Dentist Essay Example For Students

Dental specialist Essay The Trip to the Dentist OfficeThinking to myself, is there any way I could shock back in my vehicle and head back for home, I enter the tall dainty tan shaded block building and stroll over to the lift, trusting that the last half hour of scouring my teeth to death pays off. Anxiously, I press the up button and calmly pause. The lift entryway instantly opens and I am immersed, the entryway closes, up I go. Once on the subsequent floor, I leave the lift and promptly I can smell the blend of the wintergreen enhanced tooth glue and the mind-boggling fragrance of dye out in the corridor, alongside the sound of the teeth crushing drills which gives, not, at this point the sentiment of the dental specialist office however of street development zone. With the opening of the external entryway, the impact of cool air hits me giving a sentiment of being stripped neglected ruthless winter. I stroll in and add my name to the rundown on the long sign in sheet. Andrew, the thin silver haired lady behind the winter white iridescent glass slide window, sees me and tells me that the dental specialist will be prepared in a brief moment. While I stand by reluctantly for the dental collaborator in her fresh perfect creme shaded uniform to report my name, I take a gander at the little tropical turquoise sprinkled fish in the enormous completely clear tank sitting toward the side of the room. The smooth quiet fish dart about playing find the stowaway with the plastic mermaid figure indented profound at the base of the tank with the gems of the ocean. While the small silver air pockets nimbly slip to the highest point of the tanks surface and break quietly while I sit tight. At that point I turn and hope to see a photograph collection sitting on an antiquated looking end table. I get it just to see mouthfulls of despairing rotting teeth and gums. I rapidly close the book thinking in the event that I saw it long enough I would go to stone and screen at the idea, however glad to realize that mine are all there gleaming in the wealth of daylight that is cresting in from the outside world through the streak free window. At l ong last, the medical attendant calls my name and I enter the inward office and sit in the cream hued trap looking seat, trusting that it will swallow me and send me anyplace however here. Taking a gander at all of the glossy treated steel apparatuses gives me an inclination that I am going to enter war. Setting out the brilliant overhead light immediately blinds me, at that point he begins the method. All in all, how have things been going with you since the last time Ive seen you Andy? he inquires. Auuuuuuhhhhh right. Is everything I could answer with. He chuckles and keeps on cleaning, clean, scratch, and floss. Spit in to this cup. He orders. With inclining my head forward and spit into the cup was simply unthinkable with the overwhelming lead cover set over me. I thought I had prevailing in that little undertaking yet as I rested my head down on the seat I could feel some quickly running down the side of my mouth. Okay Andy you are done, allowed to go! he said cheerfully. I was reluctant to ask however it would eat at me on the off chance that I didnt know now before he would call my folks to set up another incrushiating arrangement. Do I have any cavities, Dr. Schall? anxiously I inquired. No, you are sans cavity keep doing awesome. He at that point gives me another delicate tip toothbrush and I leave the dental specialist office with a considerably more joyful grin all over, while I turn my tongue over my silvery whites.

How nutrition relates to bone health Research Paper

How nourishment identifies with bone wellbeing - Research Paper Example The accompanying examination will assist the peruser with understanding the key structure hinders that are required by the body so as to perform and keep up a solid skeletal framework. Right off the bat, and most clearly, calcium just as nutrient K and nutrient D are the most essential and significant structure squares of legitimate bone quality and sustenance. Despite the fact that calcium is what is basically engaged upon concerning keeping up appropriate bone thickness and wellbeing, both nutrient K and nutrient D help to control the degrees of calcium in the circulatory system just as to support and debilitate how this calcium is integrated inside the bone marrow itself (Marian 440). In spite of the fact that this nutrient and supplement are frequently referenced at the same time with bone wellbeing and sustenance, scarcely any people comprehend the procedures that every one of these play in legitimate bone wellbeing. Right off the bat, nutrient D is changed over to what is known as calcidiol in the liver. When this change has occurred, the calcidiol is then siphoned through the circulatory system with the sole aim of looking to control the degrees of calcium a nd phosphate that exist in the circulatory system. Calcidiol acts thusly as a hormone to control levels of exacerbates that exist all through the body (Price 143). By acting in this administrative style, the body can utilize the calcium and phosphate levels that are in the circulation system so as to appropriately construct solid bones. Similarly, nutrient K assists with controlling the degree of calcium restricting that happens inside the bone structure. Moreover, notwithstanding calcium and nutrient K, D, the body needs to keep up satisfactory degrees of magnesium; the second most abundant mineral, after calcium, in the skeleton. Magnesium has a large group of uses as for bone wellbeing; in any case, for the reasons for this concise investigation it can comprehended to have a direct and significantly significant impact on the boney framework that assists with giving bones their thickness and

Where are you going with this

Where are you going with this My Mets are seriously kicking some you-know-what lately. I love it. Omar Minaya is my hero. =D Simone said: now that freshman year is over, how would you describe your first year at mit? relieved that youre still alive, dying for fall semester to start? from hearing about how hard mit is as a prefrosh, to a rising sophomore whose gone through all the goods and bads of freshman year, what do you have to say about mit now? also, just out of curiosity, and its totally okay i you dont feel comfortable talking about it, but whats your grade like so far at mit (1st and 2nd semester, assuming there wasnt pass/no record)? and what was your grade like back in high school? for example, were you a straight a student in high school and getting straight bs here at mit? Well now you did it. I guess now is as good a time as any to ponder the intricacies of my freshman year. How do I feel about freshman year being over? A little sad, actually. I enjoyed being a freshmen. I remember freshman year of high school complaining about bio objectives (weekly bio homework) and biosystem presentations- staples of freshman year at my small, close-knit high school. But then of course, once you became a sophomore it was all, Aww, the freshmen are doing bio objectives! and you immediately got all nostalgic because you thought you were so cool now that you werent at the bottom of the social food chain. You get what Im saying, right? Well anyway, I resolved to appreciate my freshman year of college as much as possible, and I really took that to heart. Freshman year is kind of a bonding experience, because youre all going through the motions of calculus psets (everyones got to do them but at the same time, youre all thinking pass/no record, God bless pass/no record), and theres nothing quite like it. Next year Ill be taking smaller, specialized classes in the major I hav ent chosen yet, and things will be very different. Of course, itll be cool to be done with non-applied math (*sigh of relief*). In terms of how hard it was, thats a tough question. Theres a lot of work, and some of it is really hard. As for me, I procrastinate far too much. Ill never be as productive as Mollie, for example. I read her blog and Im like what?! shehow does sheI dont get it. I personally think Im a little too ADD for straight up productivity. I have a hundred interests and Im always running around trying to join some new club or put together some random project or something. In high school, this was great. I got straight As in high school and had a blast doing all of my random energetic projects. Here, it kind of gets in the way of me having the work ethic to just sit down and finish that %[emailprotected] pset already. So first, just a little note about GPAs- you wont have one until youre a rising sophomore. Since first semester is graded as pass/no record, no GPA is calculated. Which makes sense, you cant have a grade point average until youhave grades. And that wont happen until the end of your freshman year. That said, my GPA is a 3.8. When I tell my friends, I think Ill just leave it at that. But in the interest of full disclosure to you guys, I should mention that at MIT, GPAs are on a 5.0 scale. *grin* Let me sidetrack for a minute. For as long as I can remember, I was one of the smartest kids in my class. Sometimes this was kind of cool. Sometimes this was not so cool. Do I really need to explain this? If youre reading this, you probably get it all too well. Then I went to a selective public magnet high school, and I figured that once I was mixed in with some of the smartest kids in my county, I wouldnt be a straight A student anymore. Only that didnt happen. I was still one of the smartest kids in the class. Im not complaining, I liked my straight As. And I like being smart. But after awhile, I was getting really sick of it. People were always coming to me for help (which was annoying), or bragging about me (which was awkward), or expecting me to always ace tests (which was stressful). So then, I got into MIT, and I thought, OK, NOW I wont be the smartest kid in the class, and this time I was right. *grin* And you know what? I love it this way. I probably shouldnt announce this on the internet of all things, but my personal academic goal for MIT is to pull off a cummulative 4.0 GPA- a B average. (I say I shouldnt say this because now Im on record saying it, and every prospective student and their parents will know if I fail at said goal, but oh well. *grin*) Anyway, like I said, I dont really have the best work ethic, but Im sure I could pull better grades if I really tried. The thing is, I dont really want to. Wait, dont judge- Im not done yet. Its kind of the same logic I used when I decided not to double major. Sure I probably could pull it off if I really wanted to- but I play field hockey and Im going to get a job and I volunteer on the ambulance andthere are so, so many other aspects of my life that are really important to me, and Im not going to sacrifice them in order to pull my GPA up a few points. Bs are fine with me. Of course, if I start failing everything, Ill have to drop a few extracirriculars. But in the meantime, I dont think academics is the absolute most important thing in my life. Sure its a priority, but Im living and learning and getting a lot out of other things too- things I cant get out of a book. On that note, I also spent this year cycling through clubs. I tried out a bunch of activities, and I was always evaluating how I felt about them. I had a lot of fun being super busy this year and I dont regret a single minute I spent on anything. (Except maybe calc psets. =P) But in some cases I didnt make strong connections with the people I was working with, or I didnt really feel passionate about what I was doing. So Im glad I had some experience with different things, and next year Im going to go try a bunch of completely different things instead. I have a feeling this is going to be a pattern, and I dont mind it at all. There are just too many things I want to try. Besides, Im sure along the way Ill run into some activities I really love to do that Ill dedicate insane amounts of my time and soul to. Does that answer your question? =P The other day I went out to eat with my friend Tetty. You remember Tetty, shes the one who hosted that gingerbread house making party where I exposed my true inner nerd. Anyway, I was wearing my favorite new shirt, and as soon as I got out of the car I said, You know you love my shirt. Thank you, ThinkGeek.com! Well, at first Tetty pretended to be mortified to be seen in public with someone wearing that shirt. (As a side note, its really a horrible shirt to wear anywhere thats notI dont know, MIT for example. Whenever anyone asks you what it means, youre just like, OK, Im so not explaining quantum mechanics to you. Ive been toying with the idea of telling people that theyre lyrics to some obscure heavy metal song or something.) Anyway, Tetty soon revealed her own inner nerd. But she said, the probability that I read the front of your shirt is much greater than the probability that I read the back of the shirt, so I think the girl has a point. It seems like this detail would mess with the wave equation. Thoughts?

Essay on Vibrio cholerae, the Human Immune System, and...

Vibrio cholerae, the Human Immune System, and Vaccines Cholera remains a drastically severe disease, killing hundreds of people each outbreak. When ingested, it attaches to the mucosal lining of the intestines and disrupts the normal flow of ions so that there is more sodium, chloride, and water in the intestinal lumen than normal and results in massive diarrhea. Cholera has made a global impact and been endemic in almost all parts of the world. Cholera control strongly emphasizes sanitation, clean drinking water, isolation, and careful food preparation. Two ways our body works against cholera as a self-limiting disease are sloughing cells and the secretory immunoglobulin (sIgA) antibody produced by mucus throughout our body. There are†¦show more content†¦Although the mucosa itself does not appear to be damaged by CT, the net flow of Na+ into tissue is decreased and the net flow of Cl- and water out of tissue is increased so as a result, there is more Na+, Cl-, and water in the lumen than there should be. This leads to massive diarrhea and great electrolyte imbalance. A patient with severe cholera can lose up to 20L of water a day (Salyers A., Abigail, 141). At times, diarrhea becomes so dilute it is almost clear, containing flecks of mucus that it is called rice water stool because of its watery consistency (Salyers A., Abigail, 142). This rapid rate of water loss and dehydration is tremendously fatal. At its most extreme, symptoms emerge in 3-4 hours, previously healthy patients can die within 6-8 hours of infection, and more commonly go into shock 6-12 hours after infection and die within 18 hours (Weekly Epidemiological Record, 6). Cholera’s level of severity is very life threatening and remains a big problem even in our world today. Almost 100 countries worldwide are still affected by cholera and it’s virtually impossible to completely prevent an outbreak. If left alone, this rapidly infectious disease can cause many fatalities. However, improved methods for surveillance, diagnosis, an d treatment, paired with higher standards of sanitation and personalShow MoreRelatedVibrio cholerae1286 Words   |  6 PagesIntroduction to Microbiology Pathogen paper Vibrio cholera Nazarbayev University Taxonomy and Morphology Vibrio cholerae is a gram-negative bacterium which is causative agent for the diarrheal disease cholera. Vibrio cholerae is a member of the Vibrionaceae family, which is a facultative anaerobic and is capable of respiratory and fermentative metabolism. It does not form spores and its motility is due to the single polar flagellum. Vibrios are highly halophylic and are very sensitiveRead MoreHow do bacteria affect human lives926 Words   |  4 Pagesï » ¿How do bacteria affect human lives? Bacteria interact and are a constant in our day to day lives, perhaps more than suspected. Bacteria are often thought of as bad, however this is untrue, there is also many types of ‘good’ bacteria. ‘Good’ bacteria can benefit us by simply helping our digestive system work and helping us in the process of fermentation. Bacteria are extremely helpful in the production of many things such as fuel and medicine. But bacteria directly affect our production ofRead MoreThe Effects Of Emotional Stress On The People Of Haiti Essay1474 Words   |  6 Pagesdisease such as cholera bacteria inflicting diarrhea. These infections are easily spread through contaminated water. Emotional stress which has a great impact on the physical as well as the mental health of the population quickly degraded the body immune system. Inadequate quantities and qualities of water to sustain health and personal hygiene, poor environmental sanitation and insufficient shelter are all factors that made cholera more potent. An infectious disease like cholera thrives best in a malnutritionRead MoreDisease is worldwide. Some, unfortunately, may continue to be a problem for decades or centuries to1500 Words   |  6 Pagesdisease that continues to disrupt parts of the world. Cholera is death by diarrhea (Symington, 2011). It is a poten tially severe disease that affects the digestive system, leading to extreme dehydration with the possibility of death within hours (Symington, 2011). The culprit responsible for this particular plague is the bacteria Vibrios cholerae (Kraft, 2010). Symptoms of cholera have been traced as far back as ancient Greek times and Sanskrit writings (Pukatzki Provenzano, 2013). Between 1817 andRead MoreCholera Is A Contagious Infection1808 Words   |  8 Pagesof inappropriate treatment modules. If the persons with severe symptoms tend to be treated appropriately, less than 1% of them would die from it. Vibrio Cholerae is the primary agent responsible for Cholera infection. An individual may be infected with the disease if he/she ingests food or water that is contaminated with the bacterium. Vibrio Cholerae has both the host and environmental stages for its life cycle. Looking at the organism’s structure, it is serologically differentiated into the O antigenRead MoreEscherichia Coli : A Type Of Intestinal Sickness1478 Words   |  6 Pagescreated by Vibrio cholerae. ETEC is endemic in numerous creating nations, including Mexico and Bangladesh, and is regularly experienced by travelers, individuals from the military, or different visitors travelling around. Due to poor surveillance, mortality because of ETEC is hard to gauge, yet there are accepted to be no less than 400,000 ETEC-related deaths in children less than 5 years old every year, with incalculable others likely grouped just as death because of diarrhea. Human ETEC strainsRead MoreThe Epidemic Of Vibrio Cholera1961 W ords   |  8 PagesVibrio cholera is a gram negative rod shaped bacteria which colonises the human gut causing acute diarrheal disease and leads to frequent epidemics around the world. In 2014 190, 549 cholera cases were reported to the World Health Organisation (Global Health Observatory Data 2014) , however the true number is likely to be far higher as there are many greatly affected locations which have poor or nonexistent data. Vibrio cholera is currently treated by the use of oral antibiotics coupled with rehydrationRead MoreEssay Cholera Disease Research Report2225 Words   |  9 PagesKarla Obasi HEA 341 Disease Research Report December 9, 2010 CHOLERA Disease Defined Cholera is an infection of the small intestine that causes a large amount of watery diarrhea. Cholera is a bacterial disease (caused by the bacterium Vibrio cholerae) usually spread through contaminated water. The bacteria, which are found in fecal-contaminated food and water and in raw or undercooked seafood, produce a toxin that affects the intestines causing diarrhea, vomiting, and severe fluid and electrolyteRead More Guillain-Barre Syndrome Essay1651 Words   |  7 PagesOf the individuals that contracted GBS following vaccinations, the swine flu vaccine of 1976-77 had the highest correlation rate. On a lesser note, five cases of GBS werereported following vaccinations with Haemophilus influenzas type b diphtheria toxoid-conjugate. Since 14 million doses of the vaccine have been distributed since June 1990, the incidence remains marginal. Experimental evidence linking GBS in humans with allergic neuritis in animals has attempted to show an immunologic basisRead MoreThe Health Issues That Are Still Affecting India Today2020 Words   |  9 PagesCholera is water borne and a communicable disease it is also preventable. This disease can cause people to have severe diarrhoea which the body then loses a mass amount of fluids, people then become exceedingly dehydrated which can lead to death. Vibrio cholera or V. Cholera is the bacteria found in Cholera infecting the intestines and causing diarrhoea (Cholera and the Thames, 2014). In 2014, The World Health Organisation (WHO) updated their fact sheet with key facts about Cholera. It was estimated

The Souls Of Black Folk - 1141 Words

When defining oneself race tends to stick out in the forefront of our minds. Race tends to separate one person from the next. The term race refers to people who have differences in biological traits that society feels are socially significant. Society’s emphasis on race has caused a seemingly unamendable division. People treat people differently because of their skin color. A person’s behaviors, actions and skin colors have been attributed to race. Skin color is the main factor when it comes to race. Ethnicity comes into play when people are being classified by nationality. Race is simply black or white, or simply light or dark, which plays into internalized or reverse racism. Personally I believe that African Americans struggle with race more than any other ethnicity because they struggle with both internal and external racism. W.E.B. Dubois as well as Glenn Loury spoke about the African American struggle in their works. W.E.B. DuBois wrote The Souls of Black Folk. In this work DuBois talks about life behind the shadow of race. In The Souls of Black Folk, DuBois makes several points about how as African Americans race is always at the forefront of our minds. It plays a role in everything we do as well as sometimes what we are able to achieve. He talks about how Blacks struggle with â€Å"double consciousness† which he also refers to as â€Å"twoness†. DuBois defines double consciousness as the, â€Å" †¦sense of always looking at one’s self through the eyes of others, of measuring one’sShow MoreRelatedThe Souls Of Black Folk1466 Words   |  6 Pagestitled The Souls of Black Folk in 1903 as a response to the condition of black people in America. The book predates the 1920s Harlem Renaissance, but can be viewed as a precursor to the New Negro Movement. Prior to 1903, blacks lived primarily in the South, but by the 1920s the black population in New York City rose by 115 percent. The movement of blacks from the South to the North occurred for various reasons; discontent with life in the Jim Crow South, widespread violence against blacks and theRead MoreThe Souls Of Black Folk938 Words   |  4 Pages The reading that I found most compelling to me was W.E.B DuBois excerpt titled â€Å"The Souls of Black Folk†. I find this reading compelling because DuBois was a huge advocate on togetherness and that people were being treated equal. During time that this reading was created, there were many obstacles African Americans were facing in that era that was not so promising for a bright future. The struggles they faced were, racial biasness, lack of representation and lack of educational attainment. DuBoisRead MoreThe Souls Of Black Folk1236 Words   |  5 Pagesmind. Du Bois argues in his book The Souls of Black Folk, that the gap between being black and American is far too wide. This is not an unjustified view especially in his time period, where laws were set in place purposely to prevent equality of the freedman. But even today, where those laws are no longer in place, a non-white American is too ethnic to be American and is simultaneously too American to be ethnic. Du Bois en tertains the idea of a Negro being both black and American but unfortunately hisRead MoreThe Souls of Black Folk1595 Words   |  7 Pagesthe text of The Souls of Black Folk embodies Du Bois experience of duality as well as his peoples. In Du Bois Forethought to his essay collection, The Souls of Black Folk, he entreats the reader to receive his book in an attempt to understand the world of African Americans—in effect the souls of black folk. Implicit in this appeal is the assumption that the author is capable of representing an entire people. This presumption comes out of Du Bois own dual nature as a black man who has livedRead MoreThe Souls Of Black Folk1048 Words   |  5 Pages The Souls of Black Folk is Written by W.E.B Du Bois and was published in 1903. This book is a collection of essays put together in a single book. Each essay is not the same, but revolve around the central idea of â€Å"the veil†. Another thought it revolves around is about segregation, and the lives of an average African American. The setting of this book takes place in the 19 20th century of the United States of America. Let me begin by explaining W.E.B Du Bois’s thinking of â€Å"the veil†. The veilRead MoreThe Souls Of Black Folk780 Words   |  4 PagesAfrica, in America and the islands of the sea† (W.E.B DuBois). This is part of the theme in the novel The Souls of Black Folk, which is based on an actual story/ autobiography of an African American leader, W.E.B DuBois. The narrator DuBois writes about race relations in the United Sates distributing the color-line. The color-line is the fundamental issue of racial conflict between the blacks and whites. It deals with the inequality and disparity of living in America as an African American. W.E.BRead MoreThe Souls Of Black Folks958 Words   |  4 PagesThe Souls of Black Folks â€Å"The Songs† The Songs sited in each chapter of this book was put together to deliberately guide the reader’s cerebration process in scrutinizing the context to identify with DuBois of how these events described effected Black people during this era in our history. Each example was directly associated with the subsequent chapter and solidified the arguments from DuBois’ perspective. It was translucently clear that the deliberate specimens of the song segments and the essaysRead MoreThe Souls Of Black Folk864 Words   |  4 Pagesabout a veil. However, the Merriam-Webster Dictionary offers another definition: â€Å"something that covers or hides something else.† I believe that this definition is more closely related to the veil that W.E.B. DuBois discusses in this book, â€Å"The Souls of Black Folk.† The first time Dubois brings up the idea of a veil, it is when he is describing an experience from his past that made him feel as though he was different from other pe ople. He uses the idea of a veil to emphasize separation he felt from theRead MoreThe Souls Of Black Folks1486 Words   |  6 Pagescertain knowledge, and we have people in our lives who fit into our unaware identity with us. Then, we have our aware life in which we know about the unsuspecting self and can look at things in a more critical way. Double-Consciousness In the Souls of Black Folks, DuBois writes about a ‘double consciousness . This term suggests African Americans perceive the world through two competing lenses. The first lens views the self as pushing forward from the social position of a marginalized other. TheRead MoreThe Black Music : The Soul Of Black Folk1855 Words   |  8 Pagespopular culture was created or directly influenced by Black music. Through the history of Black musical forms, each style represented a reality of the Black community, whether regionally or based on the time period and politics. Before enslaved Africans had the education to write their stories, they were told orally, often set to music. Highlighting the genius of a people, when there were ideas and stories that were adverse to those in power, Black people were able to hide their true messages in a

Nitrogen and Overall Cell Reaction Free Essays

Candidate session number 0 0 Examination code 8 8 1 1 – 6 1 0 5 Write your session number in the boxes above. Do not open this examination paper until instructed to do so. Section A: answer all questions. We will write a custom essay sample on Nitrogen and Overall Cell Reaction or any similar topic only for you Order Now Section B: answer one question. Write your answers in the boxes provided. 19 pages  © International Baccalaureate Organization 2011 0120 –2– SECTION A Answer all questions. Write your answers in the boxes provided. 1. N11/4/CHEMI/SP2/ENG/TZ0/XX Airbags are an important safety feature in vehicles. Sodium azide, potassium nitrate and silicondioxidehavebeenusedinonedesignofairbag. [Source:www. hilalairbag. net] Sodium azide, a toxic compound, undergoes the following decomposition reaction under certainconditions. 2NaN 3 (s) 2Na (s) + 3N 2 (g) Twostudentslookedatdatainasimulatedcomputer- asedexperimenttodeterminethevolume ofnitrogengeneratedinanairbag. (a) Sodium azide involves ionic bonding, and metallic bonding is present in sodium. Describeionicandmetallicbonding. How to cite Nitrogen and Overall Cell Reaction, Papers

Quantitative Analysis by Spectrophotometric Methods Essay Example

Quantitative Analysis by Spectrophotometric Methods Paper Abstract In this experiment, the absorbance of KMnO4 was measured by spectrophotometric method to determine the molar concentration and the molar extinction coefficient of KMnO4. In part 1, in order to determine the maximum absorbance wavelength of KMnO4, we measured the absorbance of the sample solution which contains KMnO4 at the wavelengths between 330nm and 660nm, and plotted the ? and A points; the ? max was 530nm. In part 2, the effect of concentration on the absorbance was examined. We prepared five differently concentrated (but, same path length) solutions, and measured the absorbance of them at the ? ax(530nm) discovered in part 1; According to the results, higher concentrated solution had higher absorbance value. The extinction coefficient(? ) could be calculated from the results determined in part 2 and Beer’s Law; ? = 1. 7 x 103. In part 3, the absorbance of the KMnO4 solution of unknown concentration was measured, and using Beer’s law and dilution equation, the initial concentration of the unknown was determined; The concentration of the solution (unknown # : 15) was calculated to be 3. 3 x 10-3M. Introduction Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled visible light. This visible light corresponds to a wavelength range of 400 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of seeing radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light. Figure 5. 1 The electromagnetic spectrum. Although visible light acts as a wave in some respects, it also displays properties characteristic of particles. The particle-like properties of visible light are exhibited through small, energy-bearing entities known as photons. The energy of a photon is: E photon = hc / ? (1) where h = Plancks constant, 6. 626 x 10-34 J/s, c = speed of light, 3. 00 x 108 m/s, and ? = wavelength of light. Light is energy, and when energy is absorbed by a chemical it results in a change in energy levels of the chemical. We will write a custom essay sample on Quantitative Analysis by Spectrophotometric Methods specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Quantitative Analysis by Spectrophotometric Methods specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Quantitative Analysis by Spectrophotometric Methods specifically for you FOR ONLY $16.38 $13.9/page Hire Writer Molecules normally exist in discrete energy levels. Vibrational energy levels exist because molecular bonds vibrate at specific frequencies. Electronic energy levels exist because electrons in molecules can be excited to discrete, higher energy orbitals. The energy (E) of light depends on its wavelength. Longer wavelengths (infrared) have less energy than shorter wavelengths (ultraviolet). A molecule will absorb energy (light) when the energy (or wavelength) exactly matches the energy difference between the two energy states of the molecule. In absorption, light — sunlight which is white light — strikes an object and part of the light may be absorbed by the object. The light we see coming from that object is the light which was not absorbed by the object. We see the not-absorbed light as the color of the object. If no light is absorbed, the object appears to be colorless. A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector. The beam of light consists of a stream of photons. When a photon encounters a molecule, there is a chance the molecule will absorb the photon. This absorption reduces the number of photons in the beam of light, thereby reducing the intensity of the light beam. The ratio of transmitted light intensity(I) to the incident light intensity(I0) is the transmittance, T: T = I / I0 (2) The amount of light a sample absorbs is affected by its concentration. If there are samples of same substances but different concentrations, the amount of the absorbed light will be different. In higher concentrated solution, more absorbing molecules are present in the path of the light, and the chance the light strikes the molecules will increase. So, more light will be absorbed by the sample; less light will be transmitted. In contrast, in lower concentrated solution, less light will be absorbed, and more light will be transmitted. The concentration is represented by the symbol C and is typically measured in mole/L. Another factor that affects the amount of light a sample absorbs is the path length which is the length of sample that the light passes through. The path length is represented by the symbol l and is typically measured in centimeters. When the light travels through longer distance, it will strike more absorbing molecules, so more light will be absorbed, and less light will be transmitted. The relationship of two factors (path length concentration) can be combined to yield a general equation called Beers Law. log10T = A = ? lC (3) The quantity ? is the molar absorptivity; in older literature it is sometimes called the molar extinction coefficient. It is the measure of how strongly a substance absorbs light at a particular wavelength; a larger extinction coefficient means that substance absorbs more light. The units of ? are usually in M-1cm-1 or L mol-1cm-1. A is the absorbance of light by a sample, and in this experiment, it was measured directly by a spectrophotometer. Experimental 1. Maximum Absorbance Wavelength: For the first part of this experiment, we determined the wavelength at which a selected substance (KMnO4) would absorb best. We obtained 10ml of 0. 0040M KMnO4, and using a graduated 1. 0-ml pipette and a pipetting bulb, transferred 1. 00ml of it into a 25. 0-ml volumetric flask. We filled the flask half full with deionized water, and added 1. 0ml of 3. 0M H2SO4. After mixing the contents, we filled the flask completely with deionized water and mixed them again. After the sample solution was prepared, we calibrated a spectrophotometer using a blank solution; in this experiment, deionized water was used for the bla nk solution because H2SO4 is transparent in the visible region. For measuring the absorbance of KMnO4, first we selected a wavelength, and placed a cuvette containing blank solution, then replaced it with the other cuvette containing the prepared KMnO4 solution. The absorbance was measured at the wavelengths between 360nm and 660nm, and each time a new wavelength was selected, the spectrophotometer was recalibrated. After all the absorbance values were measured, we plotted the absorbance data versus the wavelength to determine ? max which was used for the remainder of the experiment. 2. Standard Absorbance Curve: For the second part of this experiment, we examined the effect of varying the concentration on the absorbance. Five differently concentrated KMnO4 solutions were prepared for this part. For each 25. 00ml sample, 1. 00ml, 0. 80ml, 0. 60ml, 0. 40ml, and 0. 0ml of 0. 0040M KMnO4, 1. 0ml of 3. 0M H2SO4, and deionized water were added. The concentration of each solution was calculated using the dilution equation, M1V1 = M2V2. After a sample was prepared, we set the spectrophotometer to the ? max discovered in first part, calibrated using the blank, and then examined the absorbance of the sample. After all the findings were examined, we m ade a plot of the absorbance versus concentration. The molar extinction coefficient could be calculated using the Beer’s Law and the measured results. The inside diameter of the cuvette (path length) was measured with calipers. 3. Concentration of an Unknown: In the last part, we determined the concentration of unknown solution using the results (the path length and the extinction coefficient) determined in the second part. We obtained a solution of KMnO4 of unknown concentration. We followed the same procedure as for the second part to dilute the unknown solution; added KMnO4, H2SO4, and deionized water to make 25. 00ml sample, and calibrated the instrument with the blank solution at the ? max, and then measured the absorbance. The concentration of the unknown before it was diluted could be determined using the dilution equation in a reverse way. Results Discussion 1. Maximum Absorbance Wavelength: In part 1, we determined the sample’s absorbance spectrum to find the wavelength (? max) at which KMnO4 absorbs best. The absorbance data measured in this part is shown in Table 1, and Figure 1 is the absorbance spectrum constructed by plotting A vs ?. Table 1: Data for Maximum Absorbance Wavelength Wavelength360380400420440460480500 Absorbance0. 1450. 0770. 0210. 0080. 0170. 0510. 1320. 253 Wavelength520540560580600620640660 Absorbance0. 3620. 3600. 2460. 1130. 0400. 0300. 0220. 018 Figure 1: Absorbance Spectrum of KMnO4 According to the graph, ? max of KMnO4 is about 530nm, and it means that at the wavelength 530nm, KMnO4 absorbs light best. 2. Standard Absorbance Curve: In part 2, we examined the effect of varying the concentration on the absorbance. We prepared five differently concentrated solutions (the higher concentrated solution appeared darker pink-violet), and using dilution equation, the concentrations were calculated. Figure 2: Color of permanganate in different concentrated solution The calculated concentration and the measured absorbance of each solution are summarized in Table 2. Table 2: Data for Standard Absorbance Curve Volume (ml)Concentration (M)Absorbance 1. 001. 6 x 10-40. 320 0. 801. 3 x 10-40. 252 0. 609. 6 x 10-50. 185 0. 406. 4 x 10-50. 122 0. 203. 2 x 10-50. 057 As shown in Table 2, when concentration decreased, the absorbance value also decreased. A plot of the absorbance verses concentration (Figure 4) resulted a straight line, and according to the equation (3), the Beer’s Law, we knew that the slope(2036. 563) of the line equals ? l. The path length(l) of the cuvette was measured to be 1. 18cm, and the extinction coefficient(? ) at 530nm was calculated to be 1. x 103; The molar extinction coefficient varies with the wavelength of light used in the measurement. Figure 3: A plot of Absorbance vs. Concentration 3. Concentration of an Unknown: The concentration of the unknown (#15) solution was calculated using Beer’s Law and dilution equation. Table 3 shows the data gathered. Table 3: Data and Calculation for Unknown KMnO4 Concentrat ion TrialVol. of KMnO4 AbsorbanceCon. after dilution (M)Con. before dilution (M) 11. 0 ml0. 2511. 3 x 10-43. 3 x 10-3 20. 8 ml0. 2121. 1 x 10-43. 4 x 10-3 30. 6 ml0. 1557. 7 x 10-43. 3 x 10-3 The mean concentration before dilution was calculated to 3. x 10-3M. In part 1, the maximum wavelength of KMnO4 was found as 530nm. When MnO4- is dissolved in water, it appears pink-violet, and as shown in color wheel below, it absorbs primarily yellow-green light. (The color a substance appears to be is directly across the wheel from the color of light that substance has absorbed. ) The range of the wavelength of green-yellow light is between 495nm ~ 590nm, so the maximum wavelength measured (530nm) is reasonable. Figure 4: The Color Wheel The absorbance spectrum shows how the absorbance of light depends upon the wavelength of the light. The spectrum itself is a plot of absorbance vs. wavelength and is characterized by the wavelength (? max) at which the absorbance is the greatest. The value of ? max is important for several reasons. This wavelength is characteristic of each compound and provides information on the electronic structure of the analyte. In order to obtain the highest sensitivity and to minimize deviations from Beers Law, analytical measurements are made using light with a wavelength of ? max. In part 2, we observed that the absorbance was lower in less concentrated solution. Before the experiment was done, we expected that in lower concentrated solution, because fewer number of absorbing molecules would exist, so less light would be absorbed; the expectation was correct. As I mentioned above, the solution appears pink-violet because permanganate absorbs primarily green-yellow light. The pink-violet color was darker in higher concentrated solution as in figure 2, and it can be explained that more green-yellow light was absorbed, so the violet color appeared darker. In part 3, we measured the absorbance of diluted unknown KMnO4 solution to determine the concentration of it. I got the sample of unknown number 15. We’d already known the value of the path length and the extinction coefficient, so we could calculate the concentration using the Beer’s Law. The solution was diluted to 25ml, so, in order to determine the initial concentration of the unknown, we used the dilution equation in a reverse way. The absorbance of the unknown was similar to the absorbance of the known sample, so I expected that the concentration would be similar; the known concentration was 0. 0040M, and the unknown concentration determined to be 0. 0033M.