CH 304K 1st Edition Lecture 5 Outline of Last Lecture I. Atmosphere, Temperature, and PressureOutline of Current Lecture II. Physical vs. Chemical changesIII. Introducing Atoms and MoleculesIV. CompoundsV. Periodic TableCurrent LecturePhysical Changes- Not changing the parts- Examples: melting, freezing, ripping, Chemical Changes- Afterwards, there is a different substance than you started with- Examples: setting paper on fire, leaving a sandwich in a car for a weekendIntroducing Atoms and Molecules- Ancient Greece- Democritus determined that if you infinitely dissect a pure substance, you get something “uncuttable” or “Atomos”- about 90 atoms exist naturally, the rest are man-made- elements consist of ONE type of atom- compounds contain two or more types of atoms- Law of Conservation of Matter: In chemical reactions, we cannot create or destroy atoms, only change how they are arrangedThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Law of Constant Composition: For a given pure substance all molecules have the same number and type of atoms- Diatomic Molecules: Br I N Cl H O F- Some elements exist as polyatomic molecules because they are more stable that way- Polyatomic molecules: P4, S8, O3- Allotropes: more than one form of the element exist (example: oxygen)Compounds- Molecular or ionic- Organic or inorganicMolecular Compounds- Exist as discrete molecules - Molecular formula tells how many atoms of each type of element (example: H2O)Ionic Compounds- Do not exist as discrete molecules, exist as crystalsOrganic vs. inorganic- Organic: contains C, H and sometimes N, S, O- Inorganic: generally do not contain C-H bondsPeriodic Table- Patterns- Dimitri Mendeleev and Lothar Meyer ordered elements by mass and emphasized chemical properties- Groups are verticle, periods are
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