1. Measurement & Calculations Chapter 2

2. The Scientific Method 1. Observing 2. Formulating hypothesis 3. Testing 4. Theorizing 5. Publish results

3. Definitions Data may be descriptive (qualitative) or numerical (quantitative). Data may be descriptive (qualitative) or numerical (quantitative). System- a specific portion of matter in a given region of space that has been selected for study during an experiment System- a specific portion of matter in a given region of space that has been selected for study during an experiment Hypothesis- a testable statement gathered from observing data Hypothesis- a testable statement gathered from observing data Theory- a broad generalization that explains a body of facts Theory- a broad generalization that explains a body of facts

4. SI Measurement SI- System International SI- System International QuantitySymbol Unit name Abbreviation LengthlMeterm MassmKilogramkg TimetSeconds Temper-atureTKelvinK Amount of substance nMolemol

5. Derived Units Combinations of SI base units form derived units. Combinations of SI base units form derived units. Volume- Amount of space occupied by an object Volume- Amount of space occupied by an object volume= length x width x height volume= length x width x height Density- The ratio of mass to volume Density- The ratio of mass to volume D= mass_ D= mass_ volume volume

6. Problem A sample of aluminum metal has a mass of 8.4 grams. The volume of the sample is 3.1 cm 3. Calculate the density of aluminum.

7. Conversion Factors English conversions 1 gallon= 3.79 liters 1 kilogram= 2.2 pounds 1 inch= 2.54 centimeters 1 quart= 0.95 liters 1 meter= 39.37 inches 1 mile= 1608 meters= 5280 feet 1 mole= 6.02x10 23 molecules= 22.4 liters

8. Conversion Factors M- mega (1000000) k- kilo (1000)DR. UL: h- hecta (100)If you move da- deca (10)down the chart, b- base (1)decimal moves to d- deci (.1)the right; up the c- centi (.01)chart, decimal m- milli (.001)moves to the left! μ- micro (.000001)

9. Using Scientific Measurements Accuracy- measured values are close to the accepted value Accuracy- measured values are close to the accepted value Precision- measured values are close to one another, but not necessarily close to the accepted value Precision- measured values are close to one another, but not necessarily close to the accepted value

10. Percent Error Accuracy can be compared with the accepted value by using percent error Accuracy can be compared with the accepted value by using percent error Percent error= Accepted value- Experimental value x 100 Percent error= Accepted value- Experimental value x 100 Accepted value Accepted value

11. Problem A student measures the mass & volume of a substance & calculates its density as 1.40 g/mL. The correct, or accepted, value of the density is 1.36 g/mL. What is the percent error?

12. Error in Measurement Some uncertainty always exists in any measurement Some uncertainty always exists in any measurement Factors affecting the measurement are: Factors affecting the measurement are: The skill of the measurer The skill of the measurer The conditions of the measurement The conditions of the measurement The measuring instruments The measuring instruments

13. Rules for significant figures 1. Zeros between nonzeros are significant. 40.7  3 S.F. 40.7  3 S.F. 2. Zeros in front of nonzeros are not significant. 0.0009  1 S.F. 0.0009  1 S.F. 3. Zeros at the end of a number & to the right of a decimal are significant. 47.00  4 S.F. 47.00  4 S.F.

14. Rules con’t… 4. Zeros at the end of a number without a decimal are not significant. 2000  1 S.F. 2000  1 S.F. 5. A decimal placed after the zeros indicates that they are significant. 2000.  4 S.F. 2000.  4 S.F.

15. Problem How many significant figures are in each of the following measurements? a) 28.6 g b) 3440. cm c) 910 m d) 0.04604 L e) 0.0067000 kg

16. Scientific Notation Shorthand method of writing very large & very small numbers Shorthand method of writing very large & very small numbers Takes the form M x 10 n Takes the form M x 10 n M is greater or equal to 1 but less than 10 M is greater or equal to 1 but less than 10 n is a whole number & is determined by the number of places that the decimal was moved to get M n is a whole number & is determined by the number of places that the decimal was moved to get M If decimal is moved to left, n is (+) If decimal is moved to left, n is (+) If decimal is moved to right, n is (-) If decimal is moved to right, n is (-) 450000 = 4.5 x 10 5 450000 = 4.5 x 10 5

17. Problem Convert each of the following to scientific notation form: a) 0.000379 b) 25000000 c) 600000000000 d) 0.0000041