catalyst 9/19/12
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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!!! - PowerPoint PPT PresentationTRANSCRIPT
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!)
9/17-9/21 Week 2 HWASSIGNED DUE
Wed. 9/19 Book Problems: Ch2: Questions and Problems: 1, 5, 6, 8, 13abcefg. TURNITIN.COM DUE FRIDAY!
Signed Forms
Thurs. 9/20 Problem Set due next Monday! Binder, Book Problems, Turnitin.com
Fri. 9/21 Density Column Extra Credit, work on problem Set, Study for QUIZ Tuesday!
None
Mon. 9/24 Finish Density Blocks Lab, Study for Ch.2 Quiz tomorrow!
None
Tues. 9/25 Chris Jordan Turnitin.com Density Blocks Lab, Quiz TODAY
Scientific Notation, SI Units, and
Significant Figures
Scientific NotationWhy 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.
1. 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
Scientific Notation2. 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
5 4 3 2 1
1 2 3 4
*REMEMBER LIP!Left Is Positive
Scientific Notation
Which one is the bigger number?A) 3,520B) 2.1 x 104
A) 0.065B) 9.8 x 10-5
B! 2.1 x 104 = 21,000
A! 9.8 x 10-5 = 0.000098
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!
Scientific Notation Practice: Convert back to an 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
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
No Cussing!The following 4-Letter
words are forbidden here:
Inch MileFoot PintYard Acre
And we never swear the BIG F (useoC)
Please keep it clean andMetric
SI System• The International System of Units• Derived Units Commonly Used in Chemistry
Map of the world where red represents countries which do not use the metric system
The International System of Units
• Lengthmeter m• Mass kilogram kg• Time second s• Amount of substance mole mol• Temperature Kelvin K• Electric current amperes amps• Luminous intensity candela cd
Quantity Name Symbol
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 16
SI Unit PrefixesPrefix Symbol Meaning Power of 10mega- M 1,000,000 106
kilo- k 1,000 103
hecto- h 100 102
deca- da 10 101
----- ----- 1 100
deci- d 0.1 10-1
centi- c 0.01 10-2
milli- m 0.001 10-3
micro- 0.000001 10-6
nano- n 0.000000001 10-9
Significant figuresMethod 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
EstimatedDigit
Certain Digits
???
Significant figuresThe number of significant
digits is independent of the decimal point.
255 31.7 5.60 0.934
0.0150
These numbersAll have three
significant figures!
Significant figures
Zeros are what will give you a headache!
They are used/misused all of the time.
SEE p.24 in your book!
Rules for zerosLeading zeros are not significant.
Captive zeros are always significant!
0.421 - three significant figuresLeading zero
Trailing zeros are significant …IF there’s a decimal point!
114.20 - five significant figuresTrailing zero
???
???
4,008 - four significant figuresCaptive zeros
???
Examples
250 mg \__ 2 significant figures 120. miles \__ 3 significant figures 0.00230 kg \__ 3 significant figures 23,600.01 s \__ 7 significant figures
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 = 3.21 x 10-3
Three SignificantFigures
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 youwent 1.0 km in 3.0 minutes?
speed = 1.0 km 3.0 min
= 0.33 km min
+-1
/x
02 3
4 5 67 8 9
.
CE
EE
log
ln
1/x
x2
cos tan
0.333333
Significant figures and calculationsMultiplication 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
ONLY 3 SIG FIGS!
ONLY 2 SIG FIGS!
Significant figures and calculationsAddition and subtractionYour answer should have the same number of digits to the right of the decimal point as the number having the fewest to start with.
123.45987 g+ 234.11 g 357.57 g
805.4 g- 721.67912 g 83.7 g
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.
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
Examples of rounding off
1st insignificant digit
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
a. 0.0431b. 9540c. 0.0000379d. 719
8.
What will the exponent for the power of 10 be when each of the following numbers is written in scientific notation?
a. 3981.2b. 0.0004521c. 453.9d. 0.994 x 102
a. 3b. -4c. 2d. 1
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:
1. Which is smaller, 1 x 10-7 or 1 x 10-3
2. Which is larger, 2.3 x 103 or 1.8 x 106