chemistry

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Anonymous
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47087
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chemistry
Updated:
2010-11-03 14:59:59
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Kacie Gabby
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chemistry test
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  1. What is a pure substance that cannot be seperatedinto simpler substances by physical means
    An element
  2. What are three examples of naturally occuring elements?
    Copper, oxygen, gold
  3. is the first letter in the symbol always capitalized?
    yes!
  4. how much mass of the universe does hydrogen make up?
    75%
  5. what is one of the least abundant naturally occurring element
    francium
  6. in _____ the russian chemist__ __ made a significant contribution to the periodic table
    • 1869
    • dmitri mendeleev
  7. how does the periodic table organize the elements
    into a grid of horizontal rows called periods and vertical columns called groups or families
  8. how was he able to predict the properties of elements that were not yet discovered?
    By analyzing the similarities among the elements and their pattern of repitition
  9. how many known compounds are there?
    10 Million
  10. What is the compound for table salt
    One part sodium and one part chlorine
  11. Unlike elements,______ can be broken down into simpler substances by chemical means
    compounds
  12. to seperate a compound into its elements often requires external_ such as ____ or _
    • energy
    • heat
    • electricity
  13. the ____ of a compound are different from those of its component elements
    Properties
  14. what is the law of definite proportions?
    regardless of the amount a compound is always composed of the same elements in the same proportion by mass
  15. what is the law of multiple proportions
    when different compounds are formed by a combination of the same elements different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers
  16. matter that has a uniform and unchanging composition is a ________
    substance
  17. Physical properties describe ______ _________, too. because substances have uniform and unchanging compositions, they have consistent and unchanging__________ ________as well
    pure substances

    physical properties
  18. explain how intensive physical properties were used during the california gold rush?
    Miners relied on gold characteristic density to seperate valuable gold containing flakes from riverbed sand.
  19. what is the difference between pyrite and gold
    they are different samples of matter and the look the same byt their desity is different
  20. the ability of _to rust when combined with air is an example of a _____ ____________of iron
    • iron
    • air
    • chemical property
  21. the properties of water are _________ diferent under different conditions
    dramatically
  22. what are four examples of solids
    wood, iron, paper, and sugar
  23. what are examples of liquids
    water, blood, and mercury
  24. what are examples of gases?
    neon, methane, air
  25. how many eloements on earth occurr naturally
    91
  26. EACH ELEMENT HAS A UNIQUE ____ANDSYMBOL
    name
  27. the 91 naturally occurring elements are not equally ________
    abundant
  28. __ and___ together comprise almost_ of the mass of earths crust, while oxygen, carbon, and hydrogen account for more than _ of the human body
    • oxygen and silicon
    • 75%
    • 90%
  29. how much of the above element is dispersed throughout the earths crust
    20 grams
  30. how did dmitri mendeleev organize the periodic table
    he made a chart of rows and columns based on their similarities and masses
  31. what was the BRILLIANT aspect of Mendeleevs original table
    it structure could accomodate elements that were not known at the time
  32. what is a compound
    a combination of two or more different elements that are combined chemically
  33. ______ that naturally occurr are more stable than the individual comonent elements
    compounds
  34. what is the percent by mass equation?
    • %=mass of element *100
    • mass of compound
  35. changes which alter a substance without changing its composition are __________ changes
    physical
  36. as _____ and _____ change most substances undergo a change from one state to another
    temperature and pressure
  37. a _ is a combination of two or more pure substances in which each pure substance retains it idividual chemical _____
    • mixture
    • properties

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