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What is a pure substance that cannot be seperatedinto simpler substances by physical means
An element
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What are three examples of naturally occuring elements?
Copper, oxygen, gold
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is the first letter in the symbol always capitalized?
yes!
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how much mass of the universe does hydrogen make up?
75%
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what is one of the least abundant naturally occurring element
francium
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in _____ the russian chemist__ __ made a significant contribution to the periodic table
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how does the periodic table organize the elements
into a grid of horizontal rows called periods and vertical columns called groups or families
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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
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how many known compounds are there?
10 Million
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What is the compound for table salt
One part sodium and one part chlorine
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Unlike elements,______ can be broken down into simpler substances by chemical means
compounds
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to seperate a compound into its elements often requires external_ such as ____ or _
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the ____ of a compound are different from those of its component elements
Properties
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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
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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
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matter that has a uniform and unchanging composition is a ________
substance
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Physical properties describe ______ _________, too. because substances have uniform and unchanging compositions, they have consistent and unchanging__________ ________as well
pure substances
physical properties
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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.
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what is the difference between pyrite and gold
they are different samples of matter and the look the same byt their desity is different
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the ability of _to rust when combined with air is an example of a _____ ____________of iron
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the properties of water are _________ diferent under different conditions
dramatically
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what are four examples of solids
wood, iron, paper, and sugar
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what are examples of liquids
water, blood, and mercury
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what are examples of gases?
neon, methane, air
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how many eloements on earth occurr naturally
91
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EACH ELEMENT HAS A UNIQUE ____ANDSYMBOL
name
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the 91 naturally occurring elements are not equally ________
abundant
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__ and___ together comprise almost_ of the mass of earths crust, while oxygen, carbon, and hydrogen account for more than _ of the human body
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how much of the above element is dispersed throughout the earths crust
20 grams
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how did dmitri mendeleev organize the periodic table
he made a chart of rows and columns based on their similarities and masses
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what was the BRILLIANT aspect of Mendeleevs original table
it structure could accomodate elements that were not known at the time
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what is a compound
a combination of two or more different elements that are combined chemically
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______ that naturally occurr are more stable than the individual comonent elements
compounds
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what is the percent by mass equation?
- %=mass of element *100
- mass of compound
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changes which alter a substance without changing its composition are __________ changes
physical
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as _____ and _____ change most substances undergo a change from one state to another
temperature and pressure
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a _ is a combination of two or more pure substances in which each pure substance retains it idividual chemical _____
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