2 Objectives Recall units of measure Describe uncertainty in measurement Use scientific notation for numbersApply significant figure rules
3 Units of Measure SI Base Units Mass Kilogram – kg 1 kilogram is about 2.20 poundsLengthMeter – m1 meter is about 3 feet
4 Units of Measure Time Second – s The time needed for a cesium-133 atom to perform 9,192,631,770 complete oscillations.TemperatureKelvin – K273 K = 0 degrees CAmountMole – mol1 mol = 6.022x1023 particles
5 Units of Measure Current Ampre – A Luminous Capacity Candela – cd First five are the most commonly used in chemistry
6 Volume Volume is not an SI Base Unit Metric systemPowers of 101 Liter is 1/1000 of a cubic meter1 Liter (L) = 1000 cm3 = 1000 mL
18 Significant Figures Rule #5 “Exact Numbers” Exact number have an unlimited number of significant figuresExact numbers are counting numbers or definitions2 cars or 1000g/1kg
19 Significant Figures Rule #6 “Scientific Notation” All numbers that come before the x10n are significantMust be in proper formEx. 3.33x105Ex. 2.04x10-4
20 Rounding 5 and larger round up 4 and smaller round down Round the followingto 2 SF =to 4 SF =to 3 SF =to 2 SF =
21 Addition and Subtraction w/ SF The answer must have the same number of digits to the right of the decimal as there are in the measurement having the fewest digits to the right of the decimal pointEx m + 15 m =Number of SF’s does not matter!
22 Multiplication and Division w/ SF The answer can have no more SF’s than are in the measurement with the fewest total SF’sEx. 55 m / s =
23 Scientific NotationA method of representing very large or very small numbersM x 10nM is a number 1 or larger and less than 10n is an integer (positive or negative)All digits in M are significant (If in proper form)
24 Converting to Sci. Notation Move decimal so that M is between 1 and 10Determine n by counting the number of places the decimal point was movedMoved to the left, n is positiveMoved to the right, n is negative
26 Sci. Notation on Calculators Enter digits in you calculator using the EE key.For TI 83’s it is the 2nd of the commaFor TI 30’s it is a keySaves key strokesFewer OOR mistakes3.4x106 = 3.4E67.4x10-5 = 7.4E-5
27 Sci. Notatation Math Operations Multiply and DivideMultiply or divide first numberAdd exponents (Multiply)Subtract exponents (Divide)Addition and SubtractionExponents must be the sameThen add or subtract first numberExponents stay the same
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