Ch' 2 Scientific Method

1
Ch. 2 Scientific Method

• A systematic approach to solve problems through
  investigations by 1. Observing, 2. Generalizing,
  3. Theorizing, 4. Testing, 5. Conclusion.
• Whats done in an observation
• Collect data, communicate
• Generalizing
• Organize data, hypothesis
• Theorizing
• Planning and predicting

2

• Test
• Design experiment, test, graph and interpret
  results
• Conclusion
• May change hypothesis and retest
• Explain what happened in your results

3
Measurements

• Why do we need measurements?
• If I told you to go get me a pop would you know
  what size?
• The International System of Units (SI) is used
  throughout the world so we dont confuse figures
  and measurements.
• SI is metric
• Written the following way 21 400 or 0.157 82
• 7 SI fundamental units ? Mass, time, temperature,
  length, amount of substance. Pg. 34

4
SI Unit Prefixes

• Unit of measurements for length
• KHDMDCM
• Kilo, hecto, deka, meter, deci, centi, milli
• Ex. Kilogram (1000 grams) or Kilometer (1000
  meters)
• 1 gram is about 1 pencil mass
• Your book is about 2 Kg
• Derived Unit are combinations of fundament al
  units.

5
Derived Units

• Area ? length X width (m2)
• Volume ? length X width X height (m3)
• Volume is the amount of space occupied by an
  object.
• 1ml 1cm3
• 1 liter 1000-ml
• 1 ml how many liters?
• Density is mass divided by volume (Dm/v)
• How heavy something is for its size.
• Ex. Pg. 38 (Density Lab)

6

• Temperature is the measure of the average kinetic
  energy of the particles in a sample of matter.
• What is the SI unit for temp.?
• Kelvin (K)
• Heat is the sum of the kinetic energy of the
  particles in a sample of matter.
• How does a thermometer work?
• We use Celsius more than Kelvin
• 0 C 273 K freezing point
• 100 C 373 K- boiling point

7

• Joule is force times length (f X l)
• 1 J 1 n-m
• Joule is the SI unit for energy
• A calorie is the amount of heat needed to raise
  the temperature of 1 g of water 1 degrees C.
• 1 calorie 4.184 J
• Kcal or C KJ
• Food Calories are kilocalories.
• Conversion Factors Sample Problem 2-2

8

• Specific heat is the amount of heat energy
  required to raise the temp. of 1 g of a substance
  1 degree C.
• Label is J/g x C
• Water heats up and cools down slowly, thus it has
  a high specific heat.
• Accuracy vs. Precision
• Precision is determined by how close your results
  are to each other.
• Accuracy is determined by how close your results
  are to the correct answer.
• Ex. Dart Board

9
SIGNIFICANT FIGURES

• Significant figures are all the digits known with
  certainty plus one final digit, which is
  uncertain or estimated.
• Read pg. 46 bottom 2 paragraphs
• Read pg. 47 Table 2-5
• Do Sample Problems on pg. 47 48
• Rounding off Addition Subtraction Problems
• Rounding off Multiplication Division Problems

10
Scientific Notation

• This is very helpful to determine the correct
  number of significant figures.
• Ex. 50 890 ? 5.089 X 104
• Ex. 0.005031 ? 5.031 X 10-3
• Ex. 74 621 000 ? 7.462 1 X 107
• Using Adding Subtracting Scientific Notation
• Using Multiplying Dividing Scientific Notation