Monday, January 27, 2020
What Is A Buffer Biology Essay
What Is A Buffer Biology Essay A buffer is an aqueous solution that has a highly stable pH. If you add acid or base to a buffered solution, its pH will not change significantly. Similarly, adding water to a buffer or allowing water to evaporate will not change the pH of a buffer. A buffer is a substance in a solution that can neutralize either an acid or a base. A substance is said to be naturally buffered if it has a buffering action in its natural state .Buffers are used in chemistry to modulate and stabilize the pH of a solution. A buffered solution can be made in a variety of ways, most simply by creating a mixture of a weak acid and its conjugate base. Buffers are chemicals that, when added to water, tend to maintain a certain pH. This is due to the buffers ability to either accept or donate a proton (hydrogen ion, H+) or hydroxyl (OH-) to keep the pH in a certain range. Buffers are different than strong acids and bases because buffers do not donate all of their protons or hydroxyls within their buffering range. A buffer is a substance, usually a salt, that can bind with either the positively-charged hydrogen ion of an acid or the negatively-charged hydroxide ion of a base. If a solution is buffered, acids or bases can be added to the solution without changing its pH as drastically as if the acid or base were added to an unbuffered solution Natural Buffers A solution is said to be naturally buffered if it contains buffering compounds as it exists in nature. Blood is an example of a naturally buffered solution. Blood must maintain a pH close to 7.4 in order to carry oxygen effectively and contains compounds that react to acids or bases in order to neutralize them.  PREPERATION OF BUFFER A compound can buffer the pH of a solution only when its concentration is sufficient and when the pH of the solution is close (within about one pH unit) to its pKa. To make a buffer you must first pick a compound whose pKa  is close to the pH you want for the solution, and then decide what the buffer concentration should be. Typically, buffer concentrations are between 1 mM and 200 mM, depending on the desired ionic strength and the buffering capacity required. If the pH is expected to decrease during the experiment, choose a buffer with a pKa slightly below the working pH. Conversely, if the pH is expected to increase during the experiment, select a buffer with a pKa slightly above the working pH. Having decided on the total buffer concentration, you must adjust the ratio of the protonated and unprotonated forms of the buffer in your solution so as to give the desired pH. Typically, buffers are composed of weak acids and their salts, or w eak bases and their salts. If the protonated form is uncharged, it is an acid (like acetic acid), and its unprotonated form is a salt (e.g., sodium acetate). Conversely, if the unprotonated form is uncharged it is a base (like Tris base), and its protonated form is a salt (e.g., TrisHCl). Four practical ways to make a buffer are described below: The Slow and Stupid Method  To avoid adding extra salt to a solution, prepare a buffer composed of an acid and its salt by dissolving the acid form of the buffer in about ~60% of the water required for the final solution volume. Adjust the pH using a strong base, such as NaOH. When preparing a buffer composed of a base and its salt, start with the base form and adjust the pH with strong acid, such as HCl. After the pH is correct, dilute to just under the final solution volume. Check the pH and correct if necessary, then add water to the final volume. Advantages: Easy to understand. Disadvantages: Slow. May require lots of base (or acid). If the base (or acid) is concentrated, it is easy to overshoot the pH. If the base (or acid) is dilute, it is easy to overshoot the volume. Ionic strength will be unknown. Adding a strong acid or base can result in temperature changes, which will make pH readings inaccurate (due to its dependence to temperature) unless the solution is brought back to its initial temperature. (2)The Mentally Taxing Method  Using the buffer pKa , calculate the amounts (in moles) of acid/salt or base/salt present in the buffer at the desired pH. If both forms (i.e., the acid and the salt) are available, convert the amount required from moles to grams, using the molecular weight of that component, and the weigh out the correct amounts of both forms. If only one form is available, you can prepare the buffer by adding all of the buffer as one form, and then adding acid or base to convert some of the added buffer to the other form. Decide what the total concentration of buffer will be in the solution, and convert the concentration to amount (in moles) using the volume of solution, and then to grams, using the molecular weight of the buffer form available. Then calculate the amounts (in moles) of each form that will be present in the final solution, using the buffer pKa  and the desired pH.  Then calculate how much strong acid or base must be added to convert enough of the buffer form added to the other form, to give the correct amounts of each form at the pH of the final solution. Dissolve the buffer and strong acid or base in slightly less water than is required for the final solution volume. Check the pH and correct if necessary. Add water to the final volume. Advantages: Fast. Easy to prepare. Additional pH adjustment is rarely necessary, and when necessary, the adjustment is small. Ionic strength easily calculated. The Two Solution Method  Make separate solutions of the acid form and base form of the buffer, both solutions having the same buffer concentration (and ionic strength, if required) as the concentration of total buffer in the final solution. To obtain the desired pH, add one solution to the other while monitoring the pH with a pH meter. Advantages: Easy to do. Disadvantages: Requires both forms of buffer. The required solution volumes are proportional to the ratio of buffer components in the final solution at the desired final pH, so making equal amounts of each form may waste a lot of one solution. The Completely Mindless Method  Find a table of the correct amounts of acid/salt or base/salt required for different pHs, and dissolve the components in slightly less water than is required for the final solution volume. Check that the pH and correct if necessary. Add water to the final volume. Advantages: Easy to do (with appropriate table). Convenient for frequently prepared buffers. Disadvantages: May be impossible to find table. Table may be incorrect. Requires both forms of buffer. Component amounts from table will need to be adjusted to give the buffer concentration and volume in your solution. Ionic strength is unknown.  Common Buffer Preparations  Buffer Stock Soln Components Amount per Liter Soln. Conc. Stock Soln Final Conc.  PBS  (Phosphate Buffered Saline)  adj. pH ~7.3  10X NaCl  KCl  Na2HPO4ƒƒ-7H2O  KH2PO4  80 g  Â Â 2 g  Â 11.5 g  Â Â 2 g  1.37 M  Â Â 27 mM  Â Â 43 mM  Â Â 14 mM 137 mM  Â Â Â 2.7 mM  Â Â Â 4.3 mM  Â Â Â 1.4 Mm  SSC  adj. pH ~7.0  20X NaCl  Sodium citrate  175 g  Â Â 88 g  3 M  Â 0.3 M  150 mM  Â Â 15 Mm  STE (Saline Tris EDTA)  1X Tris base  NaCl  EDTA (acid)  1.2 g  Â 0.6 g  Â 0.29 g  10 mM  Â 10 mM  Â Â 1 mM  10 mM  Â 10 mM  Â Â 1 mM  TAE  (Tris acetate EDTA)  pH ~8.5  50X Tris base  Acetic acid (glacial)  EDTA  242 g  Â Â 57.1 mL  37.2 g  2 M (Tris acetate) 0.1 M   40 mM (Tris acetate)  Â Â 2 mM  TBE (Tris borate EDTA)  pH ~8.0  10X  Tris base  Â Boric acid  Â EDTA  108 g  Â Â 55 g  Â Â 40 mL (0.5 M pH 8)  0.89 M  Â 0.89 M  Â 0.02 M  89 mM  Â 89 mM  Â Â 2 mM  TE  (Tris EDTA)  pH ~7.5  1X Tris base  H2 EDTA (acid)  1.2 g  Â 0.29 g  10 mM  Â Â 1 mM Useful buffer mixtures Components pH range HCl, Sodium citrate 1 5 Citric acid, Sodium citrate 2.5 5.6 Acetic acid, Sodium acetate 3.7 5.6 K2HPO4, KH2PO4 5.8 8 [3] Na2HPO4, NaH2PO4 6 7.5 [4] Borax, Sodium hydroxide 9.2 11  Universal buffer mixtures By combining substances with pKa values differing by only two or less and adjusting the pH a wide-range of buffers can be obtained. Citric acid is a useful component of a buffer mixture because it has three pKa values, separated by less than two. The buffer range can be extended by adding other buffering agents. The following two-component mixtures (McIlvaines buffer solutions) have a buffer range of pH 3 to 8. 0.2M Na2HPO4 /mL 0.1M Citric Acid /Ml pH 20.55 79.45 3.0 38.55 61.45 4.0 51.50 48.50 5.0 63.15 36.85 6.0 82.35 17.65 7.0 97.25 2.75 8.0 A mixture containing citric acid, potassium dihydrogen phosphate, boric acid, and diethyl barbituric acid can be made to cover the pH range 2.6 to 12.[6] Other universal buffers are Carmody buffer and Britton-Robinson buffer, developed in 1931. Significance:- An important number for any aqueous solution is its pH. The pH is the negative logarithm of the concentration of hydrogen ions (often represented as a hydronium ion, which is a water molecule with an extra proton attached). Anything with a pH of less than 7 is considered to be acidic, and a solution that has a pH of greater than 7 is basic. Pure water, which has an equal amount of acid and base in it, is defined as having a pH of 7. Identification:- Buffered solutions are used to make a solution that exhibits very little change in its pH when small amounts of an acid or base are added to it. A buffer can be made by addition of a weak acid and its conjugate base to a solution. Alternately, a weak base and its conjugate acid can be used. Buffers are most effective when the amounts of the weak acid/base and the conjugate base/acid are usedgenerally to be effective, neither quantity should be more than 10 times that of the other. Control of ph by buffer Buffers are chemicals that, when added to water, tend to maintain a certain pH. This is due to the buffers ability to either accept or donate a proton (hydrogen ion, H+) or hydroxyl (OH-) to keep the pH in a certain range. Buffers are different than strong acids and bases because buffers do not donate all of their protons or hydroxyls within their buffering range. Background:- The measure of pH gives the concentration of hydrogen ions in a solution. Pure water has a pH of 7.0 and has an equal balance of hydrogen ions and hydroxyl ions. The pH will be lower if an acid is added and higher if a base is added. For various purposes, it is useful to add a buffer so that the pH remains constant even if an acid or base is added to the solution. Buffers are used to maintain constant pH. Buffer Equilibrium:- Different buffers work at different pHs. A buffer is most efficient at maintaining a constant pH when the pH equals its acid dissociation constant, its pKa. At this pH, the buffer consists of an equal solution of protonated and de-protonated conjugate base. This often denoted by a theoretical buffer molecule, AH, dissociating into a proton, H+, and the conjugate base, A-. The pKa is determined by the pH where the concentration of AH equals the concentration of A-. Buffering Acids:- At its pKa, a buffer can maintain a constant pH by accepting free protons. Adding an acid to the solution, such as HCl, will cause free protons to enter the solution. The conjugate base will accept the free protons, causing the pH to be unchanged. The solution will remain at the same pH as long as there is enough conjugate base to accept the additional protons. The reaction can be written as the dissolution of the acid: HCLH+ + Cl- leading to free H+ in the solution. The further reaction with the buffer occurs: H+ + A- HA. This removes the free protons and constant pH is maintained. Buffering Bases:- Adding a base such as sodium hydroxide to a solution will cause an increase in the hydroxyl concentration. In a buffered solution, the protons attached to the undissociated buffer are donated to the solution, forming H2O with the free hydroxyls. This counters the effect of the base and maintains the pH of the solution as long as there is undissociated buffer available in the solution. In this case, the reaction can be written as the dissolution of the base: NaOH Na+ + OH- leading to the second reaction of OH- + HA H2O + A-. Different Buffers:- Different buffers have different pKas and can be used to buffer solutions at a wide range of pHs. Chemicals used as buffers often have the ability to donate or accept multiple protons or bases. These buffers hence have two or more different pKas corresponding to how many protons or hydroxyls per molecule they can donate or accept. Different buffer molecules can be combined to form customized buffer ranges. For a list of biological buffers, see Resources. WORKING OF BUFFER When hydrogen ions are added to a buffer, they will be neutralized by the base in the buffer. Hydroxide ions will be neutralized by the acid. These neutralization reactions will not have much effect on the overall pH of the buffer solution. When you select an acid for a buffer solution, try to choose an acid that has a pKa close to your desired pH. This will give your buffer nearly equivalent amounts of acid and conjugate base so it will be able to neutralize as much H+ and OH- as possible. PURPOSE OF BUFFER:- A buffer solution is used to resist changes in pH when a certain amount of strong acid or base is added to the solution. It is an important part of biological systems in living organisms as well as in the laboratory. The reason a buffer works to maintain a certain pH is that the concentration of weak acid and base is kept in a specific ratio in line with the acid titration curve. The titration curve A titration curve is a graph that relates the relative concentrations of a weak acid to its conjugate base by graphing pH versus amount of base added. In the region of the titration curve where the graph is almost flat, the pH changes very little with added base and therefore this would be a good pH for the buffer. Buffer in cells and blood The main buffer found in living cells is the H2PO4/HPO4- buffer pair. In blood, the main buffer is the H2CO3/HCO3- pair. This system relies on dissociation of carbonic acid, which has a pKa of 6.37. The pH of human blood needs to remain at around a pH of 7.4 and therefore the system also involves carbon dioxide transported to the lungs. Phosphate buffer The phosphate buffer is based on tris (hydroxymethyl) aminomethane or TRIS. This buffer has a pKa of 8.3 and is found both in living organisms as well as used in the laboratory. It is a good buffer because it does not tend to interfere with the system being studied. Buffers in enzymatic reactions Laboratory methods to isolate an enzyme use buffered solutions because an enzyme can only function in a narrow pH range. Enzymes are very sensitive to pH as well as salt concentrations. Therefore, it is important to use a buffer with a very good buffering capacity for the specific pH in order for the experiment to be successful. Physiological consequences Respiration plays a role in buffering of blood by controlling the rate of respiration depending on the need for hydrogen ions or increased acidity. Increasing the rate of respiration is helpful when there is a buildup of hydrogen ions or acidity in the blood. The H+ ions bind to bicarbonate to form carbonic acid. This raises the level of carbon dioxide in the lungs. Increasing the level of respiration removes the excess carbon dioxide. Therefore, here the buffering system is used to keep pH level of the blood within the required narrow range. Features:- The pH of a buffered solution is defined by the Henderson-Hasselbalch equation, which states that the pH of a solution is equal to the acid dissociation constant of the weak acid plus the logarithm of the ratio of the concentrations of conjugate base to the weak acid. The acid dissociation constant is a number that defines the tendency of an acid to dissociate and form hydrogen ions. A strong acid will have a very low dissociation constant, whereas a weaker one may have a significantly higher one, around 5. Considerations:- Buffered solutions have many applications in chemical manufacturing for processes that require a specific pH range to work. This is also true for the human body, which contains many enzymes that are only functional at a specific pH. Outside of this range, the enzymes are either unable to catalyze reactions, or in some case will misfold and become broken down; thus, a mixture of carbonic acid and bicarbonate is used by the body to keep pH of the blood between 7.35 and 7.45.
Sunday, January 19, 2020
In the Heart of the Sea
In the Heart of the Sea The novel â€Å"In the Heart of the Sea: The Tragedy of the Whaleship Essex,†by Nathaniel Philbrick, successfully tells the story of the whale ship Essex that was attacked by a sperm whale 1,500 nautical miles west of the Galapagos, 40 miles south of the equator. Many people know this as the story of â€Å"Moby Dick†, which was based off this event. The novel highlights three themes: man versus nature, survival, and suffering. The novel starts out in the town of Nantucket, an island off the eastern coast of New England.Nantucket, at this time, is known as one of the most successful whaling ports. Docked on the port was the famous Essex, a 20 year whaling boat. The Essex is the pride of Nantucket. It is 87 feet long, 238 tons, equipped with 12 sails and carried several smaller whaling boats that were used when a whale was spotted. After lasting many years, the Essex developed a reputation for being a lucky ship. Many voyages lasted around two to three years in the Pacific Ocean. Many young boys, such as Thomas Nickerson, joined whaling crews at a young age.These crews were mixed of experienced whalers and â€Å"green hands,†men who have never sailed on a whaling ship. Usually, these new crew members would earn around $150 for two years work, so the experienced workers made the most of these â€Å"green hands. †Nantucket was known for its whale products, and was considered the whaling capital of the world. Whale oil was used to fuel lamps and making lamps (because there is no electricity, gas or kerosene). It is also used in margarine, shoe polish and soap. Baleen is a substance that comes from the mouths of the whale.They can be found in many women’s clothing. These two important goods come from whales and the only way to obtain the oil and baleen is to make a voyage out to see and find the whales. At the beginning of the novel, we are introduced to the town of Nantucket and whaling business. His disc ussions of this set us up for the events following later in the book. Philbrick also talks about the relationship between the colonists in Nantucket. They are very close, drawn together by their Quaker religion, similar experiences, and their interests in whaling.In the town, there is a hierarchy within the people. Where a person lived in the town was based on what rank they are in their society. The captain’s home would usually have the best view of the harbor. The seven black crewmen who were brought over to the crew were out casted, and relied on each other. The novel highlights the dangers of being a whaler. Young crewmen, such as Nickerson, were there to gain experience for future journeys. Nantucket was brought together by the whaling industry, and the community would usually see ships off before they took off.The Essex sailed off from Nantucket on August 12, 1819 under the command of 28 year-old Captain George Pollard, Jr. He spent the last four years on the Essex, and knew it very well. However, Philbrick points out that Pollard was not ready for be a captain, and we see why later on in the book. Owen Chase is the captain’s first mate, and Matthew Joy was the second mate. The Essex was operated with a 21-man crew. In chapter 2, Philbrick describes the ship. Also, in this chapter, we get a feel for the isolation of the â€Å"outsiders. The captain and his mates would sleep in cabins that were in the back of the ship, next, the Nantucket colonists would stay in the steerage, and the blacks, separated by the blubber room, stayed in front of the boat. After they embark on their journey, the men begin to complain about their rations. Pollard, was able to talk them into settling for what they had, establishing his power and authority. In chapter 5, on November 20, the crew spots whales 40 miles south of the equator. Chase and his crew go after a whale, which destroys their boat with its tail.When they bring their boat back to the Essex, they s pot a huge sperm whale near the bow of the ship calmly and quietly floating along the surface of the water. The whale began to move quickly towards the ship. The men try to steer Essex away from the whale, but are unsuccessful. The whale rams the ship with its head, and the men are amazed. After the whale revives itself, it struck the ship again, causing the Essex to sink bow-first. The men board their whaleboats after a night of preparation of leaving the Essex. They stripped the sails of the ship and attached them to their boats.The waves splashed over the boat, causing the work to be more difficult. The next morning, the boats take off. Chase and Pollard talk of where to go now that their ship has sunk. They speak about going to the Galapagos Islands, but Pollard noticed the wind direction would not allow them to go there. Next, they speak about the Marquesas, in the west. The men had heard that the inhabitants of the island were cannibals. South of the Marquesas were the Tauamot u Archipelago Islands, but the men had also heard that the islands have a bad reputation.In this conversation, we notice the colonist’s outlook on the unknown. They share a sense of togetherness within each other and no one else. We see this in the attitude of the colonists towards the black crewmen. Pollard decides to sail towards the Society Islands. There, Pollard saw a safer environment with little threat. Chase and Joy argue that the Society Islands would not be a good place to sail towards, and they could sail towards Chile or Peru instead. Pollard conforms to this decision. Here we see that Pollard has become less authoritative after the Essex sinks.In their first three weeks in the boats, the men faced many hardships. They faced thirst and hunger. Their skin had been burnt, salt water burned their sores, and the men, being as weak as they were, were unable to row the boats. On top of all that, another whale attacks Pollard’s boat. The men spot an island in the distance and conclude that they have arrived at Henderson Island. There, they found fresh water and ate crabs and birds. They were able to revive themselves, and this gave them a fighting chance of survival. Three men chose to stay on the island while the others left.Pollard promised he would rescue them after he reached South America. They return back to the ocean, and the men face the same obstacles they faced before they found Henderson Island. The men faced hunger but were still hydrated from the water collected at Henderson Island. Many accepted they weren’t going to live, and gave up their rations. Joy dies in the voyage, and the men bury him at dead. Bad turns to worse when the men realize there is only enough hardtack to last a day or two. On January 20, Lawson Thomas, a black crew member, dies, and the crew contemplates turning to cannibalism.The men concluded that in order to survive, they must eat the dead crew members. It is ironic that the men turned to cannibali sm, because they feared the inhabitants of the Marquesas. Three months after the Essex sank; the remaining two whaleboats are rescued in different areas along the South American coast. Two men were left alive in Pollard’s boat and three men in Chase’s boat. Nickerson, Chase, and Lawrence arrive in Valparaiso, Chile on February 25, 1821, and are taken back to Nantucket aboard whale ship Hero.Both Nantucket and the survivors of the Essex changed after the ship’s sinking. The whaling industry quickly fell to other towns. A fire that burned nearly a third of the town added to the difficulties. The men of the Essex were haunted when recalling what happened. Even Chase was deemed insane. This event caused the town of Nantucket to separate. The townspeople were no longer bonded by whaling, because the industry made a fall. The surviving men of the Essex became hypocritical, turning to cannibalism, one thing they feared and frowned upon. This event helps us understand w hat these men had to do when they are stranded, and teaches us the meaning of nature, survival, and suffering.Bibliography â€Å"Alone in the Pacific. †Salariya Publishing. Web. 18 Oct. 2010. <http://www. salariya. com/web_books/whaling/alone/alone. html>. â€Å"Nantucket Island History. †Nantucket Island Chamber of Commerce. Web. 18 Oct. 2010. <http://www. nantucketchamber. org/visitor/trivia. html>. Philbrick, Nathaniel. In the Heart of the Sea: The Tragedy of the Whaleship. New York,NY: Penguin, 2000. Print. In the Heart of the Sea Nicole Hart HIST 2300- Christopher Trobridge Writing Assignment One October 16, 2010 â€Å"In the Heart of the Sea: The Tragedy of the Whale ship Essex†In order to understand the ramifications of an event such as the sinking of the Essex one needs too understand the community that produces the crew. Nantucket was an island community much more than the literal sense of word. The islanders of Nantucket saw themselves differently than the rest of the word. They learned the skills of whaling from the original Wampanoag tribe. They were Quakers with a stoic sense of standards and community.The whale men from Nantucket saw themselves as superior to most other sailors of that time period. Hardship and perseverance were virtues held by the whale men and the women. The women ran the town while the whale men were at sea for years at a time. This type of work ethic and fortitude, and the worlds desire for oil, combined to make â€Å"the village of Nantucket one of the richest towns in America. †â€Å"In the Heart of the Sea†It also created a close-knit community with a few very successful and influential families that married with each other maintaining a strong central hierarchy.The sinking of the Essex directly affected the community of Nantucket but it was also far reaching to the rest of the country. America was growing as a Nation and its consumption of oil was expanding. The events of the Essex were not only interesting to sailors of the world but also to the mainlanders that consumed the oil. America in the eighteenth century and the early nineteenth century were considered â€Å"†¦a consumer revolution. †â€Å"Of the People†No one knew this fact better than the owners of the whale ships. They understood that whale oil was a commodity to be sold.In order to harvest it at a profit they had to balance their expenses. Every mate on a whale ship received a fraction of the profit that the whale ship would return with the oil it found. The more responsibility a sailor had on a whale ship, the larger his cut. Every expense, food, gear, clothing, water had to be factored in of doing business. For example the captain received the largest share, due to him having the most responsibility, while Thomas Nickerson’s share was the experience he received at a young age on a whale ship plus the room and board that he would receive for two to three years.A situation that occurred early in their journey was a foreboding of things to come. Weeks into there journey the Essex experienced a â€Å"Knockdown†, a knockdown is a severe weather event that led to damage of the Essex. Captain Pollard was slow to respond to the weather issue at hand. The result was damage to half of their whaleboats that they used to harpoon whales. After the damage was done Pollard felt it would be best to return to Nantucket to replenish the ship with a new compliment of whaleboats.First mate Owen Chase convinced the Captain to p roceed on with the whale boats they had with hope of getting more whaleboats of the coast of Africa. This dynamic exposed the type of sailor Captain Pollard was and the type of sailor first mate Chase was. Captain Pollard was proving to be â€Å"a Captain that had the skills of a first mate and first mate Owen was showing to have the skills of a Captain. †â€Å"In the Heart of the Sea. †These two personalities would continue to show themselves later in there journey after the Essex had sunk. When the Essex was rammed and destroyed by the sperm whale, the crews Nantucket heritage served them well.The officers of the Essex were able to maintain order and stifle any panic by the crewmen. They devised a strategy that first mate Chase had championed. Once again Captain Pollard’s initial plan was shelved for fist mate Chase’s plan. The remaining twenty-crew members of the Essex were split into three twenty-five foot whaling boats. Captain Pollard, First mate Chase, and Second officer Hendrix were in charge of the three boats. Even in this situation, a strong sense of the Nantucket community was resident in the division of each boat.The majority of the Nantucketers ended up in Captain Pollards boat. A few of the remaining Nantucketers ended up in First mate Chase’s boat and the majority of African American sailors ended up in second mate Hendrix’s boat. First mate Owen Chase proved to be a relentless advocate for hope. Thomas Nickerson saw another side of First mate Chase when their journey first began by seeing how curt Chase was to the crew. On the island of Nantucket Owen Chase was a gentlemen but at sea Chase took a role of being very demanding and wanting things done correctly.After the sinking of the Essex the crewmembers were struggling with the situation they were in and Chase changed his method of handling of the crew. When Chase saw the crew was losing spirit he showed a more â€Å"maternal†side. This chan ge in attitude was critical in the survival of the crewmembers that made it. The events that led to the cannibalism of crewmembers of the Essex were presented differently to Captain Pollard’s boat and first mate Chase’s boat. Captain Pollards and Hendrix boat became separated from Chases boat.The African American crewmembers having a low body fat content and a mineral deficient diet became prone to death before the Nantucket crewmembers. As the African American crewmembers died the living crewmembers consumed them. When there only living crew members left on Pollards boat they resorted to drawing lots to see who would give up their life as food and who would kill that sailor. On first mate Chase’s boat one of the sailors passes and the elect to consume his body. It appears that cannibalism was a common event that occurred in these situations.To this day human beings get presented with this dilemma, such as the plane crash in the Andes. As for me I would rather c hose death than the consuming of my mates. Spending months at a time with these men I would feel as though I was eating a family member and would rather wait for death than eat a fellow mate. Although I would have the pressure of supporting my family and wanting to return home, eating a human being I believe would be a lot easier said then done. In the grief that Captain Pollard experienced having to eat his nephew then facing his Aunt would be something I don’t think I could endure or ever live with.For Nantucket and the men involved in whale hunting it is more than just a hunt. It was a way of life, a way of survival, and the entire focus of a town. This novel contained more than just the story of the ramming of the Essex, it was more of a story of the hardships faced, the dedication that comes with the job of whaling, and the raw emotions of the men involved. This novel proved the importance of whaling in that time period to not only Nantucket but to the entire Nation, and how it foreshadowed how our economy would be today.Lastly to end with the mission of the Nantucket Quakers â€Å"†¦to maintain a peaceful life on land while raising bloody havoc at sea. †This was their life, their survival and it now is their history. Works Cited James Oakes, Michael Mcgerr, Jan Ellen Lewis, Nick Cullather, Jeanne Boydston. â€Å"Of the People: A history of the United States. †New York: Oxford University Press. Nathaniel Philbrick. â€Å"In the heart of the sea:The tradgedy of the Whaleship Essex†New York: Penguin Books, 2000.
Friday, January 10, 2020
Review what your role, responsibilities and boundaries as a teacher would be in terms of the teaching/training cycle Essay
There is often an assumption that, if we give people some training it’s bound to do some good and often simply experiencing a training event can result in learning. However the chances are far greater when a systematic approach to teaching is applied. The ‘teaching/training cycle’ is the classic method of carrying out the teaching process. It is a logical and structured approach to teaching which ensures that the needs of the learner are effectively met. The teaching cycle is a cyclical model of experiential learning which consists of a five stage learning sequence which encourages continuity from one experience to another. It can be approached at any stage, but it needs to be followed through to be effective. Taking shortcuts at any stage can lead to ineffective teaching/training. It is paramount that the role, responsibilities and boundaries as a teacher are understood and integrated within the parameters of the cycle for learning to be effective. A teacher’s role in the Lifelong Learning Sector is broad; indeed Harden and Crosby (2000:334) identified twelve distinct roles of the teacher, however this falls short of the nineteen roles identified by Wilson (2008:6). Some of the functions sit within specific stages whilst others embrace the whole of the training cycle. Identifying learners’ specific needs is critical because if these are not identified, the training will not achieve the intended outcome. It is vital to ensure that the training has the correct purpose. At this stage it is important to assume nothing. Stage One- A diagnostic assessment (Training Needs Analysis) evaluates what is already known whilst exploring learning outcomes. This is accompanied by initial assessment (S4L screening); an analysis of Learning Styles and ICLP (learning plan). At this first stage it is key to establish boundaries with the learner; Bluestein (2010 Online) identifies eleven reasons to use boundaries including â€Å"being able to express your limits and to communicate the conditions or availability†. The teacher must foster integrity and confidentiality in order to establish trust and respect with the learner. It is also important to remember the teacher’s role as a role model and that you only get one opportunity to create a good first impression. As a teacher it is imperative that you are punctual; dress appropriately; use appropriate language and feedback at the appropriate times. It is important to portray a professional image and to be seen to work within the boundaries of the law, professional codes, values and ethics. Teachers are responsible for pastoral care; for looking after the personal and social wellbeing of the individual including the health and emotional support of the learner. Often issues can be picked up early in the cycle and the teacher can then support the individual. The learner may need financial, health and learning support which can be gained via referral to a support service. Occasionally they may need a break from the programme in order to resolve personal issues and only then is the individual able to reach their full potential. The needs and objectives of the learner should be routinely examined throughout the programme through direct and indirect feedback so that the individual feels supported and valued and is able to reach their full potential. Stage Two – The teacher is responsible for planning and designing a programme of study that responds to these needs. This involves the teacher designing a scheme of work and model of delivery; individual lesson plans and sourcing resources. Stage Three – Stage three focuses on delivery with the teacher providing appropriate methods, resources and support while facilitating learning. Approaches to learning will depend on the number of students and learning styles of the group. Stage Four – Giving learners access to fair assessment; the teacher assesses and checks learning and monitors progress. This is an opportunity to feedback on success or initiate change. Stage Five – Involves gaining feedback as part of the evaluation process; the teacher and the learner review the effectiveness of the course and consider any information, advice and guidance (IAG) the learner may need to progress with their development. The teacher analyses retention and success levels. The teacher is responsible for contributing towards the administration of the programme and contributing to Quality Assurance. The teacher has a duty of care to facilitate learning to everyone without discrimination within a safe learning environment and to ensure that all learners receive a positive learning experience and achieve their goals. References Bluestein, J. ( © 2010), 11 Reasons to use Boundaries. http://www.janebluestein.com/handouts/bound_reasons.htmlDeerfield each, FL: Health Communications, Inc., Harden et al (2000) Medical Teacher. Volume 22, Issue 4 July 2000, pages 334-347. London: Informa Plc. Wilson, L. (2008) Practical Teaching: A Guide to PTLLS & CTLLS. London: Cengage Learning Bibliography Bluestein, J. ( © 2010), 11 Reasons to use Boundaries. http://www.janebluestein.com/handouts/bound_reasons.htmlDeerfield each, FL: Health Communications, Inc., Fox, R. (2005) Teaching and Learning. Oxford: Blackwell Publishing Ltd. Harden et al(2000) Medical Teacher. Volume 22, Issue 4 July 2000, pages 334-347. London: Informa Plc. Petty, G. (2006) Evidenced Based Teaching. Cheltenham: Nelson Thornes Ltd. Wilson, J. (2000) Key Issues in Education and Teaching. London, New York: Cassell Wilson, L. (2008) Practical Teaching: A Guide to PTLLS & CTLLS. London: Cengage Learning
Thursday, January 2, 2020
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