Chemistry I Pre Ap

Chemistry I Pre AP

Mr. Hames 6th Hour Chapter 2 Measurements and Calculations Section 1- Scientific Method  Logical Problem Solving Approach 1. Observe And Collect Data 2. Form and Hypothesise 3. Test Hypothesis by doing experiments 4. Form Theories by ecperimental data Either prove hypothesis or modify and re-experiement. Section 2 – Unit Measurements  Measurements – Number and a unit Ex.10.0 mL  Quantity – Volume  S.I. system – 7 base ubites  S.I. Derived units  by multiplying or dividing base units

• Area = L X W= m. X m. = m2 (squared) • Volume = L W H = m m m = m3(cubed) • Velocity= D/T (distance/time) = m/m X

X

X

X

 Non – S.I. units =cm3 = dm 3  Temp – c◦  Density = mass/volume – Kg/m3(cubed) Dimensional Analysis  We use Conversion factors to change on unito to another making sure the units cancel properly to give us our desired units. Acuracy Vs. Precision  “ Acuracy” refers to the closeness of a result to the accepted book Value ( how close you are to the bull’s eye). “Precision” refers to how well you reproduce your results. Are your results close to each other? Percentage of error  This tells you how accurate your results are. The smaller the percentage of error the the more accurate you are.  % error = experimental value – accepted value/accepted value X 100 Uncertainty in Lab Meaurements  All Lab measurements have inherent uncertainty also you as an observer have uncertainty in reading and instrument ( see Figure 4 page 46) 6.36 +/- 0.01 6(certain).3(certain)6(uncertain) Significant Figures  In a measurement this includes all certain digits + the first uncertain digit. In the case above 6.36 cm has 3 significan Figures.

Note no practice problems in type notes.