The Nature of Science

1
The Nature of Science

• How do people gather scientific information?

2
Scientific Method

• IM TAD
• Identify a Problem
• Make a Hypothesis
• Test the Hypothesis (Perform an Experiment)
• Analyze the Data
• Draw Conclusions
• Sometimes a 6th step is included in which you
  share your conclusions with others

3
Hypothesis vs. Theory vs. Law

• Hypothesis An educated guess
• Scientific Theory A hypothesis supported by
  many experiments
• Scientific Law - facts of nature accepted as truth

4
Controlled Experiments

• A Controlled Experment is one where only one
  variable is tested at a time
• Why is it important to use controlled experiments?

5
Controlled Experiments

• Control Group the group that doesnt receive
  the experimental treatment, a standard for
  comparison
• Independent Variable the variable in the
  experiment you change
• Dependent Variable the variable in the
  experiment that only changes because you changed
  the independent variable

6
Controlled Experiments

• Example
• Merck decides to test a new antibiotic to see if
  it will cure patients sinus infections. Some
  testers are given pills containing the new
  antibiotic and others are given a placebo, or
  sugar pill.
• Identify
• Control
• Independent Variable
• Dependent Variable

7
The Metric System

• In the US, we use the English system of units
  (lbs, in., oz., etc.)
• The rest of the world, including the scientific
  world, uses the SI (Systeme Internationale) or
  Metric System
• Why?
• Its universal (used everywhere but US)
• Units are converted based on factors of 10

8
SI Units

• What are the SI base units for these
  measurements?
• Length/distance?
• Meter (m)
• Volume?
• Liter (L)
• Time?
• Seconds (s)

9
SI Units

• What are the SI base units for these
  measurements?
• Temperature?
• Kelvin (K), the absolute scale for Celsius (C)
• Mass?
• Grams (g)?
• We use grams for the base unit, but kilograms
  (kg) are considered the SI unit for mass

10
Metric Conversions

• We use SI units because its easy to convert
  between magnitudes
• We use a prefix to identify the magnitude of the
  measurement
• Examples kg, cm, mL
• To remember the prefixes, use the mnemonic
• King Henry Died by Drinking Chocolate Milk

11
Metric Prefixes
Prefix Symbol Magnitude
Kilo k 1,000(103)
Hecto h 100 (102)
Deca da 10 (101)
base unit g, L, m 1 (100)
Deci d 0.1 (10-1)
Centi c 0.01 (10-2)
Milli m 0.001 (10-3)
12
Converting between Metric Units

• To convert between metric units, count how many
  spaces are between the units
• Move the decimal point that many spaces in the
  direction you counted towards
• Example 1 10m ? cm
• Answer 1,000cm
• Example 2 10mL ? hL
• Answer 0.0001hL

kilo hecto deca base deci centi milli
13
Density

• The amount of matter in a given amount of space
  is known as Density(D)
• D m/V
• Common units g/mL, g/cm3
• Note 1mL 1cm3
• Example If a 45.2g block has a volume of 11.6mL,
  what is its density?
• D 45.2g/11.6mL
• D 3.90g/mL

14
Area

• A l x w
• For a square A side2
• For a triangle A ½ bh
• Common units cm2, m2
• Example If a square has a length of 5cm and a
  width of 3cm, what is its area?
• A 5cm x 3cm
• A 15cm2

15
Matter, Mass and Weight

• Matter anything with mass and volume
• Mass the amount of matter in an object
• Weight the effect of gravity on an object
• What is the difference between mass and weight?
• Gravity