The SI System of Measurement

The SI System of Measurement• The system of measurement that is in everyday

use in the United States is based on the Imperial (British) system of measurement.

• This system uses the foot, pound, and second as basic units.

• One problem with this system is that smaller or larger increments are not standard.

The SI System of Measurement• The Imperial System of measurement is illogical.

The SI System of Measurement• The S.I. system of measurement (a metric

system) was first established in France in 1791 as a result of the French Revolution.

The SI System of Measurement• The adoption of this system by the French

revolutionaries was a manifestation of the Age of Reason. They wished to establish a “rational” basis for every aspect of life, and the decimal system satisfied such a scheme.

The SI System of Measurement• They were also able to rid all measurement from

being linked to a monarchy.

The SI System of Measurement• As it turns out the S.I. (metric) system has a

further advantage in that the units are absolute since the units are not defined in such a way that local variation would change.

The SI System of Measurement• The metric system is sometimes called the

“mks” system for three of its base units; the meter, the kilogram, and the second.

• A base unit is a fundamental (elementary) unit.

The SI System of Measurement• In the S.I. system, there are seven base units:

The SI System of Measurement• Everything that people know how to measure

can be measured using the seven S.I. base units or units derive from them.

• The following S.I. derived units are very important in chemistry:

– The pascal (Pa) is the S.I. derived unit of pressure.

[Pa = kg/m·s2.]

– The joule (J) is the S.I. derived unit of energy.

[J = kg·m2/s2.]

The SI System of Measurement• The following are three important non-S.I. metric

units:

– The liter (L) is a metric unit for volume.

– The calorie (cal) is a metric unit of energy.

– 1.0 calorie is equal to the amount of heat needed to raise the temperature of 1.0 g of water 1.0oC.

– 1 (food) Calorie = 1000 (science) calories!

– The degree Celsius (oC) is a metric unit of temperature.

The SI System of Measurement• S.I. prefixes can be used with metric units to

form new units.

• The following are common S.I. prefixes: – kilo k 103 thousand

– deci d 10-1 tenth

– centi c 10-2 hundredth

– milli m 10-3 thousandth

– micro μ 10-6 millionth

– nano n 10-9 billionth

– pico p 10-12 trillionth

The SI System of Measurement

• Ex.(1) 164.4 cm = ______________________m

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

c

no prefix

k d c m μ n p

1.644

The SI System of Measurement

• Ex.(2) 0.0000536 dm = _________________pm

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

d

k d c m μ n p

5360000 p

The SI System of Measurement

• Ex.(3) 0.00167 μcal = _________________kcal

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

μ

k d c m μ n p

0.00000000000167 k

The SI System of Measurement

• Ex.(4) 19063 μcal = _________________ncal

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

μ

k d c m μ n p

19063000 n

The SI System of Measurement

• Ex.(5) 0.000063 ms = _________________ns

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

m

k d c m μ n p

63 n

The SI System of Measurement

• Ex.(6) 100035 cs = _________________ks

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

c

k d c m μ n p

1.00035 k

The SI System of Measurement

• Ex.(7) 1736000 pL = _________________μL

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

p

k d c m μ n p

1.736000 μ

The SI System of Measurement

• Ex.(8) 39.74 J = ______________________kJ

3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12

k

no prefix

k d c m μ n p

0.03974