CHEMISTRY 161 Chapter 3 Measurements Measurements measurements are
- Slides: 14
CHEMISTRY 161 Chapter 3 Measurements
Measurements measurements are numerical (quantitative) observations how much? weight; volume; speed; energy; density; distance qualitative observations what? color, small
Measurements number error* *uncertainty unit
SI base unit measurement length mass time electrical current temperature amount of substance luminous intensity unit meter gram second ampere Kelvin mole candela symbol m g s A K mol cd all units are derived from 7 SI base units
derived units area length width volume length width height velocity distance / time acceleration velocity / time Force [N] Pressure [Pa; mbar, torr] acceleration mass force / area
Measurements number unit 50 m s-1 300, 000 m s-1
Decimal Multipliers prefix mega kilo deci centi milli 1000 g symbol factor power of 10 M 1000000 106 k 1000 103 d 0. 1 10 -1 c 0. 01 10 -2 m 0. 001 10 -3 0. 01 g 0. 001 g
Conversion Measurement English to Metric to English Length 1 ‘’ = 2. 54 cm 1 m = 39. 37 in. 1 yd = 0. 9144 m 1 km = 0. 6215 mile 1 mile = 1. 609 km Mass 1 lb = 453. 6 g 1 kg = 2. 205 lb 1 oz = 28. 35 g Volume 1 gal = 3. 785 L 1 L = 1. 057 qt 1 pt = 946. 4 m. L 1 oz (fluid) = 29. 6 m. L 1 L = 1000 m. L = 1000 cm 3
Temperature 0 K -273 OC
NASA-Mars Polar Lander
Measurements number error unit measuring device inaccurate reading multiple measurements average (statistics)
Significant Digits T = 24. 3 ºC (3 significant digits) T = 24. 32 ºC (4 significant digits) 0. 034 K 3. 4 10 -2 0. 0340 K 3. 40 10 -2 combining significant digits
Summary 1. SI units and conversion of units 2. 2. error 3. 3. number of significant digits
