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CHAPTER 2 PROPERTIES OF MATTER

CHAPTER 2 PROPERTIES OF MATTER. PURE SUBSTANCES. Matter w/ same composition throughout Table salt or sugar Every pinch tastes equally salty/sweet 2 categories: Elements compounds. ELEMENTS. substance that cannot be broken down into simpler substances.

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CHAPTER 2 PROPERTIES OF MATTER

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  1. CHAPTER 2PROPERTIES OF MATTER

  2. PURE SUBSTANCES • Matter w/ same composition throughout • Table salt or sugar • Every pinch tastes equally salty/sweet • 2 categories: • Elements • compounds

  3. ELEMENTS • substance that cannot be broken down into simpler substances. • fixed comp because it has only 1 type of atom • Cutting copper wire into smaller and smaller pieces until you end up with copper atoms • No 2 elements contain same type atom

  4. EXAMPLES OF ELEMENTS At room temp (20°C, or 68°F), most solids, some gases, 2 liquids

  5. COMPOUNDS • Substance made of 2 or more simpler substances • Can be broken down into simpler substances (elements or other compounds) • Always joined in fixed proportion • H20 – 1 drop or 1 gallon, always 2 parts hydrogen for every 1 part oxygen

  6. MIXTURES • Similar to cmpds b/c multiple substances • Different b/c properties can vary b/c composition NOT fixed • salsa – each bite has different amt of onion, pepper, etc • Pizza – each slice has diff amt toppings

  7. HETEROGENEOUS MIXTURES • parts of mixture noticeably different from one another • Sand, trail mix, Lucky Charms, Italian salad dressing

  8. HOMOGENEOUS MIXTURES • Substances evenly distributed • difficult to distinguish one substance from another • Appears to contain only one substance • Stainless steel (iron, chromium, and nickel), Kool-Aid, and pool water

  9. SOLUTIONS, SUSPENSIONS, AND COLLOIDS 3 major classifications of mixtures: Based on size of largest particles:

  10. SOLUTIONS • small particles dissolved creating a homogeneous mixture • Windshield washer fluid, sweetened tea, Kool-Aid • Particles too small to settle out, be trapped by filter, or scatter light

  11. SUSPENSIONS • Heterogeneous mixture separates into layers over time • Italian salad dressing, dirt particles in the air, quicksand • Large particles can be trapped by filter and scatter light making suspensions cloudy

  12. COLLOIDS • Intermediate size particles – larger than solution, smaller than suspension • Large enough to scatter light, too small to settle out / filtered • Milk, shaving cream, smoke, fog

  13. PHYSICAL PROPERTIES SECTION 2.2

  14. VISCOSITY • resistance to flow • High viscosity  slow flow • high visc: – honey, lava, motor oil • low visc: – water, vinegar, olive oil

  15. CONDUCTIVITY measure of material’s ability to allow flow of heat / electricity Metals  high conductivity – called conductors Wood, rubber, and styrofoam low conductivity – poor conductors

  16. MALLEABILITY Material’s ability to be hammered w/o shattering Most metals malleable ex. gold, lead, iron

  17. HARDNESS Material’s resistance to be scratched Harder substances “scratch” softer ones Grinding wheels high $ b/c Contains diamond chips

  18. MELTING & BOILING POINTS Melting point – solid to liquid Boiling point – liquid to gas These characteristics can be used to separate substances out of mixtures

  19. DENSITY Tests purity of substances Mass - volume ratio Methanol is fuel burned in some racing motorcycles. Must be 99.65% pure

  20. USING PROPERTIES TO SEPARATE MIXTURES FILTRATION Separating materials based on size of particles brewing coffee iced tea

  21. DISTILLATION When solution can’t be filtered, distillation used Distillation provides fresh water for submarines Fresh H2O and sea H2O separated b/c differences in boiling pts

  22. RECOGNIZING PHYSICAL CHANGES Physical change – some properties of a material change, but substance remains same Ex. Melting ice cream, cut hair, crumple paper

  23. CHEMICAL PROPERTIESSECTION 2.3

  24. OBSERVING CHEMICAL PROPERTIES Candle burning causes water and carbon from paraffin to turn into carbon dioxide (new substance that was not originally present) Chemical properties observed only when substances are changing into different substances

  25. FLAMMABILITY Burning in presence of OXYGEN Burning substances used as fuel Gasoline coal wood Sometimes not desirable Children’s sleepwear – low flammability Difficult to ignite Burns slowly

  26. REACTIVITY When oxygen from air reacts with iron from car & water from air…..rust forms completely new substance……… Oxygen + water + iron = iron oxide (rust) Nitrogen is less reactive – N gas used in submarine tanks to replace reactive O gas

  27. RECOGNIZING CHEMICAL CHANGES Look for: gas produced heat produced **change in color precipitate (solid) formed **Color change alone can also be a physical change

  28. IS A CHANGE CHEMICAL OR PHYSICAL? Color change as physical change…despite color change, iron is still iron Gas produced as physical change/…water boiling changes phases (liquid to gas) but still H2O

  29. PHYSICAL V.S. CHEMICAL CHANGE When matter undergoes chemical change, comp of matter changes When matter undergoes physical change, comp remains same

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