Measurement
The International System (S.I.) is a set of
standard unit of measurement for scientists
throughout the world.
Quantity
S.I. Base Units
Unit
ABBREV
Length
meter
m
Mass
kilogram
kg
Temperature
kelvin
K
seconds
s
Time
Volume
cubic meter
m3
S.I. prefixes are added to the base units to
increase or decrease their value by powers of
10.
Numerical Symbol Meaning Multiplier Exponential
prefix
Multiplier
kilo
k
thousand 1,000
1 X 103
deci
d
tenth
1 X 10-1
centi
c
hundredth 0.01
1 X 10-2
milli
m
thousandth 0.001
1 X 10-3
0.1
Converting within a specific quantity requires
moving the decimal place.
Example: 546 µm = .000546 m
Example: 0.00056 kL = 560 ml
Example: 1000 g = 1 kg
The Metric Number Line
We are mostly interested in measurements from the kilo to
milli – region of the number line. Use a device to help you
remember the order of the prefixes. Kind Hearted Dads Make
Dark Chocolate Milk
Length is the distance
covered by an object.
Unit of measure for
length is the meter
(m). The instrument
used to measure
length is a ruler, meter
stick, etc.
Mass is a measure of the quantity of matter
in an object. Mass does not change with
location. The unit used for mass is the gram
(g). The instrument we use to measure mass
is a balance.
Weight is a measure of the
force of gravity between
objects. Weight will vary
with location and the unit
of measure for weight is
the Newton (N). The
instrument we use to
measure weight is the
spring scale.
Temperature is a measure of the average
kinetic energy of the particles in a sample of
matter. We usually measure in Celsius (0C)
then change to Kelvin (K) when needed.
The instrument used to measure
temperature is the thermometer.
Kinetic energy is the energy an object has due to
its motion.
Gas molecules move faster than the molecules in
solids and liquids, and therefore, have more
kinetic energy.
Gas molecules
Liquid molecules
Solid Molecules
Heat is the energy transferred as a result of a
temperature difference.
Left undisturbed, energy will flow from
objects of high temperature to objects of low
temperature until the objects have equal
temperature.
Unit – Joules (J) or Calories (cal)
1 cal – 4.184 J
1000 cal = 1 kcal also called 1 food Calorie
A calorimeter is the
Instrument used to
measure energy.
Volume is the amount of
space occupied by an object.
SI is m3 (too big!) =
length X width X height
1 dm3 = 1 L
1 cm3 = 1 mL
1000 mL or cm3 = 1 L or dm3
The instrument we use most
often to measure volume is
the graduated cylinder.
Accuracy is how close a measurement is to
the actual(accepted) value.
Example: Your watch is accurate
if it is close to that kept by the
National Institute of Standards
and Technology (N.I.S.T.)
Error:
Experimental error-difference
Between yours & actual value
Percent error = Experimental error x 100
Actual value
Example: on board
Precision is how close
a set of
measurements are to
each other.
(repeatability)
Example: A field goal
kicker is precise if he
kicks the ball through
the goal posts every
time.
Significant Figures or Digits
The number of reliable digits in a
measurement based on accuracy of the
measuring instrument.
The last digit in the number may be an
estimated one.