Archives for September 2006

Introduction

Salts are substances that have the property of readily allowing water molecules to attach themselves to its crystalline structure. The water molecules that combine with the salt can result from exposure to humid conditions. When a substance becomes saturated with water, it is said to be hydrated. A salt that becomes hydrated is called an ionic hydrate. The forces holding the water molecules and crystal lattice together can either be hydrogen bonds, coordinate covalent bonds, or ion-dipole forces. Through heat, these bonds can be separated and the original salt can be recovered. In this experiment, an unknown ionic hydrate was heated in order break any bonds between water molecules and the salt’s crystal lattice to recover the original salt. Then when given the molar mass of the unknown salt, the ratio of H₂O to salt in the original hydrate was able to be figured out.

Experimental

An empty crucible was first heated with a Bunsen burner to get rid of any moisture that would add weight to the crucible. It was then placed in a desiccator to cool down, while not absorbing any moisture from the air. Once cool, the empty crucible was then weighed and the mass was recorded. Next 1 g of unknown ionic hydrate was placed into the crucible and this new mass was recorded. The crucible with ionic hydrate inside was then heated with its lid partially on for 20 minutes. The heat started off low and was steadily increased throughout the 20 minutes. The crucible and ionic hydrate were then allowed to cool in the desiccator. Once cool, they were weighed and this mass was recorded. The crucible and ionic hydrate were heated once again to remove any excess moisture left from the hydrate. The hydrate and crucible were cooled and weighed as before, and if its new mass was less than 0.003 g different than the previous weigh, it was considered to be completely free of water. The remaining product was the anhydrous salt.

Results

Identification code of unknown: B

Mass of empty crucible: 8.766 g

Mass of hydrate sample: 1.057 g

Mass of crucible plus sample before heating: 9.823 g

Mass of crucible and sample…

• After first heating and cooling: 9.674 g
• After second heating and cooling: 9.674 g

Mass of water lost: 0.149 g

Mass percent of water in sample: 14.1 %

Molar mass of anhydrous salt: 110. g/mol

Mass of anhydrous salt: 0.908 g

Number of moles of anhydrous salt remaining in the crucible: 0.00825 mol

Number of moles of water lost: 0.00827 mol

Average number of moles of water per mole of hydrate: 1 mol

Formula of hydrate: X ∙ H₂O

Calculations

In order to find the mass of the crucible and sample together, I simply added the mass of the empty crucible and mass of the hydrate alone. To find the mass of water lost, I subtracted the mass of the crucible and sample after the second heating from the mass of the crucible and sample before heating. In order to find the mass percent of water in the sample, I divided the mass of water lost (0.149 g) by the original mass of the hydrate sample (1.057 g) and then multiplied that answer by 100 to find the percent. To find the mass of anhydrous salt, I subtracted the mass of water lost from the mass of the hydrate sample. To find the number of moles of anhydrous salt remaining in the crucible, I took the mass of anhydrous salt (0.908 g) and divided that by its molar mass (110. g/mol). I performed that same operation to find the number of moles of water lost using a molar mass of 18.01528 g/mol for H₂O. Lastly, to find the number of moles of water per mole of hydrate, I divided the number of moles of anhydrous salt remaining by itself and by the number of moles of water lost. This came out to a 1:1.002 ratio, which is very close to 1:1.

Discussion/Conclusions

My final equation for my hydrate came out to almost exactly a whole number ratio. This could mean I performed the experiment very well, or that I simply got lucky and my numbers ended up coming out even. There is no way for me to check this because I don’t know the formula of the anhydrous salt, which would tell me what ionic hydrate it usually forms. If I knew the formula of the anhydrous salt, then I would be able to check my work and make sure my results came out correctly.

Overall, I think the experiment went smoothly. I was able to heat the crucible without turning it red, which could have caused some of the hydrate to burn away. I only had to reheat the crucible once before I got a constant mass. I did not have any trouble with that step, as I know some people did. Everything went as planned and I am fairly confident my formula is correct.

Introduction

When given an unknown substance, there are only a few ways to determine what it is. One way is to measure its density at a given temperature. Any pure substance has a specific density at a specific temperature. Density is defined as being equal to an object’s mass divided by its volume. The task for our lab was to determine the density of water and compare our recordings to the actual density of water listed in our lab packet. Then we were to find the density of an unknown liquid and find out what the substance was by matching its density with densities of substances listed in our packet.

Experimental

In order to find the density of water, one must know its mass and volume first. To find the water’s mass, we first weighed an empty Erlenmyer flask and rubber stopper. The rubber stopper was needed to insure no water would evaporate from the flask. This mass was recorded. The Erlenmyer flask was then filled with about 30 mL of deionized water dispensed from a buret. The flask and rubber stopper were reweighed, and the difference between the intial and final masses was the mass of the water. In order to find the volume of the water, I took note of the starting point of the water in the buret, then took note of the ending point of the water after about 30 mL were into the flask. That difference was the volume of water emptied into the flask. This process was performed three times in order to eliminate any error. Then the whole process was performed again unknown substance “Q” three times.

Results

Data for determination of the density of water:

Temperature of water: 19.5 °C

Average density of water: 0.9823 g/mL

Precision: 31.3544 ppt

Actual density of water (at 19.5 °C): 0.99834 g/mL

Error: 0.01604 g/mL

Data for determination of the density of an unknown liquid:

Temperature of unknown: 19.5 °C

Average density of unknown: 0.7816 g/mL

Precision: 1.6632 ppt

Unknown code: Q

Name of unknown: 2-propanol

Actual density of 2-propanol (at 20 °C): 0.786 g/mL

Error: 0.0044 g/mL

Calculations

In order to find the mass of the water and unknown, a simple subtraction problem was used. I simply subtracted the mass of the empty flask and rubber stopper from the mass of the full flask and rubber stopper. A sample equation would be 76.9994 g – 46.9959 g = 30.0035 g. This same method was used to find the volume of water in the flask. I subtracted the intial amount of liquid in the buret from the final amount of liquid in the buret. This difference was how much liquid was dispensed. An example would be 31.75 mL – 1.325 mL = 30.425 mL.

In order to find the density, I simply divided the mass found by the volume found. For example, 30.0035 g divided by 30.425 mL equals 0.9861 g/mL. To find the average density, I added the three densities I found, then divided that total by three to find the average. The equation for the water was (0.9861 g/mL + 0.9958 g/mL + 0.9650 g/mL) / 3 = 0.9823 g/mL.

Precision was found by taking the absolute value of the highest density minus the lowest density, dividing that difference by the average density, and then multiplying that answer by 1000. For example, the precision for the water was found by this equation: |(0.9958 g/mL – 0.9650 g/mL)| / 0.9823 g/mL x 1000. This gave me an answer of 31.3544 ppt (parts per thousand).

Finally to find the error, I found the absoulte value of my measured density minus the actual density. With my data, my equation for the water was |0.9823 g/mL – 0.99834 g/mL| = 0.01604 g/mL.

Discussion/Conclusions

My results for water turned out fairly well. My accuracy was very high, but my precision was not quite as good. A precision of 31.3544 ppt is a lot higher than 4 ppt, which is what is typically required to make sure my measurements were precise. However, my accuracy turned out to be very high, as my error was very low. It seems that I was lucky to have gotten such good accuracy with bad precision.

My data from the unknown substance turned out incredibly well. My precision was 1.6632 ppt, which is well under 4 ppt which is typically required. I assume 0 ppt would be perfect precision, so 1.6632 ppt is very good. My accuracy was also high, as my error was only 0.0044 g/mL. I don’t think I could have done the procedure much better than that.

Some of my error can be accounted for by a leak in my buret. A few drops of the liquid inside seemed to drip out from right above the bottom where it was supposed to come out. Also, I may have gotten finger prints on the flask, which would have added a slight bit of extra weight that could throw my calculations off. Lastly, the density given for my unknown was listed at 20 °C, but I measured the room temperature to be 19.5 °C. Therefore, I should be even closer to the actual density. For the water, I took the average of the density of water at 19 °C and 20 °C to find its density at 19.5 °C, but that may be incorrect if the density follows a curve. In the end, my data was fairly accurate with the actual data, so the experment was a success. My results showed that density is really equal to a substance’s mass divided by its volume.

Table I

Table II

Table III

Table IV

As each egg size got bigger, its measurements did indeed get bigger (Table I). For example, none of the measurements for the large eggs were smaller than the measurements for the medium eggs (Table I). The two eggs measured for each size were each about the same length, width, and mass. Their measurements only differed by at most 1.65 mm in length, 0.74 mm in width, and 2.5 g in mass (Table II). The greatest factor is separating the different eggs sizes was mass. The average masses for the two eggs measured for each size differed the most between egg sizes than their lengths or widths (Table IV).

A half dozen eggs were distributed to each team. The six eggs consisted of two medium sized eggs, two large sized eggs, and two extra large sized eggs. Each egg was labeled with a number and letter in order to keep track of it. Upon being distributed, the eggs were measured with a digital caliper to find their lengths and widths to the nearest hundreth millimeter. The lengths and widths recorded were the largest lengths and widths found. After dimensions were taken, the eggs were then weighed on a digital top loading scale. The weights were recorded in grams to the nearest tenth. The class’ data was then entered into a spreadsheet on the computer and the lab was completed.

Monday

9:00-9:50 AM, Applied Statistics (Section 103), Barbelin 221

11:00-11:50 AM, Biology I: Cells, Science Center 109

12:00-12:50 PM, First Year Italian I (Section 104), Bellermine 217

1:00-1:50 PM, General Chemistry Honors I, Science Center 300

2:30-5:30 PM, Bio I: Cells Lab (Section 101), Science Center 212

Tuesday

10:00-11:15 AM, Craft of Language (Section 139), Bellermine 117

11:30-12:30 PM, Biology SI Session, Science Center 100A

1:00-1:50 PM, General Chemistry Honors I, Science Center 300

6:00-9:45 PM, General Chemistry Lab I (Section 109), Science Center 409

Wednesday

9:00-9:50 AM, Applied Statistics (Section 103), Barbelin 221

11:00-11:50 AM, Biology I: Cells, Science Center 109

12:00-12:50 PM, First Year Italian I (Section 104), Bellermine 217

1:00-1:50 PM, General Chemistry Honors I, Science Center 300

Thursday

10:00-11:15 AM, Craft of Language (Section 139), Bellermine 117

6:15-7:15 PM, Biology SI Session, Science Center 303A

Friday

9:00-9:50 AM, Applied Statistics (Section 103), Barbelin 221

11:00-11:50 AM, Biology I: Cells, Science Center 109

12:00-12:50 PM, First Year Italian I (Section 104), Bellermine 217

1:00-1:50 PM, General Chemistry Honors I, Science Center 300

2:00-2:50 PM, First Year Italian I, Bellermine 312

When I was a young boy in elementary school first being taught to write, my teachers gave me only a few guidelines to follow when composing a story. First, I had to have an introduction, which set the stage for my story by letting the reader know what they were going to be reading about. Next, I needed to have a conclusion to put an end to my story, and lastly, each paragraph needed to have at least five sentences. The shape of the rest of the paper was up to me. This writing style was fairly easy for me to obey. Once I got past the introduction, I was off to the races; my stories unraveled as fast as my pencil could go. I would only hit a snag if I noticed a paragraph only had four sentences, but that was easily fixed by adding a three word sentence to the end. Only when I arrived at the end of my story would I have trouble again. Everything in the middle was free, I had total control to determine how my story grew.

Then I began middle school. In sixth grade English class, I was taught a few more rules that my teachers in elementary school “forgot” to tell me. Like before, every composition was to have an introduction, conclusion, and each paragraph needed to have at least five sentences. The big change was that now, I could only have three middle paragraphs, and these three paragraphs had to be solely about one point that related to a main point in my introduction called a “thesis”. My freedom was gone. My papers were now birds without wings, they could only go so far. At first it was very difficult for me to write in this style, but being the methodical person I am, I got used to it. All I really needed was to come up with three points that would relate to my thesis, and then add details to those points. Coming up with my three points and thesis proved difficult at times, however. In elementary school, the rules set before me for writing allowed for anything to happen, so it wasn’t necessary to plan ahead when writing a story, all I needed was one idea. Now I needed not just one main idea, but three other ideas that supported it.

When starting a paper, I often spent time writing my first sentence sentence, thinking it sounds bad, deleting it, and then trying again. I needed to have the perfect opening sentence to begin my essay. It seemed like every sentence would now be important and scrutinized for content. Why else would I be required to write a paper with exactly five paragraphs? Every line had to have been significant. I spent many hours working on the perfect introductory paragraph, and if I got too frustrated, I abruptly ended it with my thesis. Next I had to write about one of my three ideas that would relate to my thesis, but after putting so much effort into my introduction, how could I possibly write not one, not two, but three solid paragraphs with separate ideas all relating to my subject? I could usually manage getting through my second and third paragraphs, but when I arrived at my fourth paragraph, I would be fresh out of information to use that would support my thesis. I had used all my good ideas in the second and third paragraphs of my paper. The fourth paragraph of my paper was usually weak and looked like it didn’t belong, but I needed to have five paragraphs, so it stayed. After spending so much effort conforming my paper to the rigid guidelines set before me, I would simply change a few words from the introduction and use it as my conclusion. My teachers seemed to be fine with this, as the conclusion was just supposed to restate all my main points, which were included in my introduction.

I used this writing style all through my middle school and high school careers. Every writing assignment, the same old same old. Through all those years of writing, I became well acquainted to the five paragraph essay, but I never felt like I could easily write one. It always took me a good hunk of time to come up with a thesis and three supporting ideas, and then writing the paper itself always gave me trouble because I was bad at elaborating on my ideas. Though it was difficult for me to compose, it was the only way I knew how to write. I couldn’t write a paper any other way, I needed to have five paragraphs including an introduction, supporting paragraphs, and a conclusion. It wouldn’t feel right if I tried writing in a different manner. Writing any other way would be like a guy joining a field hockey team. There is no rule or law against it, but it doesn’t feel right.

I continued this train of thought in all my writing until this summer when I started played saxophone in a band with some friends. I had wanted to be in a band for a while, so desperately wanted this band to work out and hopefully have a few gigs before the summer was over. All the members of the band were good at their instruments, but our singer was horrible at writing lyrics. He wrote the words one song which were about going to the zoo and killing pandas. Needless to say, I knew that if this band was going to go anywhere, I would need to write lyrics myself. I had never written lyrics before, but I didn’t think it would be that hard, as writing notes for the saxophone was fairly easy for me. The two mediums, the saxophone and pencil, couldn’t be that different, could they? One day I sat down to write lyrics to a song and I just sat there blank for about thirty minutes. I had no idea how I was supposed to go about starting a song. In school I was always given an essay topic to write about and I was told how my essay was supposed to be structured. Now it was up to me to choose my essay topic, and it was up to me to decide how my essay was going to be structured. It took me days before I could think of something to write about and how to structure my song, but once I did it was like the Berlin wall coming down. My first song was very primitive and plain, but it opened up my ability to write creatively, which I hadn’t done since I was in elementary school. I began to come up with new ideas for lyrics at ease. Often I would get an inspiration from a rhythm and write a few good lines, then come back later and fill in the rest. The lyrics I wrote could start in different parts of a song. Sometimes I would begin with the beginning, but other times I started with the chorus or even a verse.

The way I wrote lyrics totally differed from the way a wrote papers in school. They could start anywhere, be about anything, could rhyme, could not rhyme, or follow any kind of pattern. I would start writing them whenever I had an inspiration, as opposed to in school when I was told when to begin writing. The only part of writing lyrics I have found difficult is finishing them. Once I have created a pattern or rhyming scheme to a song, it becomes tedious to finish the last few lines because I’ve created a structure I need to follow. The first few lines I create are pure inspiration, but the last few are usually lines I need to complete the song. Unfortunately, it’s necessary to write those last few words to the song, or else it would be unfinished and it wouldn’t be something that people would want to listen to. It is important to polish any song I write because when I let my thoughts flow, sometimes a few less than stellar ideas come out and they need to be revised. This is a boring mundane process that has to be done to get my ideas and messages across as clear as possible. This process that I now go through is much like Peter Elbow’s ideas of first-order and second-order thinking.

Elbow says that there are two different ways to think about your writing process, first-order and second-thinking. First-order thinking is what Elbow describes as being “intuitive and creative and doesn’t strive for conscious direction or control.” It is an uncensored type of writing process in which the writer simply writes whatever comes to them. Spontaneity and creativity define this writing style. “We use it when we get hunches or see gestalts,” says Elbow. In order to truly write with passion, Elbow says we must use first-order thinking to get our ideas down, regardless whether they make total sense or not. Carelessness takes a front seat over control in first-order thinking.

In second-order thinking, consciousness is crucial. It is necessary to know the direction of the writing and what kind of structure it is going to follow. Grammar plays a big role in second-order thinking, when in the case of first-order thinking, it is an afterthought. When describing second-order thinking, Elbow says, “We steer; we scrutinize each link in the chain. Second-order thinking is committed to accuracy and strives for logic and control: we examine our premises and asses the validity of each inference.” While this ordered type of writing may seem best suited for writing something like an essay for school, this is not necessarily the case.

Elbow says that, “second-order thinking often brings our people’s worst thinking.” When we strive for structure and organization, we make it more difficult to think freely and have an open mind with ideas. We tend to filter thoughts out before we even write them down because they may not fit perfectly within a paper’s format. So does this mean we should write solely with first-order thinking in mind? First-order thinking is what gets our ideas and thoughts down on paper, but it can often be a string of incoherent sentences. Elbow believes that we need to use both first-order and second-order thinking when we write. First-order should be used when beginning to write a composition in order to get any and all ideas down on paper. Once we have expunged our brains of any notions for our paper, we must go back and retool. Second-order thinking lets us fix our grammatic mistakes, revise any unclear points, and overall make our paper understandable to other people. The use of both first-order and second-order writing is what really allows us to get our best ideas through to other people.

I wholeheartedly agree with Elbow, especially when it comes to my process of writing lyrics. I must start out writing what comes to my mind; I can’t filter what I think about or else my creative drive will go away. If I think too much about what I’m writing, I start to go back and edit my lyrics when there are still more in my head, I may forget the ones I had in my head or decide they don’t work with the edits I had just made. I must use first-order thinking when writing songs, it is the only way for me to get my ideas out. Once I have emptied my mind of inspiration, I will go back over my lyrics and make sure they make sense, have the right amount of syllables, have the right rhyming scheme, and have the right form. If were to present my raw lyrics as a finished product, they would make no sense to an outside party. Once I revise them, they become something that anyone can understand and appreciate. Second-order thinking is needed in my writing process to make sure my thoughts are coherent. Without first-order thinking, I my best ideas would not come out on paper in the first place and without second-order thinking, they would not be comprehensible. Through the use of both, I am able to express any ideas, thoughts, and beliefs in a professional manner.