Week 6 Blog

Ariana Trossen
Dr. Finnan
SG Chem 2
10/25/15

     We finished last week with our Unit 5 test, so this week we began Unit 6, which is all about the internal structures of particles. We looked at J.J. Thomson and his experiments with cathode rays. Then, we did our own experiment with sticky tape to understand the interactions it had with other materials. After that we tested the conductivity of different elements and compounds. Then, we went deeper by studying what was happening to the sticky tape as it interacted with the other materials and how its charge was affected. We also observed the electrolysis of CuCl2. To end the week we started looking at the composition of compounds that are solids that don't conduct electricity and found patterns in their equations.

     J.J. Thomson did experiments with cathode rays in the late 1800s. Cathode rays are beams of electrodes emitted from the cathode of a high-vacuum tube. We looked at three different experiments that he performed. In the first one, Thomson directed a beam at an electrometer and tried to separate the evidence of charge from the path of the beam. He found that cathode rays deposited an electric charge, and he found that he could bend the rays with a magnet. From this first experiment, he ultimately discovered that the charge was negative and cannot be separated from the rays. In the second experiment, Thomson tried passing the cathode ray through an electric field. When the ray beam passed through the electric field it bent. From this he concluded that cathode rays are charges of negative electricity carried by particles of matter. In the third experiment, Thomson did some careful measurements on how much the path of the cathode ray was bent in a magnetic field and how much energy was carried. Thomson was able to describe the mass/change ratio of the cathode particles. Thomson also came up with an amazing result from this experiment, he found that the mass-change ratio of cathode rays is far smaller than that of a charged hydrogen. This means that cathode rats either carry an enormous charge or are extremely light relative to their charge. From these experiments Thomson presented three hypotheses, only two of which were accepted as true. From those two a model of the atom was made, know as the Plumb Pudding model. This model will help us to understand the internal structures of particles.

     In the sticky tape lab we took a piece of tape and folded it, making a bottom half and then doing the same to make a top half. Then, we stuck the pieces of tape together and pulled them apart quickly to give them a charge. After that, we observed how the different pieces of tape interacted with each other and with paper and aluminum foil. We found that the top and bottom pieces were attracted to each other and the top and bottom tape both attracted the foil and the paper, but the top tape repelled itself and the bottom tape repelled itself. From this we determined that the top tape was positively charged, the bottom tape was negatively charged, and the paper and foil were both neutral. Ultimately from this lab we learned that positive and negative things are attracted to each other, two positive things repel each other, to negative things repel each other, and both positive and negative things are attracted to neutral things.

     This week we used Dr. Finnan's homemade conductivity testers to test the conductivity of different elements and compounds. We found that all metals and compounds with metals in them conduct electricity. Then, we discussed as groups about what we thought the reason was for the different things that do conduct electricity. Our group concluded that metals conduct because they have free electrons that flow easily and ionic compounds (a metal and a non-metal bonded together) conduct because they have free ions that move easily.

     To end the week we started looking at different compounds and their particle drawings and formulas. We were supposed to then look at patterns between the different compounds, but that's where we ended and I couldn't and still don't really understand what kinds of patterns I'm looking for. We also watched the electrolysis of CuCl2 and wrote down our observations as bubbles formed on the positive side, it smelled like a pool, and the bottom of the copper rod on the negative side began turning pink. After a little longer it continued to smell like a pool, the pink spread, and there were bubbles on both sides. Overall, this unit is very interesting and so far I like what we're learning.

Week 5 Blog

Ariana Trossen
Dr. Finnan
SG Chem 2
10/17/15

     This week in chemistry we did a lot of practice to prepare us for our test which we had at the end of the week on Friday. Our test covered Unit 5 which is all about counting particles. Last week we mastered the basics and were introduced to some more complicated concepts of counting particles. This week we mastered the more complicated concepts and showed our understanding on our tests.
Some of the more complicated concepts include calculating how many moles, molecules, or atoms are in an element or compound, empirical formulas, and molecular formulas. At the beginning of the week I felt a little unsure about these concepts, but now I feel a lot more confident about them.

     To begin the week we took a look at the packet from last week that asked about the number of atoms, molecules, or moles in an element or compound. Each group was assigned a different problem from the packet to whiteboard. Our group was assigned problem #7, which asked us to find the number of atoms in Bottle 7. Bottle 7 contained some iron nails. In order to solve the problem, we have to start by finding the mass of the bottle with the nails inside, then we have to subtract the Tare Weight (T.W.) from that mass. The T.W. is the mass of the bottle when it is empty. By subtracting the T.W. from the mass of the bottle with the nails we find the mass of the iron nails by themselves. After that you have to find what 1 mole of iron is by looking at the periodic table. Then you divide the mass of the iron nails by that number. This will equal how many moles of iron the iron nails are. With this new number you multiply it by Avogadro's number, which is 6.022×10²³, and you will find the number of atoms in the iron nails contained in Bottle 7.

     After more practice with problems solving for the number of atoms, molecules, and moles in elements and compounds, we began to look at empirical and molecular formulas more. The difference between empirical and molecular formulas is empirical formulas are based on data and molecular formulas are what the compound's formula truly is. Molecular formulas are generally more complicated, and empirical formulas are more simple. To find the empirical formula of a compound you have to start by finding the number of moles of each element in the compound. Then, you find the ratio of the moles to find out how many atoms of each elements are in a molecule of that compound. This will tell you what the empirical formula is. To find the molecular formula you start the same way as you do to find the empirical formula, but then you go on by taking the given mass of the compound and dividing it by the sum of the atomic masses of the elements in the compound. This will give you a number which you will multiply by the number of atoms you found for each element in the empirical formula. By multiplying, you find the more complicated molecular formula of the compound.

     Before the test we were given a review guide to cover everything we went over in Unit 5. From the definition of a mole to finding the percentages of elements that make up a compound, we reviewed for the test. Then on Friday we took it. I was a little nervous coming in, but as we started and I began to answer the questions with confidence, I wasn't nervous anymore. I feel that I have a very good understanding of the concepts in Unit 5, Counting Particles.

Week 4 Blog

Ariana Trossen

SG Chem 2

Dr. Finnan

10/10/15

     This week in class we continued to discover how to count particles. First, we ratio of masses of chicken eggs and quail eggs. Then, we looked at Avogadro's number, 6.022×10²³, which is a mole. After that, we began to calculate the number of moles in something and how one mole compares to other large numbers of things, such as cells in the human body. To further our understanding of counting particles, we did an experiment of reactions with zinc chloride to determine the empirical formula. We learned about Tare Weight next and how it helps us determine the mass of contents in a bottle. For homework this weekend we got a worksheet to help us to continue to practicing calculating the moles, atoms, and molecules in different objects and compounds. Before looking at Avogadro's number, we looked at the masses of chicken and quail egg samples.

     A standard chicken egg has a mass of 37.44g and a standard quail egg has a mass of 2.34g. From this we were able to determine that the ratio of masses between chicken and quail eggs is 16:1. Then, we compared larger samples of chicken and quail eggs, such as 10 eggs, 438, 1 dozen, and 1 million, In each scenario we found that the ratio of their masses is always 16:1. Using this information, we compared the masses of elements instead and found the same thing; the ratio of masses of two different elements, no matter how many atoms are in each sample, as long as they're the same, will always have the same ratio. Knowing this information makes it possible for us to find the the number of atoms in two samples of elements and find the masses of samples of elements. This also helped us begin to understand what a mole is.

     A mole is 6.022×10²³ particles, this is also known as Avogadro' s number. A mole is so big that you can't even count that high. To really understand how large a mole is, we compared it to the number of cells in the body of every human on earth. We found that mole is still greater than that. It is important to compare and understand ratios between samples and elements because it helps us to determine the relationships between them. We experimented on zinc to find out how it reacted with chlorine and their relationship.

     This lab we did was called the Empirical Formula Lab. In this experiment we put zinc and hydrochloric acid together. From this we were supposed to find the empirical formula of zinc chloride, a product of the reaction between zinc and hydrochloric acid. Empirical means "based on experimental evidence." Based on our experimental evidence we found that the empirical formula for zinc chloride is ZnCl2. We determined this by calculating masses and determining the number of moles of zinc and chlorine. By finding the ratio of the moles of chlorine and zinc and it equaled approximately 2, so the ratio of moles of chlorine to zinc is 2:1. After looking at how zinc and chlorine compare in zinc chloride, we moved on to look at sample containers of different elements and compounds to calculate the number of atoms, molecules, and moles.

     In class we were given multiple different bottles that contained different elements and compounds. Our worksheet asked us questions about how many atoms, or how many molecules, or how many moles were in each bottle. However, in order to find these things we needed to subtract the mass of the bottle from the mass of the bottle plus the element or compound inside. The mass of the bottle itself is known as the Tare Weight (T.W.).  Once we found the individual element or compound mass we could continue to calculate the moles, atoms, or molecules. To do this you have to know that the atomic number of each elements is equivalent to one mole of that element. If you are given a sample of an element, you can determine the portion of a mole that the sample equals. Each group in our class was assigned a specific problem to white board out, we were assigned problem #7. In this problem we were asked to find the number of atoms in a bottle of iron nails. In order to do this, we found the mass of the bottle plus the iron nails. Then, we subtracted the T.W. from the total mass, which gave of the mass of the iron nails. After that, we divided the mass of the iron nails by the atomic mass of iron. We then took that number and multiplied it by Avogadro's number, 6.022×10²³, and this gave us the answer of how many atoms were in the sample of iron nails.

     To end the week we were given a worksheet for extra practice on calculating the moles, atoms, and molecules. I am glad we got this worksheet. I feel the more practice I get with these problems, the better I am at solving them. However, I still don't feel 100% sure about all of them yet. I still struggle sometimes with knowing what numbers to divide or multiply by what. Ultimately, I feel I am getting better.

Week 3 Blog

Ariana Trossen
Dr. Finnan
SG Chem 2
3/10/15

     This week we took our Unit 4 test and started Unit 5. On Monday and Tuesday we spent time reviewing and preparing for the test. We started class on Monday by white boarding out the answers to the last two problems from Unit 4 Worksheet 4. Our group was assigned problem 6. By comparing the ratio of masses in two compounds, we can determine the formula for the  second compound based on the first. In this case we knew that compound 1 was water, with the formula H2O, and had a mass ratio of 1/8 (hydrogen/oxygen). The mass ratio of compound 2 was 1/16, from this we found that its formula would be H2O2, hydrogen peroxide. This is because we know the number of hydrogen in each formula stays the same based on the formula for water having two hydrogens and the numerators in each mas ratio, which represents hydrogen in each compound, are the same. The number of oxygens in compound 2 is twice the amount in compound 1 because the denominator, which represents oxygen in each compound, in compound 2 is twice that in compound one. We were able to determine the formula for one compound based on the mass ratios for each and knowing what one of the compounds was.

     On Tuesday we worked on the Unit 4 Review packet. We went back to the beginning of this unit and worked our way to the end testing our knowledge, before the actual test. First, we studied the differences between elements, compounds, mixtures, and pure substances. Elements cannot be broken down by chemical or physical means. Mixtures are variable; their physical properties depend on the composition, and can be separated by physical means. Compounds can only be separated by chemical means, and consist of two or more elements in a fixed mass ratio. We then identified different compounds, mixtures, and elements as particle drawings. 

    We continued our review by sketching out how different gases react to form compounds. An important thing we learned was about diatomic atoms. Hydrogen, oxygen, fluorine, chlorine, bromine, iodine, and astatine are all diatomic. This means that they don't occur as single atoms, but two of the same element bonded together.

      We reviewed further with mass ratio comparisons of different compounds, similar to problem 6 on Unit 4 Worksheet 4. With the ratios we were able to sketch particle diagrams of the two different compounds, and then write out formulas for each.

     Different elements have different properties, such as melting and boiling points. We showed this by using time and temperature graphs lines showing the relationships between different elements and their boiling points. If you were to have a mixture of two different elements, you could heat the mixture to the temperature of the lowest boiling point of the two elements and separate them in this way.

     On Wednesday we took the Unit 4 test, which covered all of these concepts. Then we went  on to start Unit 5, Counting Particles.

     To begin to understand the concept of counting particles, we looked at relative mass of different kinds of hardware. We discovered that by weighing things you can count them, by knowing the mass of something you can determine how many of that something there is.

     To end the week we began to dive into comparing the relative masses of different elements in various oxides. By this we were able to see how Dalton's assumption of relative mass compares to the adjusted relative mass. Since we did not have enough time to finish this worksheet in class, I am still a little confused on how they compare. Altogether, this week I feel very good about my knowledge on Unit 4 after scoring a 33/34, and am excited to continue learning how to count particles in Unit 5.