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Comparing Atoms

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  1. Comparing Atoms

  2. REVIEW 1 type of matter 2 or more types of matter

  3. OUR FOCUS in CH 4-7 1 type of matter 2 or more types of matter

  4. Copper Lab Steps 1 - 8 • Started outDEEP MAROON / RED • Mass crucible 25.078 g • Mass of crucible & Cu 26.558 g • Heat Copper (2 min) re-mass ???? What happened to the mass????

  5. Copper Lab Steps 1 - 8 • Started outDEEP MAROON / RED • Mass crucible 25.078 g • Mass of crucible & Cu 26.558 g • Heat Copper (2 min) re-mass 26.572 g+ + + + Ended solid BLACK A major change!

  6. The red substance “rainbowed”, changed to black and gained mass. These three indicate the substance underwent a • Chemical change • Physical change • Neither

  7. Steps 9-12 • Heat 15 min. longer • Hard solid formed– hard to remove from the bottom of the crucible • Some red still visible on the bottom side – mostly black though

  8. DAY 2 – Part A • Observations: • Some still black and some still red • Red is the original copper that has not reacted. • Black – is copper that reacted with ???? Oxygen in the air

  9. The black and red substance you broke up in the bottom of the crucible and transferred to an empty test tube was • A pure substance • A mixture of substances

  10. The red substance by itself was • A pure substance • A mixture

  11. The red pure substance is a(n) • Element • Compound

  12. Copper An element

  13. The black substance by itself was • A pure substance • A mixture

  14. The black substance by itself is a(n) • Element • compound

  15. Copper II Oxide A compound

  16. 2 Cu + O2 2 CuOWhich is/(are) elements? • Cu and CuO • O and CuO • Cu only • O only • CuO only • Cu and O

  17. 2 Cu + O2 2 CuOWhich is/(are) compounds? • Cu and CuO • O and CuO • Cu only • O only • CuO only • Cu and O

  18. DAY 2 – Part A • Solution saved for part B • Mass the solid particles remaining from the HCl solution. • Mass – the copper quantity has decreased. • Where is the copper? GREEN Copper now in the Solution NOTE: a completely different phase of matter.

  19. Which substance was soluble in HCl? • Cu – red substance • CuO – black substance • Neither was • Both were

  20. solution unreacted CuO + HCl  CuCl2 + H2O + Cu Elements – Cu Compounds - CuO HCl CuCl2 H2O Which is/(are) elements?...compounds?

  21. DAY 2 – Part B • Zinc added to “saved solution” • Bubbles • Bubbles • Bubbles • Color change • Red stuff precipitates • Physical or Chemical Change? Chemical

  22. DAY 2 – Part B • Reaction completed • Observe what is left • Identify - COPPER • Color - REDDISH • Squishy - YES

  23. (Solution) What Happened? Zinc replaces copper in the solution and copper precipitated out CuCl2 + Zn ZnCl2 + Cu

  24. CuCl2 + Zn ZnCl2 + CuWhich is/(are) elements? • CuCl2 and Cu • CuCl2 andZnCl2 • Zn and ZnCl2 • Zn and Cu

  25. CuCl2 + Zn ZnCl2 + CuWhich is/(are) compounds? • CuCl2 and Cu • CuCl2 andZnCl2 • Zn and ZnCl2 • Zn and Cu

  26. (Solution) CuCl2 + Zn ZnCl2 + Cu Zinc replaced copper in the solution

  27. Neither Heating nor other means breaks down copper • ELEMENT • True of all elements! Pure substance with one type of atom. • LIME=?? • 1800 Battery • 1807=H.Davy used battery to decompose (electrolyze) metal oxides (= Ca) • Later Muriatic Acid broken down to find Cl

  28. Today’s Element List • 50 commonly used • 10 = 99% of the mass of the Earth (5=92%) (O,Si,H, Al, Fe, Ca,Na,Mg, Cl,K)

  29. Scientists to Know … CHADWICK THOMSON RUTHERFORD DALTON de BROGLIE BOHR

  30. Bellringer When scientists wanted to find out what an atom was, they were not able to look directly at what the atom was made of. They had to make inferences from the results of many different experiments. It was like trying to describe a picture, such as the one on the next slide, with only small portions visible.

  31. Bellringer, continued 1. Write four sentences describing what you can see of the above picture. 2. What information or parts of the picture would make your descriptions more accurate without revealing the entire picture?

  32. The Beginnings of Atomic Theory • Who came up with the first theory of atoms? .

  33. Democritus • 1st to “think” of atoms • Derived from Greek word – “unable to be divided” (indivisible) • Called them - atomos • 4th century BC Democritus did not have evidence for his atomic theory.

  34. John Dalton • 1808 • Atoms are tiny hard spheres • Created the atomic theory. • All atoms of a given element are alike • Atoms of elements could join to form compounds Educated himself age 12 became a school teacher

  35. Dalton’s Atomic Theory, continued • Dalton used experimental evidence. • Law of definite proportions:Achemical compound always contains the same elements in exactly the same proportions by weight or mass. Dalton’s theory did not fit all observations.

  36. Atomic Theory through Time 400 BC Democritus • John Dalton: • D. Mendeleev: organizes periodic table 1897 JJ Thompson • ErnestRutherford • Niels Bohr 1923 Louis de Broglie 1932 James Chadwick

  37. Because of Mendeleev!!! In 1898 … W. Ramsay and M. Traves find Krypton, Neon and Xenon within 3 months using periodic table

  38. 1700s = indirect evidence of atoms • 1st real proof atom’s existed (1905) Einstein calculations of Brownian motion, heat as atomic motion and momentum conservation.

  39. Atomic Theory through Time 400 BC Democritus • John Dalton: • D. Mendeleev: organizes periodic table 1897 JJ Thompson • ErnestRutherford • Niels Bohr 1923 Louis de Broglie 1932 James Chadwick

  40. JJ Thomson • experimented with currents of electricity inside empty glass tubes. • PLAY THE SEGMENT FROM THE CD

  41. JJ Thomson • experimented with currents of electricity inside empty glass tubes. • Discovered • electron in every atom • electrons have a negative charge • “Plum-pudding” model

  42. Ernest Rutherford Geiger and Marsden Lab 18.1 – Gold Foil Experiment PLAY THE SEGMENT FROM THE CD

  43. Rutherford •  particles • most passed straight through • Atom mostly empty space ! • some scattered at large angles • Center positively charged nucleus

  44. Niels Bohr Electrons in an atom move in a set path around the nucleus / similar to planets around the sun Electrons orbit the nucleus in fixed orbits Orbits have fixed amount of energy

  45. Louis de Broglie • By 1925 Bohr’s Model was altered. • Electrons behave more like waves on • a vibrating string • analyzed a moving particle as a wave

  46. James Chadwick • Research focused on radioactivity. • With Rutherford – knew there had to be another particle with the proton in the nucleus (missing mass) • discovered neutron • neutrons are the missing mass in the atom

  47. Atom • 1955 • Mueller – Professor at Penn State • 1st to see an atom with an ion microscope • synthetic Metals (???)

  48. Atoms broken down further • Nucleus– Center of atom: Dense • Protons and Neutrons: similar in size and mass • Protons – positive charge • Neutrons – no electric charge • Outside the Nucleus • Electrons – cloud of tiny particles with little mass • Electrons – negative charge (-1) • Size – nucleus : marble – distance to electrons : stadium

  49. Relative Size of Atoms • Atom : Person as Person : Ave. Star • Atom : Apple as Apple : Earth (picture apple full of atoms and then Earth full of apples)