Elements, compounds, mixturesand intro to sigfigs

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Elements, compounds, mixturesand intro to
sigfigs
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Elements and Compounds

• Element
• Substances that only contain one type of atom
• Examples Pure Aluminum, Pure Copper
• Compound
• Substances that contain two or more different
  types of atoms
• Examples Water (H2O) Carbon Dioxide (CO2)

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Mixtures and Pure Substances

• Mixtures-
• Something that has variable composition
• Examples Air, Soda pop, coffee, alloys, sea
  water
• (Alloy mixtures of metals)
• Who has heard of alloy wheels?
• Pure Substance-
• Something that always has the same composition
• Examples Water (H2O), Oxygen, Nitrogen

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Homogeneous Heterogeneous Mixtures

• Homogeneous Mixture
• Is the same throughout
• Also called a Solution
• Examples Air, Processed Milk, others
• Heterogeneous Mixture
• Contains regions that have different properties
  from those of other regions.
• Examples Cold Stone Ice Cream, yogurt with fruit
  on the bottom, Milk straight from the cow,

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Separation of Mixtures

• Distillation
• Apparatus that separates contaminates in water
  based on phase changes
• Filtration
• A mesh that allows the liquid to pass through and
  leaves the solid behind.
• How could we get sand out of water?
• How could we separate the salt from Sea Water to
  get drinkable water?
• How do we get the fruit out of our yogurt?

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Significant Figures

• Used for making measurements
• Tells you the accuracy of the measuring device
• This can be a ruler, graduated cylinder, triple
  beam balance, etc.
• You always measure 1 digit beyond what the
  measuring device has.

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Significant Figures cont

• Example 1
• This ruler measures to the .1 (in this case
  centimeters)
• However, I can see that the measurement lies
  between the 2.8 and 2.9 measurement, so I can
  make the estimate that it is approximately 2.83
  cm.
• You see!!! All of those numbers are significant,
  because they all tell me about the measurement!
• If I went out any further, it would not be
  accurate, because my measuring device is not that
  accurate!

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Significant Figures cont

• Example 2
• This ruler indicates the measurement is 4.5 on
  the nose, so I say it is 4.50 cm to indicate that
  it is directly on 4.5!

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Significant Figures cont

• This works for other measuring devices as well.
  Just remember to always go one digit further than
  the device does
• Example 1
• What is the temp on the thermometer on the left
  indicate?
• The thermometer has whole number digits , so for
  sig figs I can go to the tenths.
• The temp is 28.5oC

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Significant Figures cont

• This also works for Graduated Cylinders
• Example 1
• The drawing below indicates you are looking at a
  graduated cylinder from the side (note the dip or
  meniscus, which you always read from the bottom)
• This graduate cylinder measure to the whole
  number so we will read it to the tenth
• This graduated cylinder has a reading of 30.0 ml

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Significant Figures

• Rules for significant figures
• 1) Count all non-zero integers
• Example the number 1234 has 4 significant
  figures.
• 2) How to count zeros
• Leading zeros never count as significant figures
• Example .00032 has only 2 significant figures
• Captive zeros always count as significant
  figures
• Example. 1.003 has 4 significant figures
• Trailing zeros Count only if the number is
  followed by a decimal point
• Example 100 has 1 significant figure 100. has 3

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Significant Figures cont

• 3. Exact numbers unlimited number of significant
  figures
• Because they are exact- you can use these without
  ever rounding

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Significant Figures cont

• Examples How many significant figures in the
  following
• .0018
• .00108
• 10800
• 10800.
• .1080

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Homework

• Iron Reading and questionsDue Tuesday