Transcript Units of Measurement - West Orange Public Schools

Do Now: Arrange the following steps of the
scientific method in order:
___ Form a hypothesis
___ Collect data
___ State the problem
___ Test the hypothesis with an experiment
___ Conclude
___ Organize and Analyze data
Units of
Measurement
What are measurements?
Measurements are a comparison
between the quantity being measured
and a certain standard quantity called a
unit of measurement.
International System of Units (SI)
The metric system or the
international system of units (SI) is
the system of standard units that is
used around most parts of the
world and in the field of science.
The US uses the English system for
measurements, whereas, the rest of the
world uses the metric system. Most people
in the world know exactly how long a
kilometer is, how large a liter is, how much a
kilogram weighs, and how warm 25°C is,
because they use these units everyday of
their lives in the same way Americans use
miles, gallons, and pounds.
The field of science uses the metric system
for measurements. Before an actual system of
measurement was adopted, the king’s
measurements were used. For example, the
distance between the king’s knuckle to the tip of
his finger was considered an inch. The king’s foot
was a foot. Every time the king changed, the
measurements changed. This was not an
accurate means for measurement.
Base units
There are seven base units in the
SI. A base unit is a unit of
measurement that is based on an
object or event in the physical
world.
SI Base Units
Physical Quantity
• Mass
• Length
• Time
• Temperature
• Quantity
• Electric Current
• Luminous intensity
SI Unit
kilogram (kg)
meter (m)
seconds (s)
Kelvin (K)
mole (mol)
ampere (A)
candela (cd)
The decimal system
SI is based on a decimal system. Multiples
and fractions of the fundamental units are
created by adding prefixes. Prefixes are
used to extend the range of SI units.
Prefixes
Prefix
KiloHectoDecadecicentimillimicro-
Symbol
K
H
D
1
d
c
m
µ
Factor
1,000
100
10
0.1
0.01
0.001
0.000001
Derived Units
Not all quantities can be measured using the
SI base units. For example, volume and
density are measured using units that are a
combination of base units. A SI unit that is
defined by a combination of base units is
called a derived unit.
Derived Units Commonly Used
in Chemistry
Quantity
Area
Volume
Force
Pressure
Energy
Voltage
Frequency
Electric charge
Unit Name
square meter
cubic meter
newton
pascal
joule
volt
hertz
coulomb
Symbol
m2
m3
N
Pa
J
V
Hz
C
Metric conversions
EXAMPLE 1:
103 kg  Dg
Example 2
.43 dg  mg
Example 3
2,132 cm  hm