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Chemistry

Chemistry. Study of matter and the changes it undergoes. Measuring and Calculating. SI System Qualitative vs Quantitative Qual – describes a property w/o measuring it Quant – measurement with a #. Metric System. Prefixes – Kilo hecta deka base deci centi milli

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Chemistry

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  1. Chemistry Study of matter and the changes it undergoes

  2. Measuring and Calculating • SI System • Qualitative vs Quantitative • Qual – describes a property w/o measuring it • Quant – measurement with a #

  3. Metric System • Prefixes – Kilo hecta deka base deci centi milli System is based on the power of 10

  4. Important Measurements • Mass – measures quantity of matter • Base unit (kg) • Weight – measures force of gravity between 2 objects (earth and object being weighed)

  5. Base Units Length – m Time – s Mass – kg Temperature - K

  6. Accuracy vs. Precision Accuracy – how close a measurement is to the true or accepted value Precision – how close a set of measurements are to EACH OTHER ****Think dart board!!!

  7. Significant Figures • Digits that occupy places for which an actual measurement was made • Includes one uncertain or estimated digit • # of sig figs depends on the instrument doing the measuring!!!

  8. Sig Fig Rules • Digits other than zero are always significant 96g 61.4g 3253.854 cm

  9. Sig Fig Rules 2) One or more final zeros used after the decimal are always significant 4.72 km 4.72000 cm

  10. Sig Fig Rules 3) Zeros between 2 other sig figs are always significant 5.029 m 306 km

  11. Sig Fig Rules 4) Zeros as placeholders are not significant 7000 g 0.000783 g

  12. Calculating with Sig Figs • What happens to the # of sig figs when we add or multiply #’s???? Ex: length = 2.02 cm Width = 1.63 cm Height = 3.2 cm V = l x w h V = 10.53632 cm 3 ** Do we really need all these decimal places???

  13. Multiplying and Dividing • Multiplying or dividing - # of sig figs is the same as the measurement having the least # of sig figs • So in the above example answer would be = 10.8 cm 3 Ex: Area = l x w l = 1.1 cm w = 2.38 cm A = l x w = 2.38 x 2.618 A =

  14. Adding or Subtracting • Round the answer so that it has the same # of decimal places as the measurement having the least # of decimal places Ex: 5.43 cm 2.6 cm + 1.57 cm 9.60 cm = 9.6 cm

  15. Density • Mass per unit volume D = m V Units = g/ml OR g/cm 3

  16. Percent Error % Error = accepted value – experimental value x 100 accepted value

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