Scientific Method

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Scientific Method

• A method by which natural phenomena are explained

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How would you describe thunder lightning?
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A mythological being?
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A dream?
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Or science?
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Scientific MethodRules of the Game

• 1. One assumption the phenomena to be
  described are able to be described by natural
  phenomena.

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Steps of the Scientific Method

• 1. Make observations on something interesting
• 2. Form a hypothesis, an educated guess
• 3. Perform experiments to disprove the
  hypothesis
• 4. Reevaluate the hypothesis

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Conducting an Experiment

• Control group
• a group in an experimental study that receives no
  special treatment

• Experimental group
• a group receiving special treatment in an
  experimental study

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So whats the difference between these two groups
anyway?

• Independent variable
• a variable that is manipulated or modified in an
  experiment
• CAUSE

• Dependent variable
• a variable in an experimental study that may
  change as a result of the manipulation of the
  independent variable
• EFFECT

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Weve got to do what? Graph it?!?!

• Independent variable
• x axis

• Dependent variable
• y axis

Y
X
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Once the reevaluation is over . .

• Theory a tested explanation of natural
  phenomena
• Law a concise statement or mathematical
  equation about a relationship, i.e. Emc2

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Qualitative versus Quantitative
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How would you describe this picture?
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Possible ways to describe it

• Number of people
• Number of decorations
• Number of lights

• Appearance of people
• Type of decorations
• Type of wall coverings

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What does this mean?

• Quantitative
• a physical description involving the numbers of a
  situation

• Qualitative
• a physical description involving the physical
  appearance of a situation

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While it may seem that these two are opposite,
they are really the halves of the whole
description.
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Application to a Candle

• What types of observations can we make about a
  candle? How about in order to describe how a
  candle is able to keep a flame and give off light?

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Candle Activity
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The Metric System
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History

• Early measurements reflected the size of the king
  or queen of the land

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• The problem was that as the kings size changed
  so did the basis for measurement

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• In 1670, Gabriel Mouton devised a system of
  measurement based upon standards instead of the
  kings features

• The Metric System

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Metric vs. English

• easier to use since nonexact measurements are
  expressed as decimals, not fractions
• easier to use since conversions are all based
  upon powers of 10

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Metric Base Units
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Metric Prefixes (Greater than)
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Metric Prefixes (Less Than)
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So how do we use this?

• 1000 g 1 kg
• 100 m 1 hm
• .01 m 1 cm
• .001m 1 mm

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Metcetera (Wet to Dry Volume)

• 1.0 cm3 1.0 mL
• 1.0 dm3 1.0 L

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Conversions

• Bigger Base Unit Smaller
• k, h, da m, l, g d, c, m

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Convert

• 5 dm to cm
• 5 mm to cm

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• 5 km to dam
• 5 hm to km

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2 step conversions

• 5 km to mm
• 4 cm to dam

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Measurement Lab

• Station 1 Using a ruler
• Never measure from the end

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Measurement Lab

• Station 2 Using a graduated cylinder
• Meniscus the curved line of liquid that is read
  for measurement in certain types of glassware

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Measurement Lab

• Station 3 The Pipette
• Using a known piece of glassware to calibrate an
  unknown piece of glassware

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Measurement Lab

• Station 4 Using different types of pipettes
• Mohr and Volumetric

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Measurement Lab

• Station 5 Using the buret
• Only glassware that is graduated upside down

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Measurement Lab

• Station 6 Using a thermometer

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Measurement Lab

• Station 7 Using a balance
• How many digits do you write down?

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Measurement Lab

• Station 8 Using a barometer
• Used to measure pressue
• Units mm Hg

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Scientific Notation

• Shorthand way of writing numbers without having
  to use placeholder zeros
• 1,000,000 1 x 106
• 0.005 5 x 10-3

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Scientific Notation

• Rules
• The number in front of the decimal must be
  between 1 and 9.
• In order to get only one number in front of the
  decimal you will need to move the decimal
• If you move to the right, the exponent is
  negative
• If you move to the left, the exponent is positive

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Write these in scientific notation

• 0.00345
• 1,002,000,000
• 0.34
• 403

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Write these in standard notation

• 2 x 10-2
• 3 x 104
• 5.67 x 10-3
• 4.56 x 102

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Significant Digits

• Numbers (digits) that show the degree of accuracy
  and precision of a measurement
• Accuracy How close a measurement is to the
  accepted value
• Precision Repeatability of a set of
  measurements to be similar in value

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Atlantic-Pacific Rule

• Atlantic
• If the decimal is absent, start counting from the
  right (Atlantic Ocean) side with the first
  nonzero. Once you start counting keep on
  counting.
• 2040

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Atlantic-Pacific Rule

• Pacific
• If the decimal is present, start counting from
  the left (Pacific Ocean) side with the first
  nonzero. Once you start counting keep on
  counting.
• 0.034500

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How many significant digits are in these numbers?

• 2,339,009
• 0.00987
• 0.005600
• 203040

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Math with Significant Digits

• When you add and subtract simply line up the
  decimals and keep the fewest places after the
  decimal in your answer.
• 234.0098 3.01 ?
• 234.0098 30.0 ?

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Math with Significant Digits

• When you multiply and divide, your answer should
  have the fewest digits shown in the original
  numbers.
• 2.2 x 3 ?
• 2.100 / 7.0 ?

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Density

• A ratio of a substances mass to its volume
• A constant value for a given substance no matter
  how much mass or volume
• D m/v
• Units are a combination of mass and volume, ex.
  g/mL or kg/L

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• A rock with a mass of 25.0 g has a volume of 5.0
  mL, as determined by water displacement. What is
  the density of the rock?

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• A wooden block with measurements of 2 cm, 3.0 cm,
  and 0.5 cm has a mass of 9.00 mg, what is the
  density of the wooden block?

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Density Gradient Practical