Transcript Metrics and Measurement

Fill in the notes sheet as we go!
Fundamental Units are the simplest way to measure
a quantity.


Sometimes also called base units
Quantity
SI Unit
Symbol
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
number of atoms or
molecules
mole
mol
Temperature
Kelvin
K
Electric current
Ampere
A
Amount of light
(intensity)
Candela
cd


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How is volume measured?
What units do we measure volume in?
Is volume a fundamental unit? Why or why not?
No! volume is measured in mL or L . But you can sometimes
measure volume as length x width x height.
 1 thousand liters is the same as a cube with sides of 1 meter. So
1000 L = 1 m x 1 m x 1m = 1 m3
 Thus volume is derived from length!
 By the way, this would LITERALLY weigh a ton ( if it was water)!
1 metric ton = 1 cubic meter of water (about 1.1 “regular” tons)

There are only 7 base units, but you can measure SO
MUCH more!
 Everything else you measure can be related to these

These other units are called derived units
 Example: speed is measured in meters/second (m/s)

MEMORIZE THESE!
Prefix (symbol)
Mega- (M)
kilo- (k)
centi- (c)
milli- (m)
micro- (m)
nano - (n)
Conversion
Factor
106
1,000,000
103
1000
10-2
1/100
10-3
1/1000
10-6
1 millionth
10-9
1 billionth
Example
1 MW = 106 W
1 kg = 103 g = 1000 g
1 cm = 10-2 m = 0.01 m
1 mL = 10-3 L = 0.001 L
1 ms = 10-6 s =
0.000001 s
1 nm = 10-9 m =
0.000000001 m
Suppose you want to convert from 342 cm to m.
1 centimeter is 1/100 of a meter
1 cm = 1/100 m
OR 100 cm = 1 m
We can also write this as two fractions called
conversion factors :
100 cm
OR
1m
1m
100 cm
But what do we do with these fractions???
1. Write out the equal quantities (100 cm = 1 m)
2. Write out the TWO conversion factor fractions
100 cm
OR
1m
1m
100 cm
3. You ALWAYS multiply by the conversion factor
when you convert!
Don’t forget to cross out units
when they cancel!
So 342 cm x 1 m
=
3.42 m
100 cm
You pick the conversion factor that will cancel out
the unit you started with!
Metric prefixes are used to put numbers into a more
usable format….
 For example:
 12000 g is better written as 12 kg
 0.0000065 m is better written as 6.5 mm

For ALL of your measurements and calculated
answers, make sure that you are using the most
logical unit for that measurement!

You will need to know a few basic conversions from
the Imperial system (what we use in the US) to the
metric system

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1 inch = 2.54 cm

1 mile = 1.6 km
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2.2 lbs = 1 kg

1 gal = 3.8 L

If markings are given every 10 mL…
 Estimate to the 1’s place (ex: 15 mL)

If markings are given every 1 mL…
Estimate to the tenths place (ex: 15.0 mL)

If markings are given every 0.1 mL…
 Estimate to the hundredths place (ex: 15.00 mL)
Making Measurements
Always read as many places as possible from the
instrument and then estimate one additional place.
The last number that you record is the one
you are uncertain about
Practice: Which digit did you estimate?
43.29
23
184.2
43.29
23
184.2
Partner Talk: why does it matter
that we record an “extra” digit?
Because you are COMMUNICATING how accurate your
reading is.
To a scientist, there is a BIG difference between 100 and
100.0!
100 tells a scientist that you are only certain to the nearest
100. This means you can’t tell the difference between 100
and 149! (both would round to 100)
But saying 100.0 means you are accurate the nearest tenth.
So now you know for certain you are close to 100
Example: An instrument reads to the nearest tenth. You
should estimate to the nearest _________________.
hundredth
Example: A scientist records a measurement as 23.4 cm.
The instrument must have increments of ____________.
1 cm
Partner talk: How long is the yellow cylinder?
1.25 cm (but you could say any # for the 5 and still be
correct! The “5” is YOUR estimated digit since the
instrument measures to the tenths place)