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Catalyst 9/19/12

Catalyst 9/19/12. Welcome Back! This week all rules/procedures are now in place, which means you should all be wearing your IDS ! In your notes, write down 3 class rules you remember from last week. Pick up your honors books!!! BINDERS and FOLDER DUE TOMORROW!!!

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Catalyst 9/19/12

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  1. Catalyst 9/19/12 • Welcome Back! This week all rules/procedures are now in place, which means you should all be wearing your IDS! • In your notes, write down 3 class rules you remember from last week. • Pick up your honors books!!! • BINDERS and FOLDER DUE TOMORROW!!! • Turnitin.com DUE FRIDAY (see website) • Class Dojo is in effect  (participate!)

  2. 9/17-9/21 Week 2 HW

  3. Scientific Notation, SI Units, and Significant Figures

  4. Scientific Notation Why is scientific notation useful in science? - Many measurements in science are very large or very small numbers. Scientific notation expresses these numbers as a product of a number between 1 and 10 and a power of ten. • Decimal placement …move the decimal point until you have a number between 1 and 10 623  6.23 x 10??? 2. Exponent …how many times do you have to multiply the new number by 10 to get the original number? 623 = 6.23 x 10 x 10 = 6.23 x 102

  5. Scientific Notation 2. Exponent …multiplying by 10 is the same as moving the decimal point! Think of scientific notation as a condensed representation of a number. The exponent tells you how many places and in which direction you need to move the decimal place to get the original number. 420000. = 4.2 x 105 0.000715 = 7.15 x 10-4 *REMEMBER LIP! Left Is Positive 5 4 3 2 1 1 2 3 4

  6. Scientific Notation Which one is the bigger number? • 3,520 • 2.1 x 104 A) 0.065 B) 9.8 x 10-5 B! 2.1 x 104 = 21,000 A! 9.8 x 10-5 = 0.000098

  7. Scientific Notation A few more examples… 800 = 8 x 10 x 10 = 8 x 102 2531 = 2.531 x 10 x 10 x 10 = 2.531 x 103 0.0014 = 1.4 ÷ 10 ÷ 10 ÷ 10 = 1.4 x 10-3 Decimal after the first non-zero digit!

  8. Scientific Notation Practice: Convert back toan ordinary number 1.87 x 10–5 = 3.7 x 108 = 7.88 x 101 = 2.164 x 10–2 = 0.0000187 370,000,000 78.8 0.02164

  9. Convert to Scientific Notation: 12,340 = 0.369 = 0.008 = 1,000,000,000 = 1.234 x 104 3.69 x 10–1 8. x 10–3 1. x 109

  10. No Cussing! The following 4-Letter words are forbidden here: Inch Mile Foot Pint Yard Acre And we never swear the BIG F (useoC) Please keep it clean and Metric

  11. SI System • The International System of Units • Derived Units Commonly Used in Chemistry Map of the world where red represents countries whichdo not use the metric system

  12. The International System of Units Quantity Name Symbol • Length meter m • Mass kilogram kg • Time second s • Amount of substance mole mol • Temperature Kelvin K • Electric current amperes amps • Luminous intensity candela cd Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 16

  13. SI Unit Prefixes

  14. Certain Digits Estimated Digit Significant figures • Method used to express accuracy and precision. • You can’t report numbers better than the method used to measure them. • 67.20 cm = four significant figures ???

  15. Significant figures • The number of significant digits is independent of the decimal point. • 255 • 31.7 • 5.60 • 0.934 • 0.0150 These numbers All have three significant figures!

  16. Significant figures • Zeros are what will give you a headache! • They are used/misused all of the time. • SEE p.24 in your book!

  17. 4,008 - four significant figures 0.421 - three significant figures Leading zero Captive zeros 114.20 - five significant figures Trailing zero Rules for zeros ??? • Leading zeros are notsignificant. • Captive zeros are always significant! ??? Trailing zeros are significant … IF there’s a decimal point! ???

  18. Examples • 250 mg • \__ 2 significant figures • 120. miles • \__ 3 significant figures • 0.00230 kg • \__ 3 significant figures • 23,600.01 s • \__ 7 significant figures

  19. Significant figures:Rules for zeros • Scientific notation - can be used to clearly express significant figures. • A properly written number in scientific notation always has the proper number of significant figures. 0.00321 = 3.21x 10-3 Three Significant Figures

  20. Significant figures and calculations • An answer can’t have more significant figures than the quantities used to produce it. • Example • How fast did you run if you • went 1.0 km in 3.0 minutes? 0.333333 speed = 1.0 km 3.0 min = 0.33 km min

  21. ONLY 3 SIG FIGS! ONLY 2 SIG FIGS! Significant figures and calculations • Multiplication and division. • Your answer should have the same number of sig figs as the quantity in the calculation with the smallest number of significant figures. 21.4 cm x 3.095768 cm = 66.2 cm2 135 km ÷ 2.0 hr = 68 km/hr

  22. 123.45987 g + 234.11 g 357.57 g 805.4 g - 721.67912 g 83.7 g Significant figures and calculations • Addition and subtraction • Your answer should have the same number of digits to the right of the decimal point as the number having the fewest to start with.

  23. Rounding off numbers • After calculations, you may need to round off. • If the first insignificant digit is 5 or more, you round up • If the first insignificant digit is 4 or less, you round down.

  24. Examples of rounding off If a set of calculations gave you the following numbers and you knew each was supposed to have four significant figures then - 2.5795035 becomes 2.580 34.204221 becomes 34.20 1st insignificant digit

  25. 5. • Rewrite each of the following as an ordinary number • a. 4.31 x 10-2 • b. 9.54 x 103 • c. 3.79 x 10-5 • d. 7.19 x 102 0.0431 9540 0.0000379 719

  26. 8. • What will the exponent for the power of 10 be when each of the following numbers is written in scientific notation? • 3981.2 • 0.0004521 • 453.9 • 0.994 x 102 3 -4 2 1

  27. Catalyst 9/20/12 Take out your class materials: 1 Binder 5 Dividers (Class Notes, Daily Hwk, Handouts/Labs, Quizzes/Tests, Reference 2 pocket folder Scientific Calculator Take out your homework and stamp sheet! In your class notes section, answer the following questions: Which is smaller, 1 x 10-7 or 1 x 10-3 Which is larger, 2.3 x 103 or 1.8 x 106

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