Standards of Measurement
Physical Science
Mr. Bostrom
Units and Standards
1. Standards – exact quantity that people
agree to use for comparison
2. SI – standard system of measurement
1. All scientists use this system
2. Metric vs English System
1. Americans use the English System
1. Example: Feet and Inches
2. 1970’s we tried to convert to the metric system
1. We failed miserably
Common SI Prefixes
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Prefix
Meaning
Mega (M)
1000000
Kilo (k)
1000
Hecto (h)
100
Deka or Deca (da) 10
Base Unit
1
Deci (d)
0.1
Centi (c)
0.01
Milli (m)
0.001
Micro (µ)
0.000001
Nano (n)
0.000000001
Pico (p)
0.000000000001
SI Base Units
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Length – Meter (m)
Liter – Volume (L)
Mass – Gram (g)
Time – second (s)
Electric Current – Ampere (A)
Temperature – Kelvin (K)
How do prefixes and base units
work together
• Example: Kilogram or kg
– Kilo = 1000
– Gram is the base unit of mass
– 1 Kilogram = 1000 g
Converting within the Metric
System
• Rule #1:
Always remember that your
base unit is 1
• Rule #2: If you add a prefix onto the base
unit you multiply by what the
prefix represents
– Example: 1 kg = 1000 g or (1000 x 1)
2 kg = 2000 g or (1000 x 2)
What do you do when you are not
starting from or converting to your
base unit?
• Example: 100mm = ?km (This is where it
can get tricky)
• The rule of thumb is:
– If you are increasing in size you move the
decimal point to the left
– If you are decreasing in size you move the
decimal point to the right
• km are bigger than mm so you move the
decimal to the left
Sounds simple but how many
decimal places do you move?
• In this case 6
– How did I know that
– There are 4 ways to do this:
• First way: divide the prefix value of the
measurement you are starting with by the prefix
value you want to convert to and then multiply the
answer by the coefficient
» Milli = .001, Kilo = 1000
( .001/1000) x 100 = 0.0001 (This is the final answer)
You know it was six places because you started with
100.0 and to get 0.0001 you need to move the
decimal 6 places to the left
Converting Contineud
Second Way:
Kilo Hecto Deca Meter Deci Centi Milli
a. Find the prefix you are starting with
b. Then find the prefix you are converting to
c. Count how many prefixes you must pass to get to the
final prefix
- Always remember:
1. if you are getting larger the decimal goes to the
left
2. If you are getting smaller the decimal goes to the
right
3rd Way
• To convert from larger to smaller units,
multiply the coefficient by the difference
between units
• To convert from smaller to larger units,
divide the coefficient by the difference
between units
Example: 1 million mm in a km, so divide
100 by 1000000
4th Way
Factor-Label Method
• Multiply your coefficient by conversion
factor that equals one:
– Trying to convert mm to km
• 1 km = 1000000mm
– The conversion factor is (1 km/1000000 mm) = 1
– Example: 100 mm x (1km/1000000mm)
• 1 km/1000000mm = 1
Volume
• Defined as the amount of space occupied
by an object
• It does not just measure liquid
How do you calculate volume
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Liquid – with a graduated cylinder
Solid (2 possible ways)
1. Measure the height, length, and width and then
multiply the three.
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Length x Width x Height
2. For a solid in which you can’t measure the
length, width, and height you need to use a
measuring cup or graduated cylinder
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Using a graduated cylinder record a known volume of
water and then drop the object into the water
Record the new volume
Take the difference between the two volumes and that is
the volume of the object
What unit is volume recorded in?
• Because you are measuring height, width,
and length the unit is cm3
• Volume of a liquid would be in liters
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1 cm3 = 1 ml
• When you combine SI units the outcome is
known as a derived unit.
– Examples: meters/second
grams/ml
Density
• Mass per unit volume of a material
• Units for density are generally g/cm3
• To determine an objects density you need
to divide the object’s mass by it’s volume
– Example: If an object weighs 5 g and has a
volume of 10 cm3 what is the object’s density
• 5 g / 10 cm3 = .5 g/ cm3
• The density of water is 1 g/ml
Temperature
• Generally measured in Celsius (°C) for
most scientific work, however the SI unit
for temperature is Kelvin (K)
– How do you convert K to °C or °C to K?
• To convert °C to K you need to add 273
K = °C + 273
• To convert K to °C you need to subtract 273
°C = K - 273