Crystals Essays - Crystallography, Phase Transitions,

Crystals Crystals What is a crystal? A crystal is a solid substance with definite geometric shapes and molecules that are arranged in a repeating pattern (Compton?s ). Crystals have fixed angles between its faces, which have distinct edges. If the faces of a crystal can reflect light, then it will sparkle (Stangle). Crystals have constant angles because of the regular arrangement of its particles. There are seven types of crystals: cubic, tetragonal, orthorhombic, hexagonal, trigonal, monoclinic, and triclinic (Dr. Boyle). Crystals are classified by the shapes of their lattice or the ?regular, periodic configuration of particles? (American Heritage). There are two different types of lattices. There are primitive lattices where there is only one lattice point per unit cell. There are also non-primitive lattices. They are the ones with more than one lattice point per unit cell. Crystals can also be classified by their physical/chemical properties. There are four types of crystals classified this way. They are covalent, metallic, ionic, and molecular (Dr. Boyle). A covalent crystal is a crystal which is one big molecule. They usually have extremely high melting points. An example of a covalent crystal is a diamond and zinc sulfide (Dr.Boyle). Metallic crystals have high melting points and densities. They are metal atoms which sit on lattice sites while the outer electrons from these atoms flow freely around the lattice (Dr. Boyle). Ionic crystals are crystals where the individual atoms do not have covalent bonds among themselves. These atoms are held together by electrostatic forces. They are also very hard and have a relatively high melting point. Sodium chloride (NaCl, salt) is an example of an ionic crystal (Dr. Boyle). Molecular crystals are crystals where there are ?recognizable molecules in the structure and the crystal is held together by non-covalnet interactions? such as hydrogen bonding (Dr. Boyle). Sugar is an example of a molecular crystal. These crystals tend to have low melting points and are soft (Dr. Boyle). Crystals start growing by a process called nucleation. They are produced in solutions. The temperature and pH balance of the solutions must be controlled well. Crystals start growing one of two ways: unassisted nucleation, crystals that start with the molecules themselves or assisted nucleation, with the help of some solid matter already in the solution (Dr. Boyle). In unassisted nucleation, molecules of the solute are in the solution. Most of the time the solute molecules only see the solvent molecules around them. Sometimes the solute molecules can see other solute molecules and they become attracted to one another if the compound is solid and pure (Dr. Boyle). These molecules will stay together for a little while and will eventually be separated by other internal forces. However, sometimes the molecules will stay together long enough to meet up with a third, then a fourth, and then even a fifth solute molecule. When this happens the combined attraction force eventually becomes stronger than the other forces within the solution (Dr. Boyle). This attraction force tends to disrupt the formation of these aggregates. When this happens a protocrystal or a pre-crystal becomes a nucleation site (Dr. Boyle). As the protocrystal floats around in the solution, it encounters other solute molecules. These other molecules feel the attractive force of the protocrystal and decide to join the group of molecules (Dr. Boyle). This is when the crystal begins to grow. Crystals grow form the outside instead of the inside. The crystal molecule grows until it can no longer remain ?dissolved? in the solution and falls out of the solution (Dr. Boyle). After this happens, the other solute molecules grow on the surface of the crystal. The crystal gets bigger until there is an equilibrium, or ?a state of a chemical reaction in which a forward and reverse reaction occur at equal rates so that the concentration of the reactant and product do not change with time? (American Heritage). When there is equilibrium between the solute molecules in the crystal and the solute molecules in the solvent the crystal no longer get bigger (Dr. Boyle). In assisted nucleation the same process is followed as in unassisted nucleation. The only difference is that a solid surface such as a stone or brick acts as a meeting for all of the solute

Free Essays on Abolish Affirmative Action

Are we not all equal? Are we not all able to get an education? Then why is affirmative action needed? If we are equal and have the same skills why should a minority, certain race, religion or sect get a job over the average â€Å"Joe†? This is why I believe affirmative action should be abolished. Affirmative action is a policy or a program that seeks to redress past discrimination through active measures to ensure equal opportunity, as in education and employment. It is called preferential selection, which means selection on the basis of race, gender, or ethnicity. It was introduced by president Lyndon B. Johnson’s Executive Order 11246, requiring employers to use â€Å"affirmative action† to make sure they were not discriminating. In doing this it may be forcing businesses to hire less qualified personel. People may also cheat this system by taking advantage of a businesses obligation to affirmative action. People may fake indian heritage, hispanic, or african decent. An example of this is the University of Colorado which hired Ward Churchill. He became an associate member of the Keetoowah tribe by telling them he was an author who could help their people. To become a member of this Cherokee tribe it is required to have at least one-fourth Cherokee blood, but Churchill is believed to have less than one-sixteenth, which doesn’t qualify him as American Indian. The university had hired him, without any real qualifications, to fulfill their requirements. Now he is being charged with plagiarizing is work, threatening students and comparing victims of September 11, 2001 to the Nazi party. Over the past few years, affirmative action has been under attack by those who claim that it is nothing more than â€Å"reverse discrimination†. Given the situation where two candidates for college admissions or for a job or promotion possessed about equal qualifications, voters were asked whether or not any weight should be given to th... Free Essays on Abolish Affirmative Action Free Essays on Abolish Affirmative Action Are we not all equal? Are we not all able to get an education? Then why is affirmative action needed? If we are equal and have the same skills why should a minority, certain race, religion or sect get a job over the average â€Å"Joe†? This is why I believe affirmative action should be abolished. Affirmative action is a policy or a program that seeks to redress past discrimination through active measures to ensure equal opportunity, as in education and employment. It is called preferential selection, which means selection on the basis of race, gender, or ethnicity. It was introduced by president Lyndon B. Johnson’s Executive Order 11246, requiring employers to use â€Å"affirmative action† to make sure they were not discriminating. In doing this it may be forcing businesses to hire less qualified personel. People may also cheat this system by taking advantage of a businesses obligation to affirmative action. People may fake indian heritage, hispanic, or african decent. An example of this is the University of Colorado which hired Ward Churchill. He became an associate member of the Keetoowah tribe by telling them he was an author who could help their people. To become a member of this Cherokee tribe it is required to have at least one-fourth Cherokee blood, but Churchill is believed to have less than one-sixteenth, which doesn’t qualify him as American Indian. The university had hired him, without any real qualifications, to fulfill their requirements. Now he is being charged with plagiarizing is work, threatening students and comparing victims of September 11, 2001 to the Nazi party. Over the past few years, affirmative action has been under attack by those who claim that it is nothing more than â€Å"reverse discrimination†. Given the situation where two candidates for college admissions or for a job or promotion possessed about equal qualifications, voters were asked whether or not any weight should be given to th...

Module 8 Essay Example | Topics and Well Written Essays - 1250 words

Module 8 - Essay Example It is also common for temple walls to be adorned with sculptures of scroll-like foliage, images of women, and couples exhibiting romantic scenes. These human figures are voluptuous, curved, and appear to be in perpetual motion, representing growth, prosperity, and abundance, and were regarded as auspicious motifs (India Netzone,2009). A famous example of a temple with ornate scenes from the Ramayana and the Mahabharata is the Virupaksha temple, the biggest temple located in Pattadakal which is a World Heritage Site. Another, the Hutchimali Temple, displays a sculpture of Vishnu sitting on top of a large cobra. A third, the Ravalphadi cave temple, is a celebration of the many forms of Shiva. These temples depict the gods in human forms or derivations thereof – e.g., Vishnu is sometimes shown as a male form with four arms representing his wide-reaching power. The human form is therefore deified in Hindu architecture. References: Acharya, Prasanna Kumar (1946). An Encyclopaedia o f Hindu Architecture. Oxford University Press. India Netzone (2009) ‘Hindu Art’. IndiaNetzone. 10 Aug 2009. Retrieved 9 October 2012 from http://www.indianetzone.com/42/hindu_art.htm Rajan, K.V. Soundara (1998). Rock-Cut Temple Styles. Somaiya Publications: Mumbai. ISBN 81-7039-218-7 http://www.google.com.ph/imgres?um=1&hl=en&client=firefox-a&sa=N&rls=org.mozilla:en-US:official&biw=1036&bih=602&tbm=isch&tbnid=7XMgE3Kxs5sNSM:&imgrefurl=http://www.viasingapore.com/author/admin/&docid=6C8I_lf8GUOvbM&imgurl=http://www.viasingapore.com/wp-content/uploads/2012/09/vacation_645x320-1.jpg&w=645&h=320&ei=gyF5UPHFK8HPrQetoYHYCw&zoom=1&iact=hc&vpx=114&vpy=331&dur=1799&hovh=158&hovw=319&tx=127&ty=136&sig=113358727395579824739&page=1&tbnh=133&tbnw=266&start=0&ndsp=16&ved=1t:429,r:11,s:0,i:100 Category B (3) Discuss the contemporary art of Meera Mukherjee's Ashoka at Kalinga. How does her art embody the past with the present? Meera Mukherjee is a modern Indian sculptor whose artistic efforts were directed at incorporating local, traditional, and non-western themes and techniques, with those of the international, modern, and western approaches. Her masterpiece, Ashoka at Kalinga, exhibits both the influences of her German training and her stay with the Bastar tribe in central India, where she studied their unique method of casting bronze. Ashoka was a great emperor who ruled during the 3rd century B.C., specifically the last major emperor of the Mauryan dynasty. The conquest of Kalinga, a country on the east coast; the battle was Ashoka’s only aggressive war. It lasted a full year and turned out triumphant but bloody, during which 100,000 people were slain, 150,000 were taken into captivity, and an untold number died of starvation. Severely distressed by the violence of war, Ashoka thereafter rejected war and adopted Buddhism as his empire’s official religion. Drawing upon this significant segment of India’s history, Mukherjee used Ashoka at Kalinga as a means of peaceful protest against the political violence in late 20th century India. By depicting a moment in her country’s past through her sculpture, she was able to make a connection with the present events with the same timeless message – the rejection of violence. Aside from the theme, Mukherjee