The Discarded Phlogiston Theory in Early Chemistry

The Discarded Phlogiston Theory in Early Chemistry Mankind may have learned how to make fire many thousands of years ago, but we didnt understand how it worked until much more recently. Many theories were proposed to try to explain why some materials burned, while others didnt, why fire gave off heat and light, and why burned material wasnt the same as the starting substance. Phlogiston theory was an early chemical theory to explain the process of oxidation, which is the reaction that occurs during combustion and rusting. The word phlogiston is an Ancient Greek term for burning up, which in turn derives from the Greek phlox, which means flame. Phlogiston theory was first proposed by the alchemist Johann Joachim (J.J.) Becher in 1667. The theory was stated more formally by Georg Ernst Stahl in 1773. Importance of Phlogiston Theory Although the theory has since been discarded, its important because it shows the transition between alchemists believing in the traditional elements of earth, air, fire, and water, and true chemists, who conducted experimentation that led to the identification of true chemical elements and their reactions. How Phlogiston Was Supposed to Work Basically, the way the theory worked was that all combustible matter contained a substance called phlogiston. When this matter was burned, the phlogiston was released.  Phlogiston had no odor, taste, color or mass. After the phlogiston was freed, the remaining matter was considered to be deflogistated, which made sense to the alchemists, because you couldnt burn them any more. The ash and residue left over from combustion was called the calx of the substance. The calx provided a clue to the error of phlogiston theory, because it weighed less than the original matter. If there was a substance called phlogiston, where had it gone? One explanation was the phlogiston might have negative mass. Louis-Bernard Guyton de Morveau proposed it was simply that phlogiston was lighter than air. Yet, according to Archimedes principle, even being lighter than air couldnt account for the mass change. In the 18th century, chemists did not believe there was an element called phlogiston. Joseph Priestly believed flammability might be related to hydrogen. While phlogiston theory didnt offer all the answers, it remained the principle theory of combustion until the 1780s, when Antoine-Laurent Lavoisier demonstrated mass was not truly lost during combustion. Lavoisier linked oxidation to oxygen, conducting numerous experiments which showed the element was always present. In the face of overwhelming empirical data, phlogiston theory was eventually replaced with true chemistry. By 1800, most scientists accepted oxygens role in combustion. Phlogisticated Air, Oxygen, and Nitrogen Today, we know that oxygen supports oxidation, which is why air helps to feed a fire. If you try to light a fire in a space lacking oxygen, youll have a rough time. The alchemists and early chemists noticed that fire burned in air, yet not in certain other gases. In a sealed contained, eventually a flame would burn out. However, their explanation wasnt quite right. The proposed phlogisticated air was a gas in phlogiston theory that was saturated with phlogiston. Because it was already saturated, phlogisticated air did not allow the release of phlogiston during combustion. What gas were they using that didnt support fire?  Phlogisticated air was later identified as the element nitrogen, which is the primary element in air, and no, it wont support oxidation.

colon cancer essays

colon cancer essays So many factors are thought to come into play in determining who gets colorectal cancer and who doesnt that its hard to choose one as the most important. A diet that is low in fat and red meat and high in calcium and folate may contribute to preventing colorectal cancer, and although the verdict is not yet in on the benefits of fiber, a diet rich in fruits and vegetables with a high fiber content would be beneficial in many ways. Daily doses of non-steroidal anti-infla mmatory agents (NSAIDs), such as aspirin and naproxen, may lower your risk of colorectal cancer by as much as 40 percent. "But we dont recommend these medications for patients who dont need them for other reasons," says AGA member Francis Giardiello, MD, Professor of Medicine and Director, Division of Gastroenterology, at the Johns Hopkins School of Medicine. His recommendation, then, for the best way to fight off colorectal cancer? Get to know your family better. "Family history is very important," says Dr. Giardiello. "People with first-degree relatives (parents, siblings or children) who contracted colon cancer before age 50 have a 22 percent greater chance of contracting it themselves." He adds that people with a family history of polyps, benign growths that often are precursors of cancer, also have an increased risk. Approximately 15 to 50 percent of colorectal cancers are familial, meaning they tend to occur in more members of a family than expected by chance alone. Two hereditary causes of colorectal cancer are familial adenomatous polyposis (FAP) (characterized by hundreds or even thousands of polyps developing in the colon or rectum at a young age) and hereditary nonpolyposis colorectal cancer (HNPCC) (an inherited tendency to develop colorectal cancer at a younger age). If you discover that you are at high risk for colorectal cancer or polyps, theres no need to despair - the enemy you know is better than the one you don ...

Argue against texting and driving Essay Example | Topics and Well Written Essays - 250 words

Argue against texting and driving - Essay Example According to research, texting while driving is considered as being more dangerous than drunk driving. This is especially due to the fact that this activity diverts the attention of a driver at a minimum period of 5 seconds, which is equivalent to a blind person driving for a distance of approximately 100 meters (Kiesbye 41). According to 2008 statistics, distracted driving caused the death of more than 5000 people and more than 500000 injuries in the US alone (Regan 39). Clearly, this is a significant loss, which could have been avoided were there a national ban on some of the distractions such as texting while driving. Drivers should be aware of the fact that life is precious, therefore, should be protected by all means as it cannot be compared to a text message no matter how urgent it might be. They are in control of their vehicles and as such, they have the liberty and the right to stop at convenient places to text after which they can continue driving. Indeed, a disciplined driver should always switch off his mobile phone, while driving, especially if the phone is not connected to a Bluetooth headset. Most of the phones in the market have the capability to record voicemails and also to hold incoming messages until the user switches on his handset, therefore, there is no justified reason as to why a person should end up in hospital or dead as a result of accidents caused by careless utilization of mobile