Chapter 3 Dalton


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Chapter 3 Dalton

  1. 1. The Atom: From Philosophical Idea to Scientific Theory <ul><li>Laws of Chemistry developed in late 1700’s </li></ul><ul><li>Dalton’s Atomic Theory </li></ul><ul><li>Relating Dalton’s ideas to the new laws of chemistry </li></ul>
  2. 2. The world in the late 1700’s <ul><li>Revolutions eliminate monarchies </li></ul><ul><li>Invention of metric system </li></ul><ul><li>New belief that the natural world was understandable, rational, not only through faith, but through science </li></ul><ul><li>Improved technology allows for better quantified data collection </li></ul>
  3. 3. Laws of Chemistry known by 1790 <ul><li>Law of Conservation of Mass </li></ul><ul><ul><li>Matter is neither created nor destroyed in chemical reactions. </li></ul></ul><ul><li>Law of Definite Proportions </li></ul><ul><ul><li>Compounds always have the same composition by mass, no matter the size of the sample </li></ul></ul><ul><ul><li>Example: Salt is 39% sodium, 61% chlorine by mass, always! </li></ul></ul><ul><li>Law of Multiple proportions </li></ul>
  4. 4. Law of Multiple Proportions <ul><li>When 2 compounds are made of the same elements, comparisons of the masses of the elements in the compounds gives a small whole number ratio </li></ul><ul><li>Text example on page 69, please follow! </li></ul><ul><li>Compare CO to CO 2 ; even before we knew the formulas, we could figure out that one had exactly twice as much oxygen as the other </li></ul>
  5. 5. John Dalton, Chemist, Teacher <ul><li>Developed a theory that accounted for the newly discovered laws of chemistry. </li></ul><ul><li>How is a theory different from a hypothesis? </li></ul>
  6. 6. John Dalton, 1808 <ul><li>Matter is made of small particles called atoms </li></ul><ul><li>Atoms of one element are all alike. Atoms of different elements are different from each other.* </li></ul><ul><li>Atoms can not be created or destroyed. ** </li></ul><ul><li>Atoms combine in simple whole number ratios to form chemical compounds </li></ul><ul><li>In reactions, elements are rearranged, not changed. </li></ul>
  7. 7. Updates to Dalton’s theory <ul><li>*Not all atoms of an element are identical in all properties! Ions have a charge, and different isotopes have different masses. </li></ul><ul><li>**Atoms can be destroyed! They can not be destroyed through chemical means, but nuclear physicists dismember atoms using accelerators; atomic bombs split atoms, too </li></ul>
  8. 8. We still agree with most of Dalton’s statements. We agree that… <ul><li>All matter is made of atoms </li></ul><ul><li>Atoms of a given element all have the same number of protons. A sample of an element has an average atomic mass and a density that are characteristic of that element. </li></ul><ul><li>Atoms can not be subdivided, created or destroyed by chemical means. </li></ul><ul><li>Atoms do combine in whole number ratios to form compounds. </li></ul><ul><li>In reaction, elements are combined, separated or rearranged. </li></ul>
  9. 9. Validating Dalton’s Atomic theory with the Laws of chemistry <ul><li>The law of Conservation of Mass can be explained by Dalton’s assertion that atoms can not be destroyed, and that in chemical reactions, they are only rearranged </li></ul><ul><li>The law of definite proportions can be explained by Dalton’s idea that atoms of a particular element always have the same properties, and will therefore always combine basically the same way </li></ul><ul><li>The law of multiple proportions fits with Dalton’s idea that elements combine in simple whole number ratios </li></ul>
  10. 10. Homework due next time <ul><li>Read chapter 3 up to the end of Section 2 </li></ul><ul><li>Page 71: Section Review 1-3 </li></ul><ul><li>Page 76: #1, 3, 5 </li></ul><ul><li>Page 90: #32 </li></ul>