Metric Measurement

1
Metric Measurement
2
The Metric System
Created by French scientists in the late
1700s Goal of the system was to create a system
of measurement that was based on the decimal
instead of fractions. Single unifying system
used throughout the world. Only country that
does not use the metric system as a basic unit of
measurement is the United States.
3
Basic Units and Quantities
4
Basic Units and Quantities (contd)
5
Metric Prefixes
T tera 1012 1 000 000 000 000 trillion G giga 10
9 1 000 000 000 billion M mega 106
1 000 000 million k kilo 103 1
000 thousand h hecto 102
100 hundred da (D) deka 101
10 ten 100 1 d deci 10-1 0.1 te
nth c centi 10-2 0.01 hundredth m milli 10-3 0.
001 thousandth µ micro 10-6 0.000
001 millionth n nano 10-9 0.000 000
001 billionth p pico 10-12 0.000 000 000
001 trillionth
6
Measuring Length, Height, Width, Etc. . .

• When measuring length in science, we always use
  variations of the metric unit of measurement, the
  meter
• If our measurements are too small for the meter,
  (like the length of a pencil), we use variations
  of the meter, like centimeter or millimeter
• If our measurements are too large for the meter
  (like distances traveled), we use larger
  variations of the meter, like kilometer

7
Instruments Used to Measure Length, Height,
Width, Etc. . .

• In science, there are three basic instruments
  used to measure length
• For large objects, we use meter sticks
• For medium-sized objects, we use rulers
• -- make sure to use the cm side!!!
• For small objects (like in biology), we use the
  millimeter increments on our microscopes (more on
  using this later)

8
Measuring Mass
When we measure mass in science, we always use
variations of the metric unit for mass, which is
the gram For very large objects with lots of
mass (like cars), we would use the kilogram (1000
g). -- A lot of later formulas are based off of
the kilogram, so be careful which unit you need!
9
Instruments Used to Measure Mass
Normally, triple beam and double pan balances are
sufficient to find mass of most large objects,
however, they are NOT very accurate for small
objects INSTEAD We prefer to use the electronic
balances, which give mass in grams and are very
accurate -- You must remember to zero the
electric balance AFTER you have placed the
plastic measurement tray on!
10
Measuring Volume
We measure volume in science using variations of
the metric unit for volume, the cubic centimeter
(cm3) You must remember that 1 cm3 is EXACTLY
EQUAL to 1 milliliter (mL). ? This comes from
waters special definition (more on this
later) Usually, when we report volume, we report
it in mL, however, for large volumes, we use the
liter (1000mL).
11
Instruments Used to Measure Volume of Liquids
(and some solids)

• Its pretty simple The ONLY WAY to accurately
  measure volume is with a graduated cylinder
• Always read the measurement from the meniscus
  (middle of water bubble)
• -- DO NOT use a beaker
• -- DO NOT use an Erlenmeyer flask

12
Other Ways to Measure Volume
If an object is a perfect cube, we can calculate
its volume using a simple mathematical
formula Volume length x width x height, or V
lwh For instance, if we measure a small cube,
with sides of 2 cm each, we can easily
calculate its volume
L 2 cm H 2 cm W 2 cm V 2 cm x 2 cm x 2 cm
8 cm3
2 cm
2 cm
2 cm
We always measure the volume of a cube WITH A
RULER!!!
13
Measuring Volume of Non-Cube Shaped Solids

• If we want to measure volume of unusually-shaped
  solids, we use what is called the water
  displacement method.
• Steps to the Water Displacement Method
• Fill a large graduated cylinder with an known
  volume of water. Write this value down as Volume
  1.
• Place the object in the graduated cylinder until
  it is completely submerged.
• Record the new volume of water in the graduated
  cylinder. Write down this value at Volume 2.
• Volume 2 Volume 1 Volume of the solid, since
  you didnt add any water to the cylinder!

14
What do we do if our solid is too big to fit in
the graduated cylinder?

• Fill a tub, or other large object with water (it
  doesnt matter how much, just enough to submerge
  the object)
• Place the object in the tub.
• Draw a line on the tub at the new water level.
• Remove the object from the tub.
• Using a graduated cylinder, measure how much
  water it takes to fill the tub to the line. The
  amount of water that you add is the volume of the
  solid.

15
BORED YET???
16
Precision in Measurement
When we measure, we always add one digit BEYOND
the last known measurable digit -- That digit is
called the first uncertain digit FOR EXAMPLE
0 1 2
3 4
On the ruler above, the arrow is pointing between
2.4 and 2.5 cm. 2.4 cm is the last known digit.
We also must add the first uncertain digit to
show that our measurement is greater than 2.4,
but less than 2.5 cm. Therefore, the most correct
measurement would be something like 2.46 cm
17
Metric Conversions
Because the metric system is decimal-based, it is
very easy to convert between similar metric
amounts (like from centimeters to kilometers) The
only trick in moving from one metric level of
measurement is knowing which way to move the
decimal point (right or left) REMEMBER, when
going from bigger units to smaller units, your
number should always increase (you need more
smaller units to fit into one bigger unit) The
easiest method to remember is to use the METRIC
STAIRS
18
The Metric Stairs
kilo hecto deka deci centi
milli
When moving from bigger to smaller units (left to
right), we move our decimal one space to the
right for each step down (our amount will get
bigger!) When moving from smaller to bigger
units (right to left), we move our decimal one
space to the left for each step up (our amount
will get smaller!)
19
Practice Using the Metric Stairs
How many millimeters are in 24 decimeters? How
many kilograms are in 1734.26 centigrams? How
many liters are in 59 hectoliters? How many
kilometers will you have run if you run 550000 mm?