or throughout a second substance. There is an equation that is the same for both effusion and diffusion. We can use this equation to help solve for the identity of a gas based on its molar mass. I thought effusion and diffusion were pretty simple because the equations for them were very simple and not hard to work. 

            The last matter that we discussed was the deviation of real gases from ideal gases. This can be recognized by Van der Waal’s equation that corrects the ideal gas equation due to the finite volume occupied by the actual gas molecules and for the attractive forces that are present between gas molecules. This basically raises the pressure and lowers the volume. In reflection this concept was pretty easy to understand and apply.

            To reflect, this week was very hard for me because the gases unit is a pretty hard one in general, I did a lot of review this weekend and understand the topics much more than I did before but still need more work before the test. I thought the whiteboarding during the week also definitely helped me understand what was going on with the worksheets. The liquid nitrogen demo was very exciting and educational and was my favorite part of the week for sure.

A 12 minute video regarding effusion and diffusion

  This trimester  in AP Chemistry thus far we have been covering the topic of Thermodynamics. This topic covers both enthalpy and entropy as well as a few other concepts. We spent lots of time in class doing worksheets and using our famous white boarding technique. This technique has been very beneficial for myself and many other classmates all year as it allows us to see our other peers' thoughts and ideas and use them to learn more. We also spent a little bit of time doing a quick mini-lab that involved precipitates and net ionic reactions.

            In our introduction to Thermdynamics we discussed the difference between heat and temperature. From our discussion we concluded that heat is a measurement of the total energy that is present in the system while temperature is the measurement of the heat content of the system. In our introductory discussion, we also figured out that heat is due to the breaking or making of bonds. Temperature is also related to the transfer of heat. Lastly we learned that when heat leaves the system and goes to the surroundings it is considered an exothermic process and when heat goes into the system from the surroundings it is considered an endothermic process. All in all, to reflect on this concept, I thought it was quite simple to comprehend, although this would not really be the case for topics to come. Learning and understanding the differences between heat and temperature was fairly simple for me.

            Next we moved onto calorimetry. Here we continued to work on distinguishing between endothermic and exothermic processes. We worked on some worksheets using the formulas that we learned for the change in heat. Change in heat is equal to the mass multiplied by the specific heat capacity and the change in temperature. Calorimetry is useful to us because from this method we can find the energy change in the system by finding the energy change in the surroundings, and this can be very important. We also talked about the enthalpy of fusion and the enthalpy of vaporization. Enthalpy of fusion has to do with the process of melting and the breaking of bonds. When vaporization occurs the rest of the bonds are broken. To reflect on calorimetry, this began to really test me, and I was having quite a bit of trouble with it. After spending more time learning about calorimetry and vaporization, I began to comprehend it a little more, although I still definitely need more work before the exam.

            In our last topic we discussed entropy. Entropy can be defined as the possible number of microstates that are available to the system. It is represented as delta S in the equation. Entropy is greater than zero when melting or vaporizing takes place. It also occurs when the number of moles increases. Entropy can be calculated as the sum of the products minus the sum of the reactants. The last thing that involved entropy was Gibbs free energy law. This was used to figure out whether or not a process is thermodynamically favored. We also dived a little bit into standard state conditions and things of that nature. To reflect on these topics, I also thought they were very difficult at first. I had some trouble understanding how to apply the formulas and equations and solving. I also need more work on the topics of entropy and Gibbs free energy law before the exam.

            These were all of the main ideas that we covered this week. Basically they all go hand in hand with each other as they all fall under the larger scope of thermodynamics. Most of this unit had to do with math and I found that to be much easier and more helpful to my understanding of the topics. Equations and numbers make some of the concepts easier to understand because you are using set equations and concrete things. With the equations visible to me and understanding each of the factors in the equation, I can fully understand and comprehend what is going on in the process of each reaction. I would say I definitely participated in class rather well as I spent much time struggling with worksheets and whiteboards and discussing thermodynamics with my table as well as participating in class discussions. I would rate my understanding of the material at this point of time at 6/10.

Gibbs free energy equation

       This was not too difficult a week in AP chem, in terms of how much we did. I do not understand many of the topics thoroughly though, and I am quite nervous for this upcoming test on tuesday. The quizports helped a little but I still need more work which is a problem because I do not have any time on Monday. I hope I am able to study during class and during other hours in school so that I do well on this test.
   
        On Monday, we went over the white boards we made as table groups, as a class. We made these white boards on IMFs and all molecular bonding and what is related to it or depends on it. Some of these white boards contained a LOT of good information. These white boards talked about almost all aspects of IMFs and what they are, where they're located, and how strong they are. The other whiteboards didn't contain much, maybe a drawing or two that nobody besides them could understand. My white board was moderate. I believe we covered most of the subjects of discussion, but not all the small details that may be more necessary than they seem. I believe my table understands the material fairly well. To reflect on this whiteboarding, it was not too difficult of material and I understand most of it. Whiteboarding definitely helps me get things down.

         On Tuesday, we had no school. On Wednesday and Thursday, we worked on the work sheet named "AP WORKSHEET 02f: Bonding and Properties" and the packet named "Ionic Bonding, Metallic Bonding, and Intermolecular Forces". I am still working on mastering the differences between all the different types of bonding. After doing the Hot Pots and Task Chains, I feel as though it really helped me with understanding and memorizing all the things I need to understand and know for the test, which is really helpful. To reflect on the worksheet and packet I thought they were quite difficult. It is hard for me to know which intermolecular forces are involved when and what roles they play in boiling and melting points along with other things.

        On Friday, we did a mini lab sort of activity. I was partners with Julien and Yishai, as always, and we kind of joined up with Sarika's group. We decided to work on Part 2 first. Part 2 was the longer of the two parts, and we decided to do this first in case we ran out of time, so we could quickly and easily do the other part if need be. In Part 2, we used unknown substances. We had to determine the identity of the six unknowns, and we had a table of six possibilities. We drew the Lewis structures, and began putting the unknowns on the slides and the table. We quickly figured out which one was water, and which was glycerin. The other ones all had very low surface tension, and that was a characteristic of Acetone, Nonane, and Ethanol. I was able to figure out which was Acetone by wafting. I know the smell of acetone, because it is in nail polish remover. I used my sense of smell for the ethanol as well. What was left was the nonane. We also checked to see which ones dissolved into water easily. In the second part of part 2, we swirled these substances around, and we checked to see how viscous each was. The observations matched the ones we had from the first part of part 2. To reflect on this lab, I like working with other people in the class and it was pretty fun overall.

        In Part 1 of the activity on Friday, we tested whether or not substances conducted electricity. My group's predictions were a little off for the "In Aqueous Soln" column. I, for one, thought that they'd all be conductors, since water was a conductor. I found out only Sodium Chloride is a conductor when dissolved in water, out of these seven substances. I also found out that my whole center column was incorrect, besides Sodium Chloride. This activity helped me to understand that ionic solids are not good at conducting electricity AT ALL.

                                                                          
                                                                        Lattice Energy

 This week in chem, we began mastering our knowledge of IMFs, or intermolecular forces. We went more in depth into Van der waals forces, such as Hydrogen bonds, dipole-dipole, induced dipole, and London Dispersion Forces, or LDFs. We also touched on dipole-ionic bonds, and the forces between metals, which are not Van der waals forces. We began the week working on a POGIL on Intermolecular forces, or foced between molecules, in liquids and gasses. This was a bit tough to do, but after the reading you gave to us, it became easier and easier the more we read at my table. That night I also watched some lectures on it, and the POGIL started to become completely clear to me. I was able to finish it with ease after reading the packet and taking notes on these forces. Since we did a lot of practice on these things, it is now sticking in my mind, and I won't forget it for the test. To reflect on this, it was helpful in allowing me to fully be able to understand and memorize everything about intermolecular forces, this is helpful because I will definitely need it for the test.

        Later, in our table groups, we started on a "water" POGIL. This POGIL was fun especially the magnet part. My table didn't have any trouble in this POGIL, besides a few disagreements here and there which were solved by explanation. This POGIL helped me and my table understand Hydrogen bonds, induced dipoles, and sizes of different atoms in a molecule like NaCl, or sodium chloride. I think we could possibly use more of an explanation on this, but we get the gist of it. To reflect on this pogil, I could definitely use more work on the topics covered. I hope we will do more things with hydrogen bonding, induced dipoles, and the sizes of different atoms in a molecule.

         Putting our answers on the board for the Lecture 23 Intermolecular force worksheet really helped my table. Most groups got the answers right, just not the explanations. We were one of those groups. The wrong explanations helped, because you were then able to explain exactly what everyone did not understand, and change our answers so we would remember what we did wrong. Some people got the explanations right, and they were able to explain how they got those answers. To reflect on this, whiteboarding definitely helped me understand the concepts we've learned a little better. My favorite part was when we were asked to summarize all the things we'd learned this unit on the whiteboard. this helped me remember things that we'd learned earlier and know the basics of them. Whiteboarding really helps me learn things by listening to my classmates' explanations.

         The homework this week was not a huge amount, which I really enjoyed. I was able to study more for this class as well as others. To reflect on this week in AP chemistry, we learned quite a few new concepts regarding the intermolecular forces. These concepts were not exactly 'hard' but they were difficult to grasp at first, but doing more work with the things we've learned has helped me understand them further.

    This week was another full and busy week of AP chem. We took a big test on Lewis structures and then worked for the rest of the week on ionic bonding. A little side note: our class took an actual AP Chemistry multiple choice exam and this was a very difficult test for all of my class.

            The first half of this week we spent on reviewing for testing and actual testing. We spent Monday on reviewing Lewis structures, polarity, hybridization, and VSEPR Theory. All of this led up to a huge test the following day. The test was a very comprehensive one and was a good challenge. I found the test to require quite a bit of knowledge on the materials that we learned but I felt pretty confident taking it. On Wednesday we took an AP Chemistry multiple choice exam which was pretty difficult. It was definitely quite difficult for me as a I only got 13 questions out of 60 right. To reflect on this, it made me very nervous for the ap exam. I hope at the end of the year I am able to easily do well on this multiple choice exam.

            The last two days of this week we spent on doing a couple intro lessons to ionic bonding and metals. The basis for an ionic bond is a bonding between a cation and an anion. We can see that the formula will always have to be a balance between the negative and positive charges of two atoms. Ionic compounds will always be made up of a metal and nonmetal. Unlike covalent bonds, there is no sharing of electrons in ionic bonds. However, there is a strong attraction between the two ions due to the Coulombic force. Usually in an ionic compound there will be a negative charge on the metal and a positive charge on the nonmetal. The charges are generally determined by the group that the element is found in with exceptions for the transition metals. To reflect on this topic I thought it was very simple, it was a little hard to follow along at times during this lesson but I understood basically everything.

            We also learned about some properties of ionic bonds. We discovered that melting point can also be a representation of how strong the bond between the two atoms is. The higher the melting point, the stronger the bonds will be between the two atoms of an ionic bond. On Friday we spent a little bit of time on metals too. We learned about some of their properties and what alloys are. Alloys can be defined as a solution that has the properties and characteristics of a metal. To reflect on our work with metals I thought it was quite easy, although the concepts are likely to get much more complicated throughout the course of this unit.

            That's basically what we did this week. To reflect I thought it was a difficult week because I was very busy with soccer every single day. This made it very hard to find time to review for the test, although I felt very confident about it. I was extremely surprised that I didn't do better on the test and I really wish the tests were passed back in class so I can see my mistakes. Other than that I thought it was a good week of AP chem, my understanding of the new material was about a 9, and I participated in class activities well every day.

Example of an alloy

This week we had a lot going on in class. We did many different activities to help us better our understanding of the VSEPR theory and how molecular and electron domain geometries work.

            For the first half of this week, we worked online building our models that we had already learned about from our balloon and gum drop lab. We created a molecular orbital to represent our molecule and we could use this orbital to find out a lot of information. We looked at the dipole moments that occurred in the molecule and the individual dipole bonds that were present. From this we could see the partial charges in atom and could even better understand the partial charges in the molecule by looking at the electrostatic potential map. Atoms in the molecule that were the most electronegative appeared red on the map and the atoms that were least electronegative appeared as a cool color, either blue or green. We could also see the bond angles that were present in the geometries even though we already knew this from the worksheets and lectures that we had done previously.

            We found out from this lab that the unpaired electrons on the central atom are electron clouds that push down on the bonds of the molecule and reduce their angles and this is why they sometimes deviate away from their standard value.

            We also talked a little bit about pi and sigma bonds this week. Pi bonds occur when there is an overlap of the p orbitals while sigma bonds occur when there is an overlap of the s orbitals or sp orbitals. This concept was a little complex at first to understand but made more sense to me when I understood that sigma bonds occur in all bonds while pi bonds occur in bond orders that are higher than one (i.e.: a double or triple bond). For a double bond there is one pi bond and one sigma bond while for a triple bond there are two pi bonds and one sigma bond.

          The last thing we talked about this week is hybridization. This has to do with the amount of bonds and unshared pairs of electrons around the central atom in a lewis structure. For example if there are 2 bonds the hybridization is sp, if there are 3 it is sp2, and so on. Eventually you need to start using the d orbital. To reflect on this topic I thought it was quite easy and simple to understand, all you have to do is be able to count.

          To reflect on the entire week I thought I had a very good understanding and I participated well. At first I didnt really understand much of what was going on with bonding. This weekend I really spent an extremely long time working on chemistry and doing the quizzes online and now I feel extremely comfortable with the material. I now feel like I am a 9 on a scale of understanding the material. I am very happy because I was extremely anxious last week that I would not do well on this test, but now I am very comfortable with the stuff we've learned.

Here is a twenty minute video further explaining VSEPR theory: http://www.youtube.com/watch?v=nxebQZUVvTg