1 The Metric System Mr. ShieldsRegents Chemistry U00 L03

2 barleycorns ??? In Anglo-Saxon England (before the Norman conquest of 1066) the inch (ynce) was defined to be the length of 3 barleycorns ??? (Of course we all know how large a barleycorn is right???) -A foot = 36 barleycorns = 12 ynce (36/3)

3 Area 1 acre = size of a field a farmer could plow in 1 day –Hmmm …

– French Academy of Sciences created the Metric System The unit of length was to be a portion of the Earth's circumference (the std.) Measures for volume and mass were to be derived from the unit of length Larger and smaller multiples of each unit were to be created by multiplying or dividing the basic units by 10 i.e decimal system.

5 Since 1875 the United States has subscribed to the International System of Weights and Measures, the official version of the Metric System.

6 Length length The fundamental unit of length was named the meter.

What is a meter? originally defined as “1/10,000,000th of the distance from the Equator to the North Pole measured along the meridian that runs through Dunkirk, France.” currently defined as the “distance a beam of light travels in 1/299,792,458 of a sec.” – That’s 1 / speed of light – which is also exactly inches.

Metric Prefixes PrefixSymbolValuePowerExample megaM1,000, megaton kilok1, Kilometer or kilogram decid decimeter centic centimeter millim Millimeter or milliliter micro  micron nanon nanotechnology gigaG1,000,000, gigabyte

9 Mass (Kg) The Fundamental unit of mass is the Kilogram (Kg) Defined as the mass of one cubic decimeter (0.1m x 0.1m x 0.1m) of water

*What is a kilogram? The fundamental S.I. unit for mass is the kilogram. It’s defined as the mass of 1 dm 3 (1 liter) of water at 4°C. 1 dm Recall… 1 dm = 0.1m or 10 cm

11 Volume The S.I unit for volume is the m 3 This is a derived unit. Derived units are obtained by multiplying or dividing Basic units (in this case length)

What is a Liter? A common unit used in volume measurement is the liter. The Liter was defined as a cube measuring 1 decimeter on each side, i.e. 1 dm 3, or in cm it’s 1000 cm 3. 1 dm So how much does a liter of water weigh?

What is a kelvin? The S.I. unit for temperature is the kelvin A difference of 1 degree kelvin (K) and 1 degree Celsius (°C) is exactly the same size (1 deg K = 1 deg C) To convert: °K = °C The kelvin is based on absolute zero (the coldest temperature possible.)

*What is a second? The Fundamental S.I. unit for time is the second. It was originally defined as 1/86,400th of the average solar day. It’s now defined using some large number of atomic vibrations of the Cs-133 atom. – Basis of the “Atomic Clock”

What is a mole? The fundamental SI unit for counting is defined as x of anything We’ll discuss this important concept at a later time The Mole !

There are 7 fundamental units in the SI System QuantityUnit nameAbbreviation lengthmeterm masskilogramkg temperatureKelvin (not Centigrade) K timeseconds (or sec) amountmolemol The Ampere (A) and the Candela (cd) are the other 2

Derived Metric Units There are several other important units used for volume measurement - Milliliter and liter (1dm 3 ) – 1 liter (l) = 1000 milliliter (ml) – 1 ml = L = 1 cm 3 (sometimes referred to as “cc” in the medical field) – So … 1 Liter = how many cm 3 and how many ml? A combination of several fundamental units

Other Key Derived Metric Units The JOULE – Unit of ENERGY – Ex. Heat, Kinetic & Potential Energy Comparable to the calorie The PASCAL – Unit of PRESSURE – Force/area – Ex. Atmospheric and gas pressure Comparable to mm or inches of Hg