...A thermal expansion valve (often abbreviated as TEV, TXV or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of refrigerant flow into the evaporator thereby controlling the superheating at the outlet of the evaporator. Thermal expansion valves are often referred to generically as "metering devices". Flow control, or metering, of the refrigerant is accomplished by use of a temperature sensing bulb filled with a similar gas as in the system that causes the valve to open against the spring pressure in the valve body as the temperature on the bulb increases. As the suction line temperature decreases, so does the pressure in the bulb and therefore on the spring causing the valve to close. An air conditioning system with a TX valve is often more efficient than other designs that do not use one. A thermal expansion valve is a key element to a refrigeration cycle; the cycle that makes air conditioning, or air cooling, possible. A basic refrigeration cycle consists of four major elements, a compressor, a condenser, a metering device and an evaporator. As a refrigerant passes through a circuit containing these four elements, air conditioning occurs. The cycle starts when refrigerant enters the compressor in a low pressure gas form. The refrigerant is compressed by the compressor to a high pressure gas state. The high pressure gas then enters the condenser. The condenser precipitates the high pressure gas to a high pressure liquid...
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...acid-base properties of amphiprotic substances. Information Acid – • a compound that yields hydronium ions, H3O+(aq), as positive ions in aqueous solution (Arrhenius definition). • a compound that donates a hydrogen ion (H+) to another species (BronstedLowry definition). Base – • a compound that yields hydroxide ions, OH-(aq), as negative ions in aqueous solution (Arrhenius definition). • a compound that accepts a hydrogen ion, (H+), from another species (Bronsted-Lowry definition). Neutral solution – • contains hydrogen ions and hydroxide ions in equal concentrations. Note: In the context of acid-base chemistry, the hydrogen ion usually is referred to as a proton because an atom of hydrogen contains one proton and one electron when it loses the electron during ion formation all that is left is the nucleus, which is one proton. © POGIL – 2005 Authored by Josephine Parlagreco and Robert Dayton Edited by Linda Padwa and David Hanson, Stony Brook University 1/4 Introduction to Acids and Bases Model 1. NaOH(s) + H2O(l) → Na+(aq) +...
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...can’t be broken into smaller pieces * In any one element, all atoms are exactly alike * Atoms of different elements are different * Atoms of 2 or more elements can combine to form compounds * Atoms of each element have a unique mass * The masses of the elements in a compound are always in constant ratio Bohr Theory: Danish physicist NEILS BOHR * Electrons are arranged in definite shells or NRG levels, considerable distance from the nucleus * Electron configuration: how electrons are arranged * # of electrons = the atomic # of atoms Sir James Chadwick: 1932 * Discovered in the nucleus another particle, neutron * Neutron has same weight as the proton * Neutron has no electrical charge * Nucleus is made up of protons and neutrons * # of protons is = to # of electrons, which is the atomic # of atom Atoms & Molecules * Atoms combine & arrange to form different compounds & molecules * Molecule: 2 or more atoms that are joined together chemically to act as a single unit * Chemical Bond: is the force that holds atoms together * Compound: 2 or more different atoms joined together chemically * All compounds are molecules, but not all molecules are compounds Ex: Oxygen gas = O2 is a molecule, not a compound (both atoms are alike) Water= H20 is a molecule & a compound (2 diff elements joined 2gether) * Molecules can contain as many as a billion atoms or as few as two atoms Kinetic...
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... * The principle behind NMR is that many nuclei have spin and all nuclei are electrically charged. If an external magnetic field is applied, an energy transfer is possible between the base energy to a higher energy level (generally a single energy gap). The energy transfer takes place at a wavelength that corresponds to radio frequencies and when the spin returns to its base level, energy is emitted at the same frequency. The signal that matches this transfer is measured in many ways and processed in order to yield an NMR spectrum for the nucleus concerned. Chemical Shift describes the fact that all nuclei containing an odd number of protons and neutrons have something called a “spin” –a built-in type of movement which is also called resonance. This movement is slightly different for different protons in a given molecule, and can change depending on the chemical environment. The Zeeman Effect explains what happens when a spectral line—an emission or absorption point in an otherwise uniform spectrum—is split into components while in the presence of a magnetic field. In NMR spectroscopy, magnetic nuclei are aligned with a constant magnetic field. This alignment is then disturbed by applying an alternating magnetic field to the nuclei. Both...
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...showed that there were gaps in the atomic number sequence at numbers 43, 61, 72, and 75. These spaces are now known, respectively, to be the places of the radioactive synthetic elements technetium and promethium. Moseley predicted the two more undiscovered elements, those with the atomic numbers 72 and 75, and gave very strong evidence that there were no other gaps in the Periodic Table between the elements aliminium (atomic number 13) and gold (atomic number 79). Moseley's law provided a reasonably complete experimental set of data supporting the (at that time new from 1911) Ernest Rutherford/Antonius Van den Broek concept of the atom, in which atomic number is understood as representing physically exactly the number of positive charges (protons) in a central atomic...
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...The periodic table can give the majority of information on any elements. Based on the reading all matter is composed of elements, which are substances that cannot be broken down into other substances. Looking at Nitrogen, we can see that the atomic number is seven (number of protons in the nucleus), the symbol is N, and the atomic weight of Nitrogen is 14.01. Nitrogen is one of four elements that make up living cells. A Nitrogen atom has protons and neutron in the central nucleus with two electrons on the inside and four electrons on the outside. Electrons on the outer shell will interact electrons of atoms to determine the chemical properties of atoms. Nitrogen-15 isotopes neutrons vary unlike the Nitrogen atom. The fifteen stands for the atomic weight, seven protons and eight neutrons. The Nitrogen Ion has varying numbers of electron. An Ion charge is determined by its name, with an extra negative charge for each extra electron or positive...
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...1. What are the components of an atom? In order to get a thorough understanding of the physical properties of radiation and how x-rays are produced, a dental radiographer has to know the structure, characteristics, and interactions of atoms. Atoms are the basic particles that compose matter, matter is anything that occupies space and has mass. All atoms consist of the same subatomic particles: protons, electrons, and neutrons. The center of atom is called the nucleus, and it consists of neutrons and protons. Neutrons have no electrical charge, but their mass is about the same as of protons. Protons have a positive charge. The nucleus contains over 99.9% of the mass of the atom, but occupies little volume. The third particle type is electron. It has a negative charge and a tiny mass, and can be found in the orbitals, a probability distribution maps showing where the electrons are likely to be found. Electrons remain in the orbits due to the nature of electrostatic force, or attraction between the positive nucleus and the negative electron. 2. What is ionization? How does it occur?...
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...Chapter 2: Chemistry and molecules of life -Homeostasis- The maintenance of an internal environment -Energy- The ability to do work -Metabolism- Chemical reactions in a cell that allows it to use energy -Element- A chemically pure substance that cannot not be broken down -Matter- anything that takes of space -Atom- smallest unit of an element -Proton- positively charged particle inside nucleus -Electron- negatively charged particle around nucleus -Neutron- uncharged particle inside nucleus -Nucleus- core of an atom -Covalent Bond- strong bond from the sharing of electrons between two atoms -Molecule- atoms together by covalent bond -Organic Molecule- carbon based molecule with at least one C-H bond -Inorganic Molecule- lacks carbon and C-H bond -Carbohydrate- organic molecule made up of sugars -Protein- organic molecule made up of amino acid -Lipids- organic molecule that repels water -Nucleic Acids- organic molecule made of nucleotides DNA/RNA -Macromolecules- organic molecules made up of living organisms (carbohydrates,protiens,nucleic acids) -Monomer- one chemical subunit -Polymer- molecule made up of individual subunits -Monosaccharide- monomer of a carbohydrate -Amino Acid- monomer of a protein -Nucleotide- monomer of a nucleic acid -Cell- basic structure of living organisms -Phospholipid- lipid that forms a cell membrane -Phospholipid Bilayer- double layer lipid that characterizes biological...
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...frequency of 2.4 GHz. a) What is the magnetic field strength? b) The electrons’ motion takes place inside a special tube called a magnetron. If the magnetron can accommodate electron orbits with a maximum diameter of 2.5 mm, what is the maximum electron energy? Problem 3. An electron moves in a circular path perpendicular to a constant magnetic field of magnitude 1.00 mT. If the angular momentum of the electron about the center of the circle is 4.00(10-25 J(s, determine a) the radius of the path, and b) the speed of the electron. Problem 4. A cyclotron designed to accelerate protons has a magnetic field of magnitude 0.45 T over a region of radius 1.2 m. What are a) the cyclotron frequency, and b) the maximum speed acquired by the protons? Problem 5. A cyclotron is designed to accelerate deuterium nuclei. (Deuterium has one proton and one neutron in its nucleus.) a) If the cyclotron uses a 2.0 T magnetic field, at what frequency should the dee voltage be alternated? b) If the vacuum chamber has a diameter of 0.90 m, what is the maximum kinetic energy of the deuterons? c) If the magnitude of the potential difference between the dees is 1500 V, how many orbits do the deuterons complete before achieving the energy of part (b)? Here's a picture of the cyclotron. You can also refer to the Encyclopedia Britannica reference in the reading assignment for Feb. 18....
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...Homework: Chapter 12 1. How is mass a form of energy? When mass is converted into energy, the amount of energy produced is enormous – equal to the mass of the object multiplied by the speed of light: Energy = mass x (speed of light)2 E = mc2 Einstein’s equation tells us that a given amount of mass cab be converted into a specific amount of energy in any form and vice versa. 2. What are the potential benefits and risks in using nuclear tracers in medical diagnosis? 3. What type of nuclear reaction powers our Sun? The type of nuclear reaction that powers the sun is nuclear fusion (hydrogen nucleus and proton). 4. What form of indoor air pollution is the result of naturally occurring radioactive decay? Radon is a form of indoor air pollution resulting from naturally occurring radioactive decay. 5. Why must uranium be enriched in order to be used in a nuclear power plant? What is changed in the process of enrichment? Nuclear plants has nuclear reactors and so only enriched uranium can be used, so before uranium can be used as fuel for a nuclear reactor, it must first go through a number of processes known as “enrichment.” The enriched uranium oxide must be fabricated into nuclear reactor fuel. These are formed from pressed uranium oxide, which is baked at a high temperature. The pellets are then encased in metal tubes to form fuel rods, which are arranged into a fuel assembly ready for introduction into a reactor. 6. What is the strong...
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...be a result of the Pauli exclusion principle. Two particular examples where the exclusion principle clearly relates matter to the occupation of space are white dwarf stars and neutron stars, discussed further below. Atoms and molecules definition A definition of "matter" that is based upon its physical and chemical structure is: matter is made up of atoms and molecules. As an example, deoxyribonucleic acid molecules (DNA) are matter under this definition because they are made of atoms. This definition can be extended to include charged atoms and molecules, so as to include plasmas (gases of ions) and electrolytes (ionic solutions), which are not obviously included in the atoms and molecules definition. Alternatively, one can adopt the protons Baryonic...
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...accurate list of the atomic mass of the elements became available at a conference in Karlsruhe, Germany in 1860 that real progress was made towards the discovery of the modern periodic table. This area of the website celebrates the work of many famous scientists whose quest to learn more about the world we live in and the atoms that make up the things around us led to the periodic table as we know it today. Chemists have always looked for ways of arranging the elements to reflect the similarities between their properties. The modern periodic table lists the elements in order of increasing atomic number (the number of protons in the nucleus of an atom). Historically, however, relative atomic masses were used by scientists trying to organise the elements. This was mainly because the idea of atoms being made up of smaller sub-atomic particles (protons, neutrons and electrons) had not been developed. Nevertheless, the basis of the modern periodic table was well...
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...of those things that we’re really unsure about what it can do. Antimatter may lead mankind to new inventions ranging from teleportation, a new power source or maybe even the cure to cancer. Scientists have just scratched the surface of the abilities of antimatter. First of all, Antimatter is not fake (NASA 1). “Paul Dirac predicted the existence of antimatter in 1931” (Hooper 8). So what is antimatter? “Antimatter is matter with its electrical charge reversed”(NASA 5). An electrical charge is a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter produces and also is influenced by electromagnetic fields. Antimatter is made of essentially of antiprotons, which is a normal proton with the electrical and magnetic charge reversed. Antimatter is affected by gravity. (NASA 2). Additionally when “antimatter and normal matter collide they release energy” (NASA 5). To make antimatter, scientists must get a high velocity electron , at the speed of 96% of the speed of light, and then throw it at something, preferably with a high atomic number. After a complicated reaction, scientists either get a pion (subatomic particle) or antimatter! This cost 25 billion kWh (kilowatt-hour ) to make just one single gram. Even though the cost is massive, there is a possibility that antimatter can be used to exam or cure patients in the hospitals (NASA 3). Antimatter can be applied in neuroimaging, oncology, and infectious diseases, etc...
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...play a vital roles in physiology, they include, cobalt (Co), copper (Cu), fluorine (F), and iodine (I) Define the term ‘atom’. Discuss the structure of an atom including A) the name of the 3 major types of subatomic particles, B) the electrical properties of each of these subatomic properties, and C) the arrangement of these subatomic particles in the atom including a brief description of electron shells or energy levels. An atom is the smallest unit of an element which consists of a proton (P), neutron (n) and an electron (e). Protons are positively charges, electrons are negatively charged and neutrons have no charges i.e. are neutral. Both the proton and neutron are located inside the nucleus while the electron is located outside the nucleus. Electrons have low mass compared to the weight of the protons and neutrons inside the nucleus. Electrons determine the chemical properties of an atom .the number of protons equals the number of electrons an element has. The charges of the positive protons cancel out with the charges of the negative electrons and atom...
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...Bio 105 - Homework Chapter 2 1. Atoms are a small unit of matter that retains the properties of an element. Atoms consist of positive protons and neutral neutrons which make a nucleus, and negatively charged electrons which orbits around the nucleus in a clouds. Protons Neutrons Electrons Charge Positive Neutral negative Location in atom Nucleus Nucleus Cloud/shell Size Same as neutrons smaller than electrons About the same as a proton Smaller than both protons and neutrons Function They determine the element Stabilize the atom Participate in bonding between atoms 2. Oxygen (O) 65.5%, Carbon (C) 18.5%, hydrogen (H) 9.5%, nitrogen (N) 3.3%, 3. The outer shell always wants to be full with electrons. 4. Isotopes have the same...
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