Chemistry Open Book Paper Essays - Spectroscopy,

Chemistry Open Book Paper Atomic spectroscopy is a chemical analysis technique and it is used to identify what elements are in a compound. It uses the idea of a photon being absorbed or emitted whenever an electron changes from one energy level to another. The diagram below shows sodium salt being sprinkled onto a flame and yellow light being emitted. Emission spectra are produced by thin gases in which the atoms do not experience many collisions (because of the low density). The emission of yellow light occurs because the electrons of the sodium salt have been promoted to a higher electronic energy state but have then fallen back down and emitted the energy as an electromagnetic wave, in the wavelength corresponding to yellow which is ? 600 nm. The more intense that the yellow band is the more abundant the sodium salt present. The diagram (left) shows an atomic excitation caused by the absorption of a photon and an atomic de-excitation caused by emission of a photon. In each case the wavelength of the emitted or absorbed light is exactly such that the photon carries the energy difference between the two orbits. This energy may be calculated by multiplying the Plank constant by the wavelength of the light. Thus, an atom can absorb or emit only certain discrete wavelengths (or equivalently, frequencies or energies). This diagram shows white light being shone through sodium vapour and the resulting spectra on a board. An absorption spectrum occurs when light passes through a cold, dilute gas and atoms in the gas absorb at characteristic frequencies; since the re-emitted light is unlikely to be emitted in the same direction as the absorbed photon, this gives rise to dark lines (absence of light) in the spectrum. Absorption spectroscopy can only be carried on a substance in solution or gaseous form. The presence of the dark band shows that the sodium vapour had absorbed the light in the yellow region. Sodium salt has absorbed energy but it is not re-emitted or just not re-emitted efficiently and so the wavelength of the light increases, leaving the observed dark band where yellow was expected. The Sun appears yellow because that is the main wavelength the sun emits radiation at. This is shown in a graphically below. For each hot object there is a corresponding colours. Those stars with colours of lower wavelengths are lower in temperatures. For example something that appears red has a temperature of ? 3000 K. But something blue has a temperature of ? 10000 K. So finding the predominant colour of the sun then its temperature could be determined. The Suns spectrum resembles that of something around 5000 K. By studying the emission spectra captured on the photographic film for dark bands , the composition can be found. Because interstellar clouds have a temperature of between 10-50 K, radiation emitted has much shorter wavelengths, so different techniques to the ones above have to be used. The wavelengths are in fact in the order of 0.001 m so the can be picked up by radio telescopes on earth. Here is a picture of one below. A neutral hydrogen atom (H I) consists of 1 proton and 1 electron. The proton and electron spin like tops with their spin axes either parallel or anti-parallel. When hydrogen atoms switch from the parallel to the anti-parallel configuration they emit radio waves with a wavelength of 21 centimetres and a corresponding frequency of exactly 1420 MHz. This is called the 21-centimetre line. Thus, radio telescopes tuned to this frequency can be used to map the great clouds of neutral hydrogen found in interstellar space. Radio telescopes identify which elements are present and how abundant they are and then the conditions are replicated here on earth. But this requires keeping the elements in gaseous form at low temperatures (as low as 7 K) without condensing. This requires using CRESU apparatus .It takes advantage of the flow properties of gaseous expansions from convergent-divergent Laval nozzles into low-pressure environments, producing a flow of gas, which is uniform in temperature, density and velocity, and carries on for hundreds of millimetres and hundreds of microseconds after leaving the nozzle exit. Frequent collisions occur during the controlled expansion within the nozzle .The expansion is slow enough to maintain thermal equilibrium, but rapid enough that condensation is avoided. A uniform,

5 Ways To Avoid Interview Panic

5 Ways To Avoid Interview Panic So much work goes into the job search process that by the interview phase, emotions can run tense. You’ve worked so hard to get in the door and now the stakes are high, your palms are sweating, and you’re a bundle of nerves. Here are five things you can do to keep your cool and rock your interview.1. Prepare before you goThe best way to not panic in the interview is to be super well-prepared. If you know everything there is to know about the company and the position, if you have answers to all the usual questions, plus a few unusual ones, if you’re ready with thoughtful, constructive questions for your interviewer when prompted†¦ if you’ve done all of this, then you won’t be nervous about what’s to come. You’ll look confident, driven, and smart, and they’ll know without a doubt you wanted the job enough to do your homework. Who knows, the interview could even turn out to be enjoyable for both of you.2. Get some sleepYouâ₠¬â„¢re nervous. You can’t imagine calming down enough to go to sleep before the big day. But rather than staying up all night pacing (or watching Netflix, or surfing Facebook on your phone) in your darkened bedroom, make yourself a cup of tea and go to bed. You’ll be much fresher and sharper tomorrow, and infinitely less stressed.3. Practice makes perfectGet everything ready the night before. Try on and lay out what you plan to wear. Make sure your shoes are polished and your documents are in order. Then see if you can’t get a friend or roommate to practice asking you questions and assessing your answers. Saying things out loud the night before can make you sound more put together when you’re in the interview.4. Pump upListen to music that either soothes you or motivates you on your way to the interview. Studies show it can have a measurable effect. At very least, it’ll put a bit of bounce into your step and allow you to walk in relaxed and confide nt.5. Show up earlyBeing late is a big strike against you. But being a little early never hurt- especially if you’ve never been to that particular part of town or office before. You’ll be glad you have a few minutes of leeway in case your GPS messes up or you run into unexpected traffic.

Sleeping Beauty Assignment Example | Topics and Well Written Essays - 250 words - 2

Sleeping Beauty - Assignment Example The principal themes in the story sleeping beauty gender empowerment, gender equity, capitalism, equitable sharing of resources, non- discrimination, democracy, corruption and fairness equity in resource allocation. Disney movies have incorporated dancing so is the story of sleeping beauty, Disney movies also has a lot of animation using animals as human characters. Sleeping beauty also is an animation type of genre. The politics of gender in the sleeping beauty champions that gender equity is critical in today’s life. Discrimination on gender is something old fashioned. Equitable participation as depicted in the many women actors in the sleeping beauty story. Women empowerment is a clinical step towards solving domestic challenges. In the story, women can be referred to as the mothers of nature since the play the nurturing role effectively. Increased participation of w indicates the will to grab equal opportunities that come their way in the daily life of the society. In the western culture gender discrimination is