A very important part of science is being able to make very
accurate measurements. Since scientists all over the world must be
able to communicate their discoveries with each other, it is
important that all scientists use the same units of measurement.
The system of measurement used by all scientists is __The
International System of Units__, which is abbreviated as the __SI__
system and commonly referred to as the __Metric System__. The metric
system was developed in France about 200 years ago. The metric
system is based on repeating units of ten.

The SI (metric) unit for length is the meter. A meter is one ten millionth of the distance from the north pole to the equator. Prefixes are added to the word "meter" to describe things that are much longer or shorter than a meter. Some of these are:

1. centi=1/100th-- A centimeter (cm) is 1/100th of a meter.

2. milli=1/1000th-- A millimeter (mm) is 1/1000th of a meter.

3. kilo=1,000 A kilometer (km) is 1,000 meters

Most people in America don't use the metric units to describe
length. Instead, most Americans use the __English system__ which
describes length in terms of inches, feet, yards, and miles. The
following gives you an idea of how these systems compare with each
other.

1. One inch is equal to 2.54 centimeters.

2. One foot is equal to 30.48 centimeters.

3. One meter is equal to 39.37 inches.

4. One mile is equal to 1.609 kilometers.

5. A very common running event is the 5k race. A 5k race is really a 5km race. Five kilometers is equal to about 3.1 miles.

6. 100 meters is equal to about 110 yards.

The amount of space on the surface of something is called its __area.__
The basic SI unit for area is the __square meter__ (m^{2}). Areas which
are composed of squares or rectangles are computed by multiplying
the length by the width. This is abbreviated by the formula:

A = L X W. The answer is always expressed in "square" units.

A common way that real estate people and appraisers describe the living area of a home is in square feet. A home which is 50 feet long and 30 feet wide would have 1,500 square feet of living area. Carpet and other flooring is sold by the square yard.

__Volume__ is the amount of space something occupies. A cube is a
three dimensional container having 90 degree angle walls. Our
classroom, for example, is a cube. It has three dimensions
(length, width and height) and the walls, ceiling and floor all
meet at 90 degree angles. The basic SI unit for volume is the
cubic meter (m^{3}). Volume is calculated by multiplying length by
width by height. This is abbreviated by the formula:

V = L X W X H. A swimming pool which is 20 meters long, 10 meters
wide and 2 meters deep would hold a volume of 400 cm^{3} of water.

Since the cubic meter is quite large, smaller units such as cubic
centimeters (ccm^{3}) are often used to describe volume. However, for
things which have a volume between that of a cubic centimeter and
a cubic meter, the __liter__ (L) is commonly used. A liter is the
volume of a cube 10 cm on each size. Soft drinks are often sold by
the liter or two liter bottle. A liter is almost the same as the
English unit of volume known as the quart. A quart is 32 fluid
ounces and a liter is 33.8 fluid ounces. For very small volumes,
the milliliter (mL) is often used. A milliliter is 1/1000th of a
liter.

If you want to know the volume of an irregularly shaped object, it
is best to place it in a graduated cylinder containing water. The
amount of water displaced by the object is equal to the volume of
that object.

__Mass__ is the measure of the amount of matter in an object. On the
earth's surface, mass is equal to weight. The SI unit for mass or
weight is the __gram__ (g). A kilogram (kg) is 1,000 grams. One
kilogram is equal to about 2.2 pounds. A milligram (mg) is
1/1000th of a gram.

__Density__ is mass (weight) per unit of volume. If you have equal
volumes of gold and styrofoam, the gold will weigh more even though
their volumes are the same. The gold weighs more because gold has
a greater density than styrofoam. Density is equal to mass divided
by volume: D = M/V. The answer is expressed as __mass per volume__.
A common metric expression of volume would be g/cm^{3}, which means
grams per cubic centimeter.

The SI unit for temperature is __degrees Celsius__ (C). The scale for
measuring temperature is the __Celsius scale__, a.k.a. the __centigrade
scale__. On the Celsius scale, water freezes at zero degrees and
boils at 100 degrees.

The English unit for measuring temperature is __degrees Fahrenheit__
(F). On the Fahrenheit scale, water freezes at 32 degrees and
boils at 212 degrees.

To convert centigrade to Fahrenheit the following formula is used:
F = 1.8 X C + 32

To convert Fahrenheit to centigrade the following formula is used:

C = .56 X (F - 32) ***remember to do what is inside of the
parenthesis first.

There is another scale for measuring temperature which is often
used in physics and chemistry. This is the __Kelvin scale__. The
Kelvin scale is just like the Celsius scale except that you add 273
degrees to degrees Celsius. So on the Kelvin scale, water freezes
at 273 degrees and water boils at 373 degrees. The Kelvin scale
was designed so that zero degrees Kelvin is __absolute zero__.
Absolute zero is the coldest possible temperature. Absolute zero
occurs with the complete absence of heat. Specifically, it is
273.16 C, or 459.7 F.

The SI units for time are seconds, minutes and hours. There are 60
seconds in a minute, 60 minutes in an hour, and 24 hours in a day.

Graphing: A graph is a good way of looking at data to find
possible relationships. __A graph is a picture of data__. Graphs
usually have these features:

1. abscissa--the horizontal or X axis

2. ordinate--the vertical or Y axis

3. origin--the place where the horizontal and vertical axes meet.

Lab. assignment: In your group, conduct the following experiment
and graph the results. With a rubber band attached to the end of
a ruler, stretch the rubber band to varying distances. Release the
rubber band and allow it to be propelled. Measure how far back the
rubber band was stretched and how far it traveled. Graph the
results. On the X axis, plot the length which the rubber band was
stretched. Stretch it to at least five different lengths. On the
Y axis, plot how far the rubber band traveled. This lab. activity
is worth 50 points for each student. If another person is shot
with the rubber band, a ten point penalty will be deducted from the
grade of the shooter each time this occurs. When finished, turn in
your graph. Be sure to include the names of all people who
participated in the group.

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