Scientific Measurements: The Metric System

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Scientific Measurements The Metric System

• Part I

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Accuracy vs Precision

• When you are accurate, you are close to the
  actual data (you dunk 8 out of 10 baskets)
• When you are precise, you are right on the
  money (you dunk 10 out of 10 baskets)

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Estimation

• When you estimate, you look at the place value
  to the right of the place value you are
  estimating to. If that number is 5 or above,
  then you will raise the place value by 1 number
•  
• Examples
• tenths 6.43 6.4 but
  6.45 6.5
• hundredths 329.152 329.15 but
  329.158 329.16
• Whole numbers 987.3 987 but 169.82
  170

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Organizing Data

• Mean, median and mode When you analyze a set of
  data
• Mean average (add up numbers and divide by the
  amount of numbers you added)
• 5 55 15 15 / 3 5
  (mean)
• median the number that represents the middle
  of the data. YOU HAVE TO PUT THEM IN ORDER FROM
  SMALLEST TO LARGEST
• 6.2, 7.5, 4.3 put in
  order 4.3 6.2 7.5 (median is 6.2)
• mode when you have a number that appears the
  most often
• 23.7, 14.9, 23.7, 66.1 mode
  23.7
• range subtract the smallest number from the
  largest 66.1 14.9 51.6

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Graphs
III. Graphs Used to visually see a change or
comparison in data   Line graph shows a change
over time  
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Bar Graphs
Bar graph shows a comparison between 2 or
more objects or event  
 
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Circle Graphs
  Circle graph uses a circle to show a
breakdown to show percentages (out of
100). Colors and patterns are often used to
show the differences.  
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Computing Percentages for a Circle Graph

• There are 360o in a circle.
• If you have 15 to shade, then
• 360 o x .15 54o
• So you would mark the 54o with a protractor.

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The Metric System
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SI Units (Metric System)

• The International System of Measurement (SI)
• The metric system (SI) used so scientists
  everywhere can communicate with each other. Based
  on the number 10.
• Major units
• Length meter
• volume liters (liquids) or centimeters (solid
  or liquid)
• mass gram/kilogram (measured by a balance
  instrument)

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Length, Mass, and Volume

• The measurement of length is used to find the
  length, width or height of an object
• The measurement of mass is the amount of matter
  that makes up the object measured in milligrams,
  grams or kilograms
• (paperclip 1g)
• Volume is the amount of space the object takes
  up.

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Mass vs Weight

• Mass is the amount of material that makes up an
  object. (tent vs house)
• Weight is completely dependent upon gravity and
  mass of the object. Since gravity varies in
  different places, then weight can change, but
  mass does not!
• http//www.youtube.com/watch?vbxZred-4_NU

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Length

• The instrument used for length is the meter
  stick.
• If you are dealing with AREA, use the 2 numbers
  of the area formula (length x width), and square
  (2) the answer 6 m x 4 m 24 m2

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Volume

• The instrument for volume can be either the meter
  stick (for a solid -like a box), or a container
  (like a bottle or container) for a liquid.
• Volume, as a solid, can be measured in meters.
• Volume, as a liquid, can be measured in liters.
• Volume can also be measured in cubic centimeters
  (cc)
• If you are finding the volume of an object, then
  you are using the 3 numbers of the volume formula
  (length x width x height) 6 m x 2m x 4m 48m3

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Lab Measurement Instruments

• A meter stick is used to find length
• A balance is used to find mass.
• A scale is used to find weight.
• A graduated cylinder is used to find volume.
• The bottom of the curve of the graduated cylinder
  is called the meniscus.
• Liquids are heated in a flask using tongs.

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Volume of a Irregular-Shaped Object

• If you have an object that you cannot measure
  with a meter stick (such as a rock), you would
• 1) Fill a cylinder with water and measure from
  the meniscus
• 2) Put in the rock and measure the meniscus
• 3) Find the difference ( in mL)

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How Mass and Volume Affect Density
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Density

• Density This is a physical property -
  thickness of matter. It is the amount of mass
  per unit of volume. Formula mass divided by
  volume m/v
• Example an object that has a mass of 28g and a
  volume of 7
• 28 g
  28g
• 7 ml 4 g/ ml OR 7 cm3 4g/
  cm3
• Question Does a larger object always have
  greater density? Which has a greater density, a
  baseball or a beach ball?
• WHEN YOU HAVE GREATER MASS COMPARED TO A SMALLER
  VOLUME, THE HIGHER THE DENSITY.
• Rate is a ratio between 2 different types of
  measurement. For example density is a ratio
  between mass and volume.

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How the Titanic Sank
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Density is a Physical Property
Every element on the periodic table can be
identified by a special physical property. Every
element has its own specific density. In other
words, it doesnt matter how large or small the
sample is, each element would have a specific
density. So, if you wanted to identify an
element, what are the two things you could find
out about it that would prove what the element
is?
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SI Temperature

• Temperature In SI, Celsius is normally used
  instead of Fahrenheit
• Conversion oC (oF-32)
• 1.8
• Freezing Point (water) 0 oC
• Boiling Point (water) 100 oC
• For extreme temperatures we use Kelvin
• K oC 273
• Absolute zero -273.15 oC or 0 K (no heat at
  all) Kelvin does not use a degree mark.

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Temperature

• Kelvin is different from Fahrenheit and Celcius
  in that it does not use a degree superscript (o).
  To remember Kelvin, think of the magic Kelvin
  number 273. Differences between Fahrenheit,
  Celcius and Kelvin

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Absolute Zero

• Absolute Zero is the temperature in which there
  is no molecular movement, because there is
  absolutely no heat energy. Absolute Zero is as
  cold as it gets.
• Theoretically, Absolute Zero is achieved at 0 K
  (or -273o C.) It does not occur naturally, but
  there have been severa
• l attempts to achieve it in a lab setting
• http//www.youtube.com/watch?vK1ZWN1rqTX4

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Metric System Prefixes (Memorize These!)

• In the metric system, the prefixes of units
  (meters, grams and liters) indicate if you are
  dealing with whole units (a e), or fractions of
  one unit (f I)
• a. mega- (M) 1 000 000 x
• b. kilo- (k) 1 000 x
• c. hecto- (h) 100 x
• d. deka- (da) 10 x
• e. Main Unit 1 x (meter, gram, liter)
• f. deci- (d) 0.1 x (1/10)
• g. centi- (c) 0.01 x (1/100)
• h. milli- (m) 0.001 x (1/1000)
• i. micro- (u) 0.000 000 001 x

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Metric System Conversion

• How do you convert from one unit to another?
• First, they must be related. For example, you
  can convert inches to feet or yards, but can you
  convert inches to pints or quarts?
• It is the same with metrics. You can convert
  meters to meters, grams to grams, or liters to
  liters (or cm3), but you cant convert meters to
  grams or liters.

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Metric Conversion

• 0.050 cm to _____ m
• (1/500 of a centimeter how many meters?)
• Step 1 Convert larger unit to the smaller units
  (how many centi are in a meter?) 100
• 0.050 divided by 100 0.0005
• 0.050 cm . 0005 meters

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Metric Conversion Steps

• 1) Which unit is the smallest?
• 2) How many of that small unit can go into one of
  the large units? Write that down, because the
  of 0s is how many places you are moving.
• 3) If the you looking at a fraction (small units
  into large), move the decimal to the left
• 4) If you are looking at multiple units (large
  into small), move the decimal to the right.

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Metric Conversion

• Look again 0.050 cm ? m
• 0.050 divided by 100 0.0005
• Answer 0.00050 m
• Get rid of the first and last 0 (no value)
• Answer .0005 m
• Did you notice that, because the metric system is
  based on 10, you really only had to move the
  decimal place? You dont have to actually divide!

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Metric Conversion

• When you divide or multiply by
• 1000, move the decimal 3 places
• 100, move the decimal 2 places
• 10, move the decimal 1 place
• If you are going from a small unit to a larger
  unit (i.e. centi to a whole meter) move the
  decimal to the left
• If you are going from a larger unit to a smaller
  unit (i.e. meter to centi) move the decimal to
  the right