Units of Measurement Chapter 3

Using SI Units All metric units are based on multiples of 10, allowing you to convert easily between them. International System of Units (SI)- is a revised version of the metric system From base units, all other units can be derived

Units of Volume The SI unit for volume is meters cubed (m 3 ) The more common unit for volume is liters (L)

Temperature Temperature- measure of how hot or cold an object is. Determines the direction of heat transfer. Scientists use degree Celsius and kelvin as units of temperature Celsius scale- sets the freezing point of water a 0 oC and the boiling point at 100 oC. Kelvin scale- sets the freezing point of water at K and the boiling point at K. The zero on the Kelvin scale is absolute zero

Converting Between Kelvin and Celsius K= o C o C = K - 273

Dimensional Analysis The proper way to show the conversion between 2 different units of measurement

Conversion Factors Conversion factors- is a ratio of equivalent measurements When a measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quantity measured remains the same

Metric Conversions 1- Step If the base unit is found as the starting point or ending point to a dimensional analysis problem, it will be a 1- step problem Examples of base units: meters, seconds, liters, grams, bagels, dogs, etc….

m  cm How many centimeters are in 2.58 meters? 1- step problem because a base unit (m) is the starting point. Remember……. 1 ALWAYS goes with the prefix 2.58 m1 cm2.58 x 10 2 cm m

Sig Figs? The sig figs represented in the starting point should be carried over to the ending point. Conversions are considered exact measurements and should not be used to determine sig figs in the final answer.

dag  g How many grams are in 6.5 decagrams? 1- step problem because a base unit (g) is the ending point 6.5 dag10 1 g65 g 1 dag

s  ks How many kiloseconds are in 9.80 x seconds? 9.80 x s1 ks9.8 x ks 10 3 s

Practice 1- Step Metric Conversions 720 mg  g 4.58 x 10 5 µL  L 5.00 m  mm

Metric Conversions 2- Step If the base unit is not found as the starting point or ending point to a dimensional analysis problem, it will be a 2- step problem Always go to the base unit as a first step

hm  dm How many decimeters are in 25.8 hectometers? 2- step problem because a base unit (m) is not the starting or ending point. Go to the base unit (m) in the first step 1 ALWAYS goes with the prefix 25.8 hm10 2 m1 dm2.58 x 10 4 dm 1 hm10 -1 m

mL  ML How many megaliters are in 639 milliliters? 2- step problem because a base unit (L) is not the starting or ending point. Go to the base unit (L) in the first step 1 ALWAYS goes with the prefix 639 mL10 -3 L1 ML6.39 x ML 1 mL10 6 L

Practice 2-Step Metric Conversions 55 µs  Ms 6.55 x km  mm 450 cg  hg

Non-metric Conversions A non-metric conversion will consist of 2 different base units How many inches are in 92.5 centimeters? 92.5 cm1 in36.4 in 2.54 cm

lbs  oz How many ounces are in pounds lbs16 oz612.0 oz 1 lb

Mixed Practice 4.5 x 10 3 s  yrs 250 cal  J 6.72 mg  carats

38 km/s  mi/hr km/s  mi/h

38 km1 mi60 s60 min8500 mi s1.609 km1 min1 hr