Mar. 18-22

This week, I further learned about charges. A positive charge is one with more positive ions than negative ions. A negative charge is the opposite. But, what is a neutral charge? A neutral charge is one with an equal number of positive and negative ions.

But, I then wondered: Is it possible to have an equal amount but to not be evenly distributed? Indeed, it is so. This state is called polarization.

This is what I was thinking when the class was given an in-class demonstration. The sweater and the balloon initially didn't attract each other because they had neutral charges. But, that changed when the balloon was rubbed against the wall, it became more positive while the wall became negative. Using my prior knowledge, I assumed that this happened because I thought that as electrons were being transferred from the balloon to the wall, the wall became more negative while the balloon became more positive.

But, how did the sweater attract to the balloon? How did it become negative? Doesn't this only apply to things with a positive charge while the other has a negative charge? It turns out that both went through charge induction, which I at first thought it was when opposite charges were brought together through neutral charges. But, what charge induction really is, is when one object is charged near a neutral charge and changes the distribution of positive and negative ions in order to create two polar ends.

Essentially, the balloon was moved to the wall and nothing happened initially since both were neutral to start with. Then, when it was moved to the sweater and back to the wall, it polarizes the wall shifting the   negative ions from the positive ions.

I then wondered why the negative ions were moved rather than the positive ions. Did it have to do with the greater electrostatic strength of positive ions than negative ions? Or was it because the opposite charges of positive ions and negative ions held each other in place? It seems as if though this is the case because I think that the positive ions are stronger than the negative ions. I theorize, although most likely erroneously, that the electrostatic strength has an inverse relationship with the number of electrons. It seems as if though the negative ions have less strength because they have a greater number of electrons than the positive ions. The reason I think this is so is because I think that the less electrons there are, the less pressure is being put on the "electro-chain" that holds the electrons in place. Hence, the charge of positive ions is stronger than that of negative ions.

I then wonder if this could play into the particle attraction between solids, liquids, and gases. It seems like the positive and negative ions lock the location of the particles based on their charges, hence bringing the molecules together. This may be influencing the decreasing ph and th energy in a liquid, hence slowing the  the particles and decreasing the amount of space they move and turning to solid as the particles form a strongly attracted lattice structure.

A liquid on the other hand, has less attraction between the particles than the solid, so they move about more freely. I think this may be because they have some attraction but mainly repel. I think they partially attract because if they didn't when a liquid is in a container, the particles in the liquid would still move farther apart. But, because there is less space to spread out, the particles don't move apart as much.

A gas, on the other hand, seems to repel even more than a liquid and a solid, with little or no degree of attraction. If a gas were not in a container, the particles would move freely due to lack of attraction, which would explain why pollutants in the air can spread out so much in the atmosphere, aside from the winds. But, if a gas were in a container, the particles would have some degree of attraction but less than a liquid. There is a greater probability that gas particles could move apart from each other and then collide again because there is less space for the particles to move around in the container.

Overall, substances can change state because of their changing electrostatic forces and attractions between particles at an atomic level.

This same principle also applies to ionic compounds, which form when ions transfer electrons to form neutral compounds. Through the exchange of electrons, one element, of course, becomes positive while the other one becomes negative. This is what happens when NaCl combine. The Na needed to lose an electron while the Cl needed to gain one. So, through this "electron exchange", the Na became positive and the Cl became negative. They then formed an ionic compound, which means a neutral compound has formed through electron exchanges with ions.

March 11-15

This week, I learned about atomic charges through a class demonstration. When a classmate rubbed the pen on his shirt, he then held it up to the match and the match moved–without any physical contact. This can be explained through charges. But, what is a charge? I thought that the charge was associated with the rubbing of the pen on the shirt since it was the only way to explain why the paper clip moved. Indeed, this was so.

J.J. Thompson's Plum Pudding model

The first thing I learned was that a charge involves static electricity. I then realized this supported my hypothesis because the pen did receive a charge through the electrostatic exchange with the shirt. Secondly, the charge is based on the flow of electrons. Electrons are the smallest possible component of an atom. Hence, this changed the way we thought about particles–that contact with other particles could only move another thing. But, one thing that does remain the same, I observed, is the exchange of energy. The exchange of energy would have allowed the pen to have moved the paper clip without touching it, just like energy is needed to change the th or ph phase of particles.

Based on this, I realized that we would have to change the way we draw particle diagrams to represent them at the smallest level. Particle diagrams in the past units could still be drawn the same using dots to represent particles. But, to draw the new particle diagrams, I thought of two possible ways to draw them: 1) Draw a circle to represent a particle and inside the circle, use + to represent positive and – to represent negative. 2) Draw a circle and inside the circle, draw dots to represent the charge. The second option is how we draw them.

Charges occur when the electrons transfer from one place to another. Depending on the charges, they could charge with other things. This is what I learned in the sticky tape lab. In this lab, we tested two pieces of tape: one tape taped onto another tape. The objective was to test the top tape and the bottom tape with other things to determine whether they would repel or attract. The top tape that was ripped off the bottom tape seemed to attract to the bottom tape. But, why? I at first thought that the top tape got charge after tearing it off of the bottom tape while the bottom tape lost the charge in the process. Through this, I also concluded that if they were both pieces of tape, they would have the same number/kind of particles, so there charges would remain the same if they didn't already create a charge. Hence, I think it is possible that the kind of particles a substance has can determine its charge.
Next, the bottom tape was tested with the paper and the aluminum. The bottom tape attracted to the aluminum, but repelled the glass rod. Hence, the aluminum must be positive while the glass rod was negative. Through this example, I learned that opposite charges attract while the same charges repelled–much like magnets. This is so because if the bottom tape and the top tape attracted together, they have opposite charges because when the top tape was ripped from the bottom tape, the top tape became positive while the bottom tape became negative. So, if the top tape is positive, then it would attract to something negative, like the glass rod, for example.

I then thought to myself whether charges and the flow of electrons have to do with electricity. I thought that this was the case because in the electrolysis lab, I learned that the cathobe and the anobe connected to the metal ends at the bottom of the trough, hence allowing electricity to flow through in order for the H2 and the O2 to separate from water. As I thought about this, I thought that metal was a conductor of electricity, and I also realized that oxygen and hydrogen had different charges. Otherwise, hydrogen and oxygen wouldn't have been separated from water. I then remember that the trough was made of glass, and knowing that it has a negative charge, I concluded that it couldn't allow electricity to flow through, whereas, metal could conduct electricity through the exchange of electrons.

This was the generalization I came to. To prove this, my group and I tested the conductivity (the ability to transfer electrons) of certain materials, such as: brass, silver, iron, zinc, copper, plastic, cardboard, and glass. The equipment we used included two battery sets, wire clips, and a light bulb. With the generalization I came up with, I predicted that the metal products would be conductive while the nonmetals would not be conductive. This prediction was correct because when all the metal products were connected to the wires, the batteries, and the light bulb, the light bulb lit, hence the electrons flowed through the wires to the light bulb. The nonmetal products, however, did not conduct electricity because the light bulb did not light up.

March 4-8

This week, I learned more about the complexities of finding the number of moles. The simple part I learned was the part where I could find the number of moles for 5g of a substances with the given: for every mole of this substances, it contains 10g. So, then I would proportionally equate them and find that for every 1/2 mole, there are 5g of this substance.

However, I still wondered how did scientists find the empirical formula of water to be H2O? This I was curious to find out. I wanted to learn the process of how to get there since I already know the answer. But how do I get there?

Due to the ACT/MME days this week interfering with class time, I could only write about how to find 1) how to find the empirical formula of a compound 2) how to add moles together to find the number of moles in a compound.

But, the complex part of molar mass was to find the empirical formula of a compound with the given: the percentages of the elements chemically combined in the compound. The first step to doing so is to divide the mass of the substance in 1 mole of the compound by the mass of 1 mole of the compound–this is to find the percentage of the element in the compound.

For example, let's find the percentage of H2 in H2O. Volume-wise, we know that H2 is 2/3 of the volume of water, but is it the same thing for the mass? Before I learned about atomic mass and molar mass, I figured that it would be different because mass and volume are two different things, and I had a feeling that hydrogen would have less mass than oxygen. When I found out how much H2 was in water, this supported my hypothesis. The formula to find the percentage of an element in a compound is:

mass of the element in 1 mole of the compound
------------------------------------------------------------   *  100
mass of 1 mole of the compound

I divided the molar mass of diatomic hydrogen (2g) by the total molar mass: 2(1) + 16=18g/mol. I found out that the percentage of H2 in water in terms of mass is 11%. Oxygen would then obviously consist 89% of water's mass.

Then, I wondered how I could use this to write the empirical formula of a compound. I then thought to myself that the best way to do so is to find the percentages of the elements first, one by one. To do so, I would divide the percentages of the elements by their molar masses to find the percentage of the mass of moles.

Then, I would take those answers and divide them by the smallest answer. These answers are the ratios of the elements in the compound, which will be used to determine their empirical formula. With a ratio of 1 to approximately 30.65 (to be exact 1,134/37). If I said the empirical formula for this compound would be O^1H^30.65, this wouldn't make sense. Instead, it should be O^37H^1134. This makes sense because one of the most important rules in writing an empirical formula is the subscripts must be whole numbers, not decimals or fractions.

While learning about this, I realized that if H2O were written as H^1.2O^0.6 or H^3.2O^1.6, the ratio always remains the same. This then reminds me that even if water's empirical formula were written either way (whether the correct or incorrect way), it would still be water. I then thought to myself that, that would be true for chemical currents. Through the electrolysis lab, I realized that the electrical current, which passed through NaCl water solution, split 1 particle of water to many. This would explain why hydrogen and oxygen would be separated into two different tubes based on the anobe and the cathobe plug-ins.

Now I have an idea of what would have happened if we did the electrolysis lab differently (e.g. turning the handle counter-clockwise instead of clockwise and plugging the anobe and cathobe differentlu). If that were the case, the result would be the same, but the process would be different. The electrical current would have gone in a different direction and splitting the particles through this, causing the hydrogen and oxygen to go into the other test tube. I am not sure this is correct, but this a rough idea of what I think happened at the particle level. But, one thing I know for sure is that the actual particles themselves don't change. There would still be H2 and O particles. Hence, through this lab, nothing entered or left the system to change the outcome of the results.

This week, I also learned about adding moles together.

To add moles together, consider whether they are diatomic or not. This is important. Here's an example of one:
2 mol H2 + 1 mol O2 (arrow) 2 mol H2O

But, why would it be 2 mol, not three as we learned in kindergarten that 2+1=3? Well, this isn't the case. Consider that in 2 mol. H, there are 4 H particles, and 1 mol. O2 has 2 O particles. Since we know that hydrogen is diatomic, it can combine with a single oxygen as well as a diatomic one. TIP: One diatomic element as well as a single element can be one mole. This is the case here. To make this problem easier, think of the number of particles involved and how they should be combined. With H+H+O and H+H+O, you get 2 mol of 2H2O (1 mol water=1 H2O). The overall trend I have noticed when combining moles is that the first compound being combined with another one determines the number of moles. (e.g. 4 mol Na and 2 Cl2=4 NaCl, hence 4 moles of NaCl) Na+Cl, Na+Cl, Na+Cl, and Na+Cl=4 pairs. Another trend I have noticed is that if there is a diatomic element, then there are twice as many particles as the same single element (e.g. H2 vs. H). Depending on the ratio of the elements, I've also noticed that determines the number of the moles of the elements combined together. (e.g. H2O: H to O is a 2-1 ratio, so 2 mol H2 + 1 mol O2=2 mol H2O).

Feb. 18-22

I learned this week in chemistry that if one knows the molar mass of an element, one can find the density of an element, such as hydrogen and oxygen. In the beginning of the electrolysis lab, I hypothesized that the density of hydrogen would be less than that of oxygen based on: 1) Hydrogen has the least atomic mass of all the elements on the periodic table. 2) In an electrolysis video I saw, I noticed that the bubbles in oxygen were packed more closely together while hydrogen's had more space in between.

Hydrogen, although less dense, has twice as much
volume as hydrogen as shown in the balloons.

For review sake, in water, hydrogen has a 2-1 ratio to oxygen. But, how does could one find this out? One clue is looking at the chemical formula of water (H2O). Obviously, this means that for every particle of water, hydrogen would have twice as much volume as oxygen. Why? Because it takes up twice as much space as oxygen.

But, how could I find a way to prove this true? Well, this week, my group and I did an electrolysis experiment. We had to hook up two probes to two metals ends at the bottom of the trough. We had to fill the trough with sodium chloride water solution. But, why not water? This is the part I felt I wasn't so sure of, but I think it had to do with the fact that sodium chloride could conduct electricity in order for the hydrogen and oxygen particles to chemically split.

Then, what we had to do next was use two graduation cylinders (one for hydrogen and the other for oxygen) and put them on top of the metal ends making sure that they are still full. The tricky part was to do so and sort of break the rules of physics–in other words, have none of the tubes with the sodium chloride water solution gravitate down the tubes. To do, I learned this with trial and error. It then came to me after the experiment that it was like the gas-trough lab where the bottles had to be filled with water and put in the trough and still remain full. The only difference, which screwed me up, was imagining that I was using a lens to cover the top of the tube. So, I had to approach this differently. Scoop the tubes with the solution and slowly tilt them to the bottom of the trough, then tilt it again toward the metal end and cover it with the tube without going over the top of the tube.

Scientific notation review:
a) With small numbers less than 1, the exponent is negative.
b) With large numbers greater than 10, the exponent is positive.

Then, after that ordeal was over with, I then cranked this device and repeatedly turned the handle clockwise. (Note: this device was hooked up with the electrolysis apparatus before we began the experiment). We then kept track of the volumes for each of the tubes filled with the hydrogen and oxygen. Every time we recorded the data, there was twice as much volume of the hydrogen as there was oxygen. One example of this being true is when hydrogen took up 8mL while oxygen took up 4mL. Now, the objective was to find the density of the gases. My group and I looked up the gases and found hydrogen to be 0.089 L and oxygen to be 1.429 L. But, since the graduated cylinders were measured in mL, we wanted the densities also in mL, so we converted by using proportions we learned from last week.

There was 3.5 mL of oxygen left in the tube. The question was to determine the molar mass of H2O by finding the molar masses of H2 and O through experimentation and mathematics:

To find x grams of oxygen for 3.5 mL:

3.5 mL*1.429g  *    1 L
              ----------   -------------
                 1 L         1000 mL

The answer is 0.005g, but by using scientific notation, the answer is 5.0*10^-3 g for oxgyen.

Twice as much volume as the oxygen, the volume of hydrogen left in the tube was 7 mL. Also, the same process was used for hydrogen in order to find the x grams of hydrogen per mL:

7 mL*   0.089g    *    1 L

             -----------     ------------

                 1 L          1000 mL

The answer is 0.000623g, but by using scientific notation once again, the answer is 6.23*10^-4 g for one hydrogen.

Based on this lab, I have concluded that hydrogen is less dense than oxygen. Therefore, my hypothesis was correct. Doing more research on hydrogen and oxygen to further support my hypothesis, oxygen has a greater atomic mass (16) than that of hydrogen (1). The atomic mass ratio between 1 oxygen and 1 hydrogen, therefore, is 16-1. But, the ratio with 1 oxygen to 2 hydrogens, is 8-1. This proves that oxygen still has a greater density than hydrogen–just a double dip ratio from 16-1 to 8-1.

But, I still wonder what would have happened if the probes (the anobe and the cathobe) were hooked up differently? Would that have altered the results possibly skewing them, or left them the same? Keeping in mind that everyone turned the handle clockwise, what would have happened if we turned it counter-clockwise? Would this have affected which tubes the hydrogen and the oxygen would have gone into? It seems to me in the picture above that the anobe attracts oxygen and the cathobe attracts with hydrogen. If that is to be so, then I think it's possible that oxygen may have a negative charge while hydrogen may have a positive. I think that since there are two hydrogens and 1 oxygen with a 2-1 ratio when combined to make H2O, I think that oxygen has a -2 charge while the two hydrogens have a -1 charge each. This would further help to explain why the two can chemically combine to form a compound. Now that I think about it, the anobe (negative) and the cathobe (positive) if were flip-flopped may have the same impact on where the oxygen and the hydrogen go. Here's some thinking ahead: Through the electrolysis lab, I wonder if next week I will learn about how electrons may tie into electrolysis?