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Matter Class #3

Matter Class #3 OB: Principles of separating mixtures, counting atoms in chemical formulas, and the indicators of chemical reactions. First we count. How many atoms, what atoms are in each of these? H 2 O ___________ NaCl ___________ CO 2 ___________

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Matter Class #3

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  1. Matter Class #3 OB: Principles of separating mixtures, counting atoms in chemical formulas, and the indicators of chemical reactions

  2. First we count. How many atoms, what atoms are in each of these? H2O ___________ NaCl ___________ CO2 ___________ HCl ___________ H2SO4 ___________ MgO ___________

  3. First we count. How many atoms, what atoms are in each of these? H2O = 2 hydrogen atoms + 1 oxygen atom = 3 NaCl = 1 sodium atom + 1 chlorine atom = 2 CO2 = 1 carbon atom + 2 oxygen atoms = 3 HCl = 1 hydrogen atom + 1 chlorine atom = 2 H2SO4 = 2 hydrogen atoms + 1 sulfur atom + 4 oxygen atoms = 7 MgO = 1 magnesium atom + 1 oxygen atom = 2

  4. These are harder, how many atoms of each kind, how many all together in each compound? Fe2O3 H3PO4 KHCO3 Li2C2O4 Ca(OH)2 Al(OH)3 Al2(Cr2O7)3 (NH4)2SO3

  5. These are harder, how many atoms of each kind, how many all together in each compound? Fe2O3 H3PO4 KHCO3 Li2C2O4 Ca(OH)2 Al(OH)3 Al2(Cr2O7)3 (NH4)2SO3 8 = 3 H + 1 P + 4 O 5 total = 2 Fe + 3 O • 6total = K + 1 H + 1 C + 3 O 8 = 2 Li + 2 C + 4 O 7 = 1 Al + O + H + O + H + O + H (three times!) 5 total = 1 Ca + O + H and O + H again 29 = 2 Al + 2 Cr + 7 O and2 Cr + 7 O and2 Cr + 7 O again (three times!) • 14 = N + 4 H + N + 4 H + 1 S + 3 O

  6. Practice those on the Elements + Matter Handout due by Friday. Principles of separating mixtures… Mixtures are just physical blends of pure substances, they could be Elements + Elements, or Elements + Compounds, or Compounds + Compounds, etc. These pure substances, elements or compounds, retain their unique properties in the mixture. No new stuff forms, just stir these things together.

  7. Since they are just physically mixed, you should be able to separate them with just physical means (not chemical). For instance, to separate the mixture of sand and water, you could filter them apart. The “principle” that allows us to do this is that the sand is much bigger than the water particles, and sand gets stuck in the filter paper. We… TAKE ADVANTAGE OF A DIFFERENCE IN PHYSICAL PROPERTIES.

  8. What if you mix up salt with water? How could you get them apart? Take advantage of the difference in BOILING POINTS between the water and the sodium chloride. PURE WATER Salty water HEAT!!!

  9. Separating mixtures requires thinking, and taking advantage of differences in physical properties… Here, iron is separated from what appears to be sulfur, taking advantage of the magnetic attraction of iron and not the sulfur.

  10. You could also separate mixtures by taking advantage of differences in Freezing Points, Density, Melting Points, Etc.

  11. TOPIC-B We need to watch for chemical reactions in our upcoming lab. There are several indicators (or indications) that a chemical reaction has happened. Indicators are a heads up, not PROOF. Thinking is still required. The acronym TOPIC-B will help keep them in your head, where they belong.

  12. T – temperature change… if the stuff you are playing with changes temperatures (by itself, not a fridge or a Bunsen burner) a chemical reaction has probably happened. O – odor change… if the stuff you have in a test tube or beaker goes from one smell to another, or no smell to smelly, then a chemical reaction has probably happened. P – precipitate… if you mix some solutions, and all of a sudden solids fall out of the solution, then a chemical reaction has probably happened. I – irreversibility… if what you have done stays done, and does not just go back easily (like melting and freezing and melting H2O) then a chemical reaction has probably happened. C – color change… if what you mix or heat changes color, then what you had has likely become something else, or, a chemical reaction has probably happened. B – bubbles… if you mix or heat something and bubbles come out that weren’t there before, then a chemical reaction has probably happened. Soda has gas in it, even though you can’t see it, shaking soda releases the gas bubbles that were there already. New bubbles count, bubbles already there don’t.

  13. If it’s called the World Series, then why is it almost always played in the Bronx? Alex Rodriguez

  14. Finish the penny lab Finish the Elements and Matter Handout Read the Matter Diary Do the Drills Counting Atoms in Formulas Tonight!

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