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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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