1 / 27

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!!!

jensen
Download Presentation

Catalyst 9/19/12

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related