Chemical reactions and molecules

Chemical reactions and molecules - representations of how...

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Chemical reactions and molecules Molecules are compounds in which the elements are in definite, fixed ratios, as seen in Figure 12. Those atoms are held together usually by one of the three types of chemical bonds discussed above. For example: water, glucose, ATP. Mixtures are compounds with variable formulas/ratios of their components. For example: soil. Molecular formulas are an expression in the simplest whole-number terms of the composition of a substance. For example, the sugar glucose has 6 Carbons, 12 hydrogens, and 6 oxygens per repeating structural unit. The formula is written C 6 H 12 O 6 . Figure 12. Determination of molecular weights by addition of the weights of the atoms that make up the molecule. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates and WH Freeman used with permission. Chemical reactions occur in nature, and some also can be performed in a laboratory setting. One such reaction is diagrammed in Figure 13. Chemical equations are linear
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Unformatted text preview: representations of how these reactions occur. Combination reactions occur when two separate reactants are bonded together, e.g. A + B -----> AB. Disassociation reactions occur when a compound is broken into two products, e.g. AB -----> A + B. Figure 13. Diagram of a chemical reaction: the combustion of propane with oxygen, resulting in carbon dioxide, water, and energy (as heat and light). This chemical reaction takes place in a camping stove as well as in certain welding torches. Image from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates and WH Freemanused with permission. Biological systems, while unique to each species, are based on the chemical bonding properties of carbon. Major organic chemicals (those associated with or formed by the actions of living things) usually include some ratios of the following elements: C, H, N, O, P, S....
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Chemical reactions and molecules - representations of how...

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