The links between CFCs Essay Example for Free

The links between CFCs Essay There have been many methods to try and investigate the chemistry of the atmosphere. Some scientists use monitoring to find out what is present in the atmosphere and in what concentration. Many of the substances present have characteristic absoroptions in the infra-red and ultra-violet reigons of the spectrum. (1) Eg Ozone absorbss ultra-violet radiation with wavelengths below 360nm. (1) Ozone concentration has to be measured over a period of time, at different heights and lattitudes to make sure that any decreases are not from natural influences. This can be done from the ground, high-altitude planes and satellites. Laboratory measurements are used to determine how substances will behave in the stratosphere like how they are affected by solar radiation and the rates of reaction. The rate constants are very important and allows the rate to be calculated for almost any conditions. It is not enough to know how they react in the laboratory because, on this small scale, gases mix quickly by diffusion (1) but in the stratosphere there are much larger distances and known gasses are not perfectly mixed. We would not be able to make full use of these measurements without knowledge of air movements (meteorology). CFCs in the troposphere are extremely unreactive but in the stratosphere there are much higher levels levels of radiation energy which are needed to break down C-Cl bonds. This energy does not reach the troposphere because it is filtered out by the O2 and O3 molecules present in the stratosphere. Small concentrations of CFC 11 (CCl3F) were discovered in rural areas, wel away from any sources,and showed that it was able to diffuse to Antarctica. Such a stable gas would accumulate in the atmosphere. Scientists flew into the ozone hole and measured the concentrations of ClO radicals and O3. Figure 4 below (1) shows that the concentration of O3 fell dramatically at the point where the concentration of ClO radicals soared. This was conclusive proof that a catalytic cycle involving Cl radicals must be involved in O3 depletion. Also figure 1 (4) shows a severe depletion in the ozone layer over the Antarctic on October 1, 1999. The rapid depletion of CFCs in the stratosphere is due to the high levels of ultra-violet radiation which leads to the photodissociation of CFC molecules. Eg A CFC 11 molecule would absorb the high energy ultra-violet radiation and fragment to release chlorine radicals: CCl3F == CCl2F + Cl. (1) The Cl radical could then destroy ozone in a catlytic cycle (1): Cl + O3 == ClO + O2 ClO + O == Cl + O2 overall: O + O3 == 2O2 (1) The chlorine atoms are not used up in these reactions, they are homogeneous catalysts. (4) The raction rate is fast and one chlorine molecule could destroy thousands of ozone molecules. The oxygen free radicals, O in the second equation, are formed continuosly in the stratosphere. Ozone depletion is most severe over Antartica in the southern spring because of unique weather conditions, the sun disappears for six months. In the winter a vortex of cold air isolates the circulating air mass from the rest of the atmosphere (1), polar stratospheric clouds form allowing particles nitric acid frozen around the nuclei of sulphuric acid. The clouds provide a surface for the reaction of HCl with ClONO2. This reaction produces Cl2 which breaks down to form Cl radicals when the sun returns. These radicals lead to the destruction of Ozone. Figure 5 below (1) shows how polar stratospheric clouds help Cl radicals to destroy ozone. As the chemistry of chlorine in the sratosphere is better understood it is shown that some gasses like NO2 and CH4 can react with ClO radicals and interrupt the catalytic cycle: Cl + CH4== HCl + CH3 ClO + NO2 == ClONO2 The chlorine atoms become bound up in the stable reservoir molcules, HCl and CIONO2. They remain chemically inactive until realeased (3). CFCs have been used so widely for many reasons. It has the essential physical properties for a refigerent, appropriate boiling and freezing points (low enough to evapourate efficiently but high enough to liquefy by compression) (2). Its chemically stable, non toxic and cheap. (2) CFCs and the related HCFCs quickly became the refrigerantschioce for almost all applications. It had a wide range of uses, see table 2 below(2), and it was better than all previous refigerants. Table 2 (2). Compound Number Bp/ C Major Applications CCl3F CFC11 23 Air conditioners, water chillers, aerosols, coolant CCl2F2 CFC12 -29 Domestic fridges and freezers, car air condtioning, poly(styene) foams Scientists want to use HFCs (hydrofluorocarbons) as a replacement for CFCs because they contain fluorine as the only halogen (2). They also do far less damage to stratospheric ozone because HFCs are broken down in the troposphere by OH radicals so very little reaches the stratosphere also the C-F bond is not broken in the stratosphere. HFCs have no effect on O3 but they contribute to global warming. Also existing equipment will have to be modified or redesigned which could be very expensive. References:- 1. Article 1 Do CFCs destroy the ozone layer? , taken from ChemistryReview, March 1993. 2. Article 2 The rise and fall of CFCs, taken from Chemistry Review, September 1996. 3. Chemical Ideas pg 242 Heinemann 4. http://www. cis. ohio-state. edu/hypertxt/faq/usenet/ozone-depletion/top. html.

Expeditions to Antarctica and Annapurna Essay -- Comparison, Shackleto

When taking a quick look at the two expeditions, one led by Ernest Shackleton to Antarctica and the other led by Arlene Blum to climb Annapurna, a quick summation can be made that Blum succeeded in her expedition and Shackleton failed. But this is a shallow view, not considering the nuances and actual experiences of the trips. Ernest Shackleton set out with his crew in 1915 to be the first expedition to cross Antarctica, but in fact, he never set foot on the continent. While failing at his initial goal, he was a highly successful leader and kept his 28 men safe for close to two years, while they were trapped on the ice floe and then, after the ice gave way, when they were paddling hundreds of miles across open seas in small, wooden lifeboats. He then completed the treacherous journey across South Georgia Island to reach a town and resources necessary to rescue his other men. All of his men were rescued alive and safe and all were able to return home to their families. In compar ison, Arlene Blum set out from the United States in 1978 with 9 of her teammates as the American Women's Himalayan Expedition – the first all-woman group to attempt to climb Annapurna. Though their expedition was too often hazardous, it didn’t have the same level of urgency, because at any point during their climb, the group was at liberty to descend. Blum struggled with her role as the leader of this group of highly independent women. She too often hesitated and showed her lack of confidence, which in turn led to many problems within the group and with the hired Sherpas. On October 15th, 1978, two members of the expedition, along with two Sherpas, reached the summit of Annapurna, fulfilling the goal of the group. However, two days later, on Octobe... ...ew to the path of being trapped by the ice, he excelled at his decision making. He didn’t believe that one should look back at past mistakes and waste time on regrets, indeed, â€Å"Shackleton never wasted time or energy lamenting things that had passed or that he couldn’t change (Morell, pp. 145).† As Shackleton himself said, â€Å"A man must shape himself to a new mark directly the old one goes to ground (Morell, pp. 145).† This ability to shift quickly and react to new circumstances served him and his crew members well and allowed all of them to save themselves from their icy trap. As Dennis Perkins says in his book, Leading at the Edge, in reference to the last leg of Shackleton’s expedition, â€Å"Their heroic journey across South Georgia Island had saved their shipmates. It remains a tribute to unremitting effort—and to the tenacious creativity at The Edge (pp. 148).† Expeditions to Antarctica and Annapurna Essay -- Comparison, Shackleto When taking a quick look at the two expeditions, one led by Ernest Shackleton to Antarctica and the other led by Arlene Blum to climb Annapurna, a quick summation can be made that Blum succeeded in her expedition and Shackleton failed. But this is a shallow view, not considering the nuances and actual experiences of the trips. Ernest Shackleton set out with his crew in 1915 to be the first expedition to cross Antarctica, but in fact, he never set foot on the continent. While failing at his initial goal, he was a highly successful leader and kept his 28 men safe for close to two years, while they were trapped on the ice floe and then, after the ice gave way, when they were paddling hundreds of miles across open seas in small, wooden lifeboats. He then completed the treacherous journey across South Georgia Island to reach a town and resources necessary to rescue his other men. All of his men were rescued alive and safe and all were able to return home to their families. In compar ison, Arlene Blum set out from the United States in 1978 with 9 of her teammates as the American Women's Himalayan Expedition – the first all-woman group to attempt to climb Annapurna. Though their expedition was too often hazardous, it didn’t have the same level of urgency, because at any point during their climb, the group was at liberty to descend. Blum struggled with her role as the leader of this group of highly independent women. She too often hesitated and showed her lack of confidence, which in turn led to many problems within the group and with the hired Sherpas. On October 15th, 1978, two members of the expedition, along with two Sherpas, reached the summit of Annapurna, fulfilling the goal of the group. However, two days later, on Octobe... ...ew to the path of being trapped by the ice, he excelled at his decision making. He didn’t believe that one should look back at past mistakes and waste time on regrets, indeed, â€Å"Shackleton never wasted time or energy lamenting things that had passed or that he couldn’t change (Morell, pp. 145).† As Shackleton himself said, â€Å"A man must shape himself to a new mark directly the old one goes to ground (Morell, pp. 145).† This ability to shift quickly and react to new circumstances served him and his crew members well and allowed all of them to save themselves from their icy trap. As Dennis Perkins says in his book, Leading at the Edge, in reference to the last leg of Shackleton’s expedition, â€Å"Their heroic journey across South Georgia Island had saved their shipmates. It remains a tribute to unremitting effort—and to the tenacious creativity at The Edge (pp. 148).†

History 108 †Early American History Essay

The quarrel between the British and the Americans lasted for less than three years. It began in 1812 and ended in 1825. When the war was through the side of the British lost approximately 1, 600 troops and the United States lost about 2, 260 of its troops. Ex US-president Madison declared war in order to protect US ships from being searched by both the British and the French. Some people believed the war to be a means of gaining US independence and protecting its honor from the disrespectful British. However, the war ended in a draw since both sides are not properly equipped for war. At the time of the Napoleonic war both French and British alike prohibited the existence of neutral trade. Even though the war between France and Britain had affected the American trade, the Americans still tried to remain neutral. However, the British did things which provoked the Americans especially when the British seized about 8, 000 US sailors. The British made it their business to impress American ships and employing people from the ship under the British navy. They tried to justify their actions by claiming that they are only getting the men under the rule of the monarchy. However, that particular statement of the British had been a lie for they have employed more than 6,000 of the American citizens under their services 1. The attack of the British vessel, Leopard on the US naval frigate Chesapeake resulted in a calamity and is one of the causes of the war. The Leopard demanded to search Chesapeake for British deserters, to which its captain, James Barron firmly denied the particular demand. This resulted in to an attack which killed lots of Americans. In response to the event, Jefferson banned the British from American waters and he also ordered that the British stop their search on American ships. Even though Great Britain apologized for their actions they still refused to give way to the demands of the United States 2. On June 18, 1812, war had been declared by the Americans to the British. The Americans had many reasons for declaring a war such as the seizing of American sailors by British vessels, the French and British restriction on neutral trade which greatly affected the US economy, and the military support of Great Britain on Native Americans in protecting their lands. Great Britain attempted to prevent the war by withdrawing their trade restrictions; however there is no turning back for the Americans especially since they already viewed that particular war as a war for their independence. However, there are other primary reason why the war still continued and it is the wish of the Western and Southern Americans to drive the British and the Spanish away from North America. However, as mentioned earlier, neither side is prepared for a war and it is the primary reason why the war ended in a draw. The British had most of its army on Peninsular War and they are very preoccupied with the Napoleonic war as well as their war against France. The United States on the other hand, are hard put by the fact that their military leaderships were weak. This particular weakness could be seen on the numerous attempts of the United States to infiltrate Canada. None of those attempts succeeded in spite of the fact that they had been fighting only a small British force. Another major problem which plagued Americans during their time is the minority of their financial and logistical resources. These had only been some of the reasons why neither the British nor the Americans won the war of 1812 To conclude, the war began because of the numerous abuses the Americans have had to suffer under the British navy as well as for the interest of the Americans to drive the British and the Spaniards away from Florida and North America. However, since neither force is ready for the said war, and since both sides are preoccupied by other major concerns the war ended in a stalemate. Reference: Henretta, James A. , David Brody, and Lynn Dumenil. America – a Concise History. Vol. 1 St. Martin’s Press, 2005. Microsoft Encarta Online Encyclopedia. â€Å"War of 1812. † (2007), http://encarta. msn. com/encyclopedia_761571913_1/War_of_1812. html.

How to Write a Character Analysis

Being mindful of subtle hints, like mood changes and reactions that might provide insight into your characters personality, can help you write a character analysis. Describe the Characters Personality We get to know the characters in our stories through the things they say, feel, and do. Its not as difficult as it may seem to figure out personality traits based on a characters thoughts and behaviors: Say cheese! the exasperated photographer shouted, as she pointed her camera toward the group of squirming children. Margot displayed her broadest, most convincing fake smile as she inched ever-closer to her younger cousin. Just as the photographers finger twitched over the shutter button, Margot leaned into her young cousins side and pinched hard. The boy let out a yelp, just as the camera clicked. You can probably make some assumptions about Margot from the brief segment above. If you had to name three character traits to describe her, what would they be? Is she a nice, innocent girl? Doesnt seem like it from this passage. From the brief paragraph, we can assume that shes apparently sneaky, mean, and deceptive. Determine the Character Type of Your Protagonist You will receive clues about personality through a characters words, actions, reactions, feelings, movements, thoughts, and mannerisms. Even a characters opinions can help you learn more about the individual, and you may discover that the person fits one of these stock character types: Flat character. A flat character has one or two personality traits that dont change. The flat character can play a major or a minor role.Round character. A round character has many complex traits; those traits develop and change in a story. A round character seems more real than a flat character because real people are complex.Stock or stereotype character. Stock characters are stereotypes, such as hot-tempered redheads, stingy businessmen, and absent-minded professors. They are often found in genre fiction (romance novels and mysteries, for example), and are usually flat characters. They are often used as a tool to move a plot forward.Static character. A static character never changes. A loud, obnoxious background character who remains the same throughout the story is static. A boring character who is never changed by events is also static.Dynamic character. Unlike a static character, a dynamic character does change and grow as the story unfolds. Dynamic characters respond to events and experience changes in attitude or outlook. The character might go through a transformation during the course of the storyline, and grow as a result of actions that took place. Define Your Characters Role in the Work Youre Analyzing When you write a character analysis, you must define that characters role. Identifying the character type and personality traits can help you better understand what the larger role of the character is within the story.  The character either plays a major role, as a central element to the story, or a minor role to support the major characters in the story. Protagonist. The protagonist of a story is another name for the main character. The plot revolves around the protagonist. There may even be more than one main character. In The Adventures of Huckleberry Finn, Huck Finn is the protagonist.In Little Red Riding Hood, the little girl is the protagonist. Antagonist. The antagonist is the character who represents a challenge or an obstacle to the protagonist in a story. In some stories, the antagonist is not a person but rather a larger entity or force that must be dealt with. In Little Red Riding Hood, the wolf is the antagonist.In The Adventures of Huckleberry Finn, society is the antagonist. Society, with its unfair laws and rules, represents the obstacle to Hucks development as a person. Foil. A foil is a character who provides contrast to the main character (protagonist), in order to emphasize the main characters traits. In A Christmas Carol, the kind nephew, Fred, is the foil to nasty Ebenezer Scrooge. Show Your Characters Development (Growth and Change) When you are asked to write a character analysis, you will be expected to explain how a character changes and grows. Most major characters go through some kind of significant growth  as a story unfolds, often a direct result of dealing with some sort of conflict. Notice, as you read, which main characters grow stronger, fall apart, develop new relationships, or discover new aspects of themselves. Make note of scenes in which character changes become apparent or the characters opinions on a topic change. Clues include phrases such as she suddenly realized that... or for the first time, he... Understanding the journey of your character and how it relates to the story as a whole can help you better understand that characters motives and better represent the person in your overall analysis. Article edited  by  Stacy Jagodowski