chemical Reactions DS

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Chemical Reactions

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chemical Reactions DS

  1. 1. Elements, Atoms, Compounds and Molecules<br />By Darcy p. Simonsen<br />
  2. 2. Element <br />A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number. <br />Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, nitrogen, and oxygen. In total, 117 elements have been observed as of 2008, of which 94 <br /> occur naturally on Earth<br />
  3. 3. Atom<br />The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.<br />
  4. 4. metals<br />a metal is an element, compound, or alloy characterized by high electrical conductivity . In a metal, atoms readily lose electrons to form positive ions; those ions are surrounded by delocalized electrons, which are responsible for the conductivity.<br />
  5. 5. Non metals <br />non-metal is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a nonmetal.<br />
  6. 6. The periodiс table of the chemical elementsis a tabulardisplay of the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended <br />the table<br />Periodic table <br />
  7. 7. Compounds <br />A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions and that have a unique and defined chemicalstructure.<br />
  8. 8. Chemical reactions <br />A chemical reaction is a process that leads to the transformation of one set of chemical substances toanother. There are three things that speed up chemical reactions one of them are:<br />
  9. 9. chemical and physical changes <br />1. A physical change is reversible, a chemical change is not. For example, the freezing of water would be a physical change because it can be reversed, whereas the burning of wood is a chemical change - you can&apos;t &apos;unburn&apos; it. <br />
  10. 10. Identifying chemical reactions <br />There are three types of chemical reactions, here are two:<br />Synthesis<br />A synthesis reaction is when there is a combination of two or more substances and a compound results. An example A + B --&gt; AB<br />Decomposition<br />Decomposition is roughly the opposite of synthesis it is a breaking down of one molecule into two (or more) smaller molecules or elements. <br />Sample decomposition reactions could include:<br />2 H2O + electricity -&gt; 2 H2 + O2<br />
  11. 11. make a reaction faster <br />use a catalyst<br />breaking a solid into something smaller<br />(to increase its surface area) <br />make the solution more concentrated, <br />increase the temperature. <br />
  12. 12. Bibliography <br />Wikipedia the free encyclopaedia <br />Google images <br /> What is the difference between a physical change and a chemical...<br />

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