Why are these important?
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SI stands for Systeme International d’Unites
Internationally, this is the system that we will
use measure anything in science.
There are several things that get measured
Length, Mass, Volume/Area, Density, Time,
Temperature
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Measured in Meters
(m)
How long something
is or the distance
between two objects
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Measured in grams
(g)
The amount of matter
in an object
Not the same as
weight but similar
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Area is measured in
m2
It is the amount of
space on the surface
something takes up.
Volume is measured
in the liter (L) or m3
Amout of space
something takes in 3D
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When measuring
from a graduated
cylinder or a beaker,
measure at the bottom
of the meniscus
(natural curve that
water makes in a
container)
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Amount of matter that
occupies a given space
Doesn’t have a special
unit to itself.
Labeled g/mL or
g/cm3
Aka mass/volume
No tool to measure
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Internationally time is
measured by seconds
(s)
Usually is going to be
measured by a watch
or a timer
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In science we do no
use the Fahrenheit
scale. We use Celcius
(C°)
We could also
measure in Kelvin but
that’s less important
at the moment
Use a thermometer
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Unit is whatever you are measuring in. It is
described as any of the SI measurements that
are used
Denoted with a u
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There are bigger and
smaller units of each
base units
Length-meter(m)
Mass- gram (g)
Volume- Liter (L)
Time- second (s)
Temperature- Celcius
(C°)
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Prefixes will go in
front of the base unit.
Prefixes are: kilo-,
hecto-, deka-, deci-,
centi-, milli-, micro-,
nano-, picoKing Henry Doesn’t
[Usually] Drink
Chocolate Milk
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Kilo(k)- kilogram (kg), kilometer (km), kiloliter
(kL), kilosecond (ks), kilounit (ku)
1ku= 1000 u (1000 of your base unit)
1u= .001 ku
Hecto(h)- hectogram (hg), hectometer (hm),
hectoliter (hL), hectosecond (hs), hectounit (hu)
1 hu= 100 u (100 of your base unit)
1 u= .01 hu
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Deka(D)- dekagram (Dg), dekameter (Dm),
dekaliter (DL), dekasecond (Ds), dekaunit (Du)
1Du= 10 u (10 of your base unit)
1 u= .1 Du
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Deci(d)- decigram (dg), decimeter (dm),
deciliter (dL), decisecond (ds), deciunit (du)
1 u= 10 du (10 du in your base unit)
1du = .1u
Centi (c)- centigram (cg), centimeter (cm),
centiliter (cL), centisecond (cs), centiunit (cu)
1 u= 100 cu (100 cu in your base unit)
1cu= .01 u
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Milli (m)- milligram (mg), millimeter (mm),
milliliter (mL), millisecond (ms), milliunit (mu)
1 u= 1000 mu (1000 mu in your base unit)
1 mu= .001 u
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Quick Review….
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1 m = ? mm
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1ms= ? s
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1 L = ? cL = ? mL
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1 L = ? mm
HINT!
If you are getting
bigger divide.
If you are getting
smaller multiply
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Accuracy- is a measure of how close a
measurement comes to the actual value of
whatever is measured.
Ex. Darts land close to the bull’s-eye
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Precision- the measure of how close a series of
measurements are to one another
Ex. The darts are all very closely grouped
together. (Don’t have to be near bull’s-eye)
If something is precise it isn’t always accurate.
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The density of a certain metal is 2.45 g/mL.
You measure densities of 2.01 g/mL, 1.99
g/mL and 2.03 g/mL. Accurate, precise, or
both?
You measure densities of 2.45 g/mL, 2.50
g/mL, and 2.47 g/mL. Accurate, precise, or
both?
You measure densities of 1.57 g/mL, 3.01
g/mL, and 2.45 g/mL
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Accepted value- The correct value based on
reliable references
Experimental value- The value measured in the
lab
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Error is the difference between the
experimental value and the accepted value.
Error= experimental value- accepted value
The density of gold is 19.30 g/mL. You do a
experiment and find a density for gold of 20.50
g/mL. What is the error in your experiment?
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Error can be positive or negative depending on
whether the experimental value is great than or
less than the accepted value.
Percent error is the absolute value of the error
divided by the accepted value, multiplied by
100%.
Percent error= error/(accepted value) x 100%
Gold PE = 1.20(g/mL)/19.30(g/mL)x 100%
Gold PE = 6.21%
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In many branches of science, some numbers are
very small, while others are quite large. To
convieniently express these numbers, scientists
use a short hand called scientific notation.
Expresses a number as a multiplier and power
of 10.
If the decimal point is shifted right the power
of 10 is negative
If the decimal point is shifted to the left, the
power of 10 is positive.
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I’m passing out a sheet. This is my reminder to
myself… Don’t laugh at me