SES194 Energy in Everyday Life
SES194 Energy in Everyday Life SES194
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This 6 page Bundle was uploaded by Sarah Booth on Tuesday October 4, 2016. The Bundle belongs to SES194 at Arizona State University taught by Frank Timmes in Fall 2016. Since its upload, it has received 7 views. For similar materials see Energy in Everyday Life in Business at Arizona State University.
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Date Created: 10/04/16
SES194 Energy in Everyday Life Unit 2 Chemical Energy Chemical energy plays a crucial role in each and every one of our daily lives. -Through chemical reactions, the breaking and forming of chemical bonds, energy can be extracted and harnessed in a usable fashion. -Many of the chemical compounds used to produce energy involve burning - oxidation reactions. Sarah Booth -Gasoline powers most automobiles and trucks. -Kerosene serves as jet fuel. -Natural gas, coal, and oil are burned to heat our homes and produce electricity. -The root source of the energy used for heating, transportation and industry in the most of the world is chemical energy. -Chemical energy is also the basis for the processes of life. Example The chemical energy in food is converted by organisms into mechanical energy and heat. -Chemical reactions involve the making and breaking of chemical bonds. -The chemical energy of a system is energy released or absorbed due to making and breaking of these bonds. Breaking bonds absorbs energy. Forming bonds releases energy. Sarah Booth SES194 Energy in Everyday Life Unit 2 Atomic Structure In any chemical reaction there is a change in the condition of the constituents of the atoms involved. -If we take a material and shrink our ﬁeld view, we would eventually identify what seems like an impenetrable shell.We would be looking at the outer surface of an atom. -This surface is provided by the atoms electrons.A typical diameter is 101m. -Everyday matter is made of atoms which are made from protons, neutrons and electrons. -Atoms of different chemical elements have a different number of protons. Isotopes of an element have the same number of protons but a different number of neutrons. Sarah Booth -Molecules are made of two or more atoms. A diagram of the water molecule (H O) is2 shown to the right. -Although the electrons are wavelike and not localized in space, they do have a high probability of being near positions they would occupy if they were particles. -Negatively charged electrons repel each other electrically, just as they are attracted to the positive charge of the nucleus, but they cannot all get close to the nucleus. These are multiple electron paths around the nucleus. -We ﬁnd experimentally that no two electrons may exist in the same state (distance, energy, etc) in an atom (just like a snowﬂake!) -The outermost electrons, the valence electrons provide what we consider to be the outer surface of the atom, the “size”.The yellow dots on the image represent the valence electrons. Sarah Booth SES194 Energy in Everyday Life Unit 2 Atomic Energy Levels Electrons take up “positions” (orbitals or shells) around the nucleus.The ﬁrst electrons occupy the lowest energy rungs, giving up the most energy to become part of the atom. -Subsequent electrons added to the atom give up less energy and are more easily removed from the atom. Example As an analogy, consider a eucalyptus tree with pair of leafy branches going up a tree trunk and koalas eating the leaves. Because koalas have a mass we imagine that they would break the branches if more than 1 koala sits on a branch. Since each branch can hold only one koala, a new koala climbing the tree would have to climb to the next available free branch to have a perch on which to eat the tree leaves. Likewise, electrons in atoms are found by the exclusion principle to take “positions” higher in energy levels than those already there. Sarah Booth -Electrons can only exist at speciﬁc energy levels in an atom. -Electrons going from one level to another only occurs when an electron gains or loses just the right amount of energy. -Emission or absorption of light only occurs at speciﬁc wavelength that correspond to speciﬁc energy level transitions in atoms or molecules. -Every element produces a unique set of spectral lines so we can determine the composition by identifying these lines. Examples: -Thermal -Neon -Hydrogen (as seen above) -Iron -Helium -Silicon Sarah Booth
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