Ch. 2 - Scientific Method

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

Test Design experiment, test, graph and interpret results Conclusion May change hypothesis and retest Explain what happened in your results Why Measurements 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 Unit SI Unit Prefixes 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 fundamental units. Area Derived Units 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 (D=m/v) How heavy something is for its size. Ex. Pg. 38 (Density Lab) 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 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 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 Accuracy is determined by how close your results are to the correct answer.

Precision is determined by how close your results are to each other. Ex. Dart Board pg. 44 Sample Problem 2-3 (Percent Error) 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 This Scientific Notation 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