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Metric Measurement

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.

Basic Units and Quantities

Basic Units and Quantities (contd)

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

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

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)

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!

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!

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).

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

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!!!

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!

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.

BORED YET???

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

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

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!)

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?