CH1010 Lecture 2

Ch1010 lecture 2

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Unformatted text preview: Molecularity Molecularity CH1010 Lecture 2 James P. Dittami Convert 2.85 cm to inches Dimensional Analysis Dimensional Analysis Converting from one system of units to another Look up equivalence statement So 1 in 2.54 cm = 1 in or 2.54 cm NOTE: Exact Numbers Now set up so units cancel 2.85 cm x 2.54 cm 1 in cm cancels ­ NOTE answer has 3 sig. figs. 1 in = 2.54 cm 1.12 in Convert 7.00 inches to cm 7.00 in x 2.54 cm = 17.8 cm 1 in Note 3 sig. figs. in 7.00 and answer 17.8 2.54 cm/1 in has infinite sig.figs. 2.54 cm/1 in and 1 in/ 2.54 cm are “Unit Factors” Dimensional Analysis Dimensional Analysis Converting from one system of units to another Practice Problems Practice Problems For Practice see examples in Text­ Especially Examples 1.2­1.12 Temperature Scales Temperature Scales Three Scales Celsius Symbol = °C Kelvin Symbol = K Fahrenheit Symbol = °F Can relate all to b.p. or f.p. of water The freezing and boiling points of water. Temperature Scales and Interconversions Kelvin ( K ) - The “Absolute temperature scale” begins at absolute zero and only has positive values. o o T (in K) = T (in oC) + 273.15 T (in oC) = T (in K) - 273.15 T (in oF) = 9/5 T (in oC) + 32 T (in oC) = [ T (in oF) - 32 ] 5/9 Celsius vs. Kelvin Celsius vs. Kelvin Temperature Unit is same size Zero Point Differs So in general for conversions: 0 ˚C = 273.15 K 0 K = ­273.15 ˚C Tk = Tc + 273.15 Tc = Tk – 273.15 Celsius vs. Fahrenheit Celsius vs. Fahrenheit Degree size is different­ must adjust Range of freezing to boiling is 180 ˚F Units = 100 ˚C Units So 180 ˚F /100 ˚C = 9 ˚F /5 ˚C Zero Point is also different 32 ˚F = 0 ˚C Celsius vs. Fahrenheit Celsius vs. Fahrenheit TC = 5/9 (TF­32) TF= 9/5 TC + 32 ˚F Density Density Density = Mass Volume Density = Mass / Unit Volume of Substance Really important in chemistry Compare block of wood vs. block of lead Huge difference in weight! Lift bushel of feathers vs. bushel of apples Same volume – different weight Calculations with Density Calculat...
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This note was uploaded on 02/14/2011 for the course CH 1010 taught by Professor Kumar during the Spring '06 term at WPI.

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