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Chemistry Ch. 2, 4

Chemistry Ch. 2, 4. Ch. 2. *Physical Properties: A quality that can be observed without changing the substance’s composition. *Chemical Property: Describes the new substances that a substance can make. *Physical Change: Something changes, but it is still the same substance.

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Chemistry Ch. 2, 4

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  1. Chemistry Ch. 2, 4

  2. Ch. 2 • *Physical Properties: A quality that can be observed without changing the substance’s composition. • *Chemical Property: Describes the new substances that a substance can make.

  3. *Physical Change: Something changes, but it is still the same substance. • *Chemical Change: A new substance(s) is formed.

  4. Mg + HCl

  5. Hints that a chemical change occurred: • -Color Change • -Change in temperature • -Gas released

  6. Mixtures Two or more things mixed together. • Heterogeneous mixture The composition is NOT uniform throughout. • Homogeneous mixture AKA Solution The composition is uniform throughout.

  7. *Conservation of Mass The mass of the reactants always equals the mass of the products in a reaction.

  8. Ch. 4 • Atom: The smallest particle of an element that retains the properties of the element.

  9. Democritus’s atomic principle (400 BC) Atoms are indivisible and indestructible.

  10. *Dalton’s atomic theory (1800) • 1. All elements are composed of atoms • 2. The atoms of one element are different from the atoms of any other element. • 3. Atoms can combine to form compounds. • 4. In chemical reactions, atoms can be rearranged, but an atom can never change into a different type of atom.

  11. Atoms can be viewed with instruments like scanning tunneling microscopes.

  12. Electrons Negatively charged particles. • Cathode ray tubes were used by Thomson to discover the electron.

  13. Protons + charged particle in the nucleus. Discovered by Goldstein. • Neutron No charge, in the nucleus. Found by Chadwick.

  14. Rutherford’s gold foil experiment (1911) • Found that most of the atom is empty space, with a small, positively charged nucleus.

  15. Rutherford model of the atom Nucleus with protons and neutrons, electrons super far from the nucleus.

  16. *Atomic Number: The number of protons in an atom. (It also tells you the number of electrons in the atom for a NORMAL atom) • Each Element has a unique atomic number.

  17. *Mass Number: Protons + Neutrons in an atom. • And remember, atomic number = # protons. • If an atom has 4 protons and 5 neutrons, mass number = 9.

  18. *Isotopes • Atoms with the same number of protons, but a different number of neutrons. • Hydrogen—1 vs. Hydrogen—3

  19. Shorthand notation • Carbon—13 • 136C • How many protons? Electrons? Neutrons? • Bromine—80 • 8035Br • How many protons? Electrons? Neutrons?

  20. How many electrons, protons, neutrons?

  21. Atomic mass Measured in amu • Amu= the mass of one twelvth of a carbon—12 atom).

  22. Atomic mass is a weighted average. • There is 98.89 % Carbon—12, and 1.11% Carbon—13. Calculate the amus for carbon. • (.9889 * 12.0 amu) + (.0111 * 13.0 amu) • 12.0 amu

  23. If Rb—85 has an abundance in the universe of 72.2% and Rb-87 has an abundance in the universe of 27.8%, what is the average atomic mass of Rubidium?

  24. Draw out B—11

  25. Periodic Table • Periods go across. The properties of elements varies as you go across the table. • Groups go up/down. *The elements in the same group have similar chemical and physical properties.

  26. Elements in the same group have the same amount of valence electrons.

  27. Isotope Drawing Activity • Draw out 3 isotope pairs coming from P, C, and Mg. Make a key that states what color protons, neutrons, and electrons are. • Color and Label everything nice. Nothing should be done in pencil.

  28. Drawing activity: Draw out the following isotopes of Carbon. • Carbon-12, Carbon-13, Carbon-14 • Protons = Red, Neutrons = Blue Electrons = Green • Draw out and explain Thomson’s experiment that led to the discovery of the electron.

  29. Chemical Change Lab, Next Slide

  30. A Chemical Change Lab: • A. Write down your observations. B. Write down any clues that a chemical change occurred. C. Write down if you think it was a chemical or physical change and why. • Need: (Arrange these into stations) • 1.) Phenolphthalein/HCl, combine with NaOH • 2.) Regular / Torn Paper • 3.) Food Coloring / Beaker / Water / Stir Bar/ Hot Plate • 4.) Egg / Vinegar http://www.kidzone.ws/science/egg.htm • 5.) Copper and Aluminum in Coca Cola • 6.) Video of an alkali metal reacting with water. (Laptop) • 7.) Egg / Hydrochloric Acid • 8.) Egg / Sodium Hydroxide • 9.) Questions on Powerpoint • 10.) Questions on Powerpoint 11.) Video on Ipad

  31. 9a. Think of 3 chemical changes that you’ve seen in real life. • 9b. Think of 3 physical changes you’ve seen in real life. • 9c. What is the difference between a chemical and a physical change?

  32. 10a. What kind of mixture is the air in this room? Heterogeneous or homogeneous? Explain why. • 10. b. Think of 2 heterogeneous mixtures in real life and 2 homogeneous mixtures in real life.

  33. Carry out 1-3 and write down your observations for each: • 1. Into a beaker, Put 5 dirty pennies in vinegar, and put 5 pennies in a baking soda solution in another beaker. Stir and let sit. Observe the pennies at the end of lab. • 2. Get a bunsen burner going. Hold a wire mesh cage with a tongs over the flame. Observe. • 3. Get some slightly acidic water. Put 2 drops of phenolphthalain in it. Now add NaOH slowly until a color change occurs. • 4. Clean everything up. Talk about with Mr. Hall Why are these chemical changes?

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