introduction to chemistry systems of measurement professor bob kaplan university department of...

INTRODUCTION TO

CHEMISTRY

Systems of Measurement

Professor BobKaplan University Department of Science

Universe is composed of

Particles or Elements Theory of mechanism Scientific method Physical properties Systems of measurement (English, SI) Standardized units of measurement

Qualitative observations are subjective as well as descriptive.

Quantitative observations are objective,

and expressed numerically with

specific units

A Unit is a defining quantity for a measurement.

The Unit of Measure tells what scale or standard is being used to measure.

Units of Measurement:

Grams , Meters , Degrees

Numerical Value Real Number: 43.2

Unit of Measurement: Grams, Meters, Degrees E.G.  43.2  kg

Mass: kilogram (kg)Length: meters (m)Time: seconds (s)

Temperature: Degrees Fahrenheit (°F)

Numbers > 10

FactorKilo : 103 1,000

Mega : 106 1,000,000 Giga : 109 1,000,000,000

Numbers < 10

Deci : 10(-1)= 0.1 of the unit

Centi : 10(-2) = 0.01 of the unit

Milli : 10(-3) = 0.001 of the unit

Micro : 10(-6) = 0.000001 of the unit

Nano : 10(-9)= 0.0000000001 of unit

Length is the shortest distance between two points in space

1 - dimension

SI Unit: Meter (slightly longer than one yard)

Area is the planar space determined by the intersection of two lines in space

2 - dimensions

SI Unit of area Square meters

1 sq meter = 1 m2

= 1.21 sq feet = 1.21 ft2

Bulk quantity of space occupied by the intersection of two planes

3 - dimensions SI Unit:

Cube measures 1 meter on each edge

Volume of the cube 

=  length  x  width  x  height =  1 m  x  1 m  x  1 m =  1 cubic meter = 1 m3

If the cubic meter were divided into 1000 equal smaller parts, each part would be equal to 1 Liter (slightly larger than a quart)

1 qt = 1.057 L

If each liter were divided into 1000 equal smaller parts, each part would be equal to

1 milliliter (mL) or 1 cubic centimeter (cc)   1 mL = 1 cc  ~ 10 drops

1 meter = 39.37 inches

1 meter = 1.1 feet

1 inch = 2.54 cm

1 km = 0.621 miles

Glassware

Graduated Cylinder                 Volumetric Flask                      Pipet, Buret             Syringe, Eyedropper

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SI Unit: gram (g) or kilogram (kg)

1 kg = 1000 g

Determined by comparison with known standards on an analytical balance.

1 kg = 2.2 lb 454 g = 1.0 lb

General:

Amount or number per unit of measure. e.g.  Number of dust particles per cubic foot e.g.  Number of  inhabitants per square mile

(population density)

Physics & Chemistry: Amount of mass per unit volume

Mass  /  Volume  =  m / v

Units: g / ml   or   g / cc

Cork 0.24

Wood 0.75

Water 1.00

Cement 3.00

Lead 11.30

Gold 19.30

Heat is the motion, or kinetic energy, of atoms and molecules.

Temperature is an average measure of the intensity of heat motion.

There are several scales used to measure temperature:

Celsius (°C) Fahrenheit (°F)

Kelvin (K)

When the doctor says that your temperature is 102 degrees, or the weatherperson says that it will be 75 degrees tomorrow, they are using the Fahrenheit Scale.

Water Boils @ 212 °F Water Freezes @ 32 °F

Scale was designed by Gabriel Fahrenheit, who used the average temperature of the human body as his referent.

Used in Canada & Europe, and in the physical and life sciences worldwide.

Water Boils @ 100 °C

Water Freezes @ 0 °C

This commonly used scale uses the points of phase transition (or states of matter) of water as its referent.

On both C and F scales, the unit of temperature is called a “degree”.

The size of the degree is different.

1 °C = 1.8 °F The zero point of reference is shifted.

°F  =  (1.8)°C  +  32

°C  =  (°F - 32)  / 1.8

Zero Kelvin No Atomic Motion

Kelvin unit equivalent to Celsius degree.

1 Kelvin = 1 degree C

°K = °C + 273 Water Freezes @ 273 °K Water Boils @ 373 °K

O Kelvins = - 273 degrees °C

In the natural sciences, we use the technique of dimensional analysis for solving story problems with various units.

The key to this technique involves the use of conversion factors in order to obtain the correct units of measure.

1) Eliminate the units given 2) Introduce the units required ** Express 40 grams in kilograms (40 g) * (1 kg / 1000 g) = 0.04 kg

*Note: 1 kg / 1000 g = 1000 g / kg

See handout in DocSharing

Dim_anlys.doc

Please review this document carefully.

Other useful handouts posted include:

Symbols.doc

Formulas.doc

If you have come here directly from the SC155 Seminar session, please return to the KU course platform now to continue with the live session of discussion, questions and answers

See you all there !

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