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Chapter 1

Chemical Foundations. Chapter 1. Chemistry. t he study of matter and the changes it undergoes. sodium chloride. chlorine. sodium. Scientific Method. Benzene Ring. Make observations Formulate hypotheses Perform experiments. Units of Measurements in SI Units. Prefixes.

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Chapter 1

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  1. Chemical Foundations Chapter 1

  2. Chemistry • the study of matter and the changes it undergoes sodium chloride chlorine sodium

  3. Scientific Method Benzene Ring • Make observations • Formulate hypotheses • Perform experiments

  4. Units of Measurements in SI Units

  5. Prefixes

  6. How to use prefixes • Convert 500.0 mg to grams.

  7. How to use prefixes • Convert 700. nm to meters.

  8. How to use prefixes • Convert 8905 grams to kilograms.

  9. Uncertainty in Measurement • 20.15 mL • 20.14 mL • 20.16 mL • 20.17 mL • 20.16 mL uncertain digit certain digits

  10. Significant figures automatically indicate the uncertainty in a measurement. 20.15 mL 4 significant figures The last digit is usually assumes to be

  11. Another way to write uncertainty

  12. All measurements have some degree of uncertainty!

  13. QUESTION • In analyzing a soil sample, a soil scientist measures 15.00 g sample. Later the scientist uses a scale which measures 15 g. • What is the difference between the measurements 15.00 g and 15 g?

  14. ANSWER • 15.00 g • Means • Measurement is between 14.99 g and 15.01 g. • 15 g • Means • Measurement is between 14 g and 16 g

  15. Precision & Accuracy • Not precise • Not accurate

  16. Precision & Accuracy • Precise • Not accurate

  17. Precision & Accuracy • Precise & accurate!

  18. Precise Measurements • 20.15 mL • 20.14 mL • 20.16 mL • 20.17 mL • 20.16 mL

  19. Accuracy • The agreement of a particular value with the true value. Precision • The degree of agreement among several measurements of the same quantity

  20. Significant Figure Review • Nonzero integers always count as sig figs. 1465 893 21

  21. Sig Fig Review • Leading Zeros Zeros that precede nonzero digits do not count as sig figs. 0.0034 0.89 0.00255

  22. Sig Fig Review • Captive Zeros Zeros that are between nonzero digits always count as sig figs 1.005 409 2004

  23. Sig Fig Review • Trailing Zeros Zeros at the right end of a number are significant if there is a decimal present. 100.0 20 4000 1.00 x 102

  24. Atlantic Pacific Rule Pacific Ocean Decimal is Present Count sig figs from left 1.00 0.50050 Atlantic Ocean Decimal is Absent Count sig figs from right 100 50050

  25. Sig Fig Review • Exact Numbers If a measuring device was not used, then the number is an exact number. Counting: 10 apples Defined Quantities: 1 inch = 2.54 cm Numbers in Formulas: 2πr (The 2)

  26. Sig Figs & Calculations • Multiplication & Division Round to the least precise measurement used in the calculation. 4.88 x 1.5 = 7.32 7.3

  27. Sig Figs & Calculations • Addition & Subtraction The result has the same number of decimal places as the least precise measuremnt. 12. 00 + 6.001 = 18.001 18.00

  28. Rules for Rounding • In a series of calculations, carry the extra digits through to the final result, then round.

  29. Rules for Rounding • When you round, • if the digit to the right of the final sig fig is less than 5, then the preceding digit stays the same. 6.22 6.2 • If the digits is equal to or greater than 5, then the preceding digit should be increased by 1. 4.57 4.6

  30. Dimensional Analysisor Units Rock

  31. Unit Conversions A glass rod is 6.00 inches long. What is the length in centimeters? Unit Factor

  32. Temperature

  33. Density – a derived unit

  34. Units for Density g/cm3 g cm-3 g/L

  35. Classification of Matter Matter Heterogeneous Mixtures Homogeneous Mixtures Pure substances Compounds Elements Atoms Electrons Nucleus protons neutrons quarks quarks

  36. States of Matter Solid • Definite shape & volume • particles vibrate around fixed positions

  37. Liquid • Take the shape of the container • Definite volume • Particles are free to move

  38. Gas • No definite shape • No definite volume

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