A Standard Measurement System
• Term
Chapter 2: The Work of
Scientists
SI – system of international units; a system
of measurement related by multiples of 10
Measurement
- Measurement–A Common Language
A Standard Measurement
System (p. 45)
- Measurement–A Common Language
A. Length (p. 46)
• The basic unit of length in the SI system is
the meter (m).
Length- the distance between 2 points
SI unit = meter (m)
For small measures
use:
Centimeters (cm)
Millimeters (mm)
For very small
measures use:
Micrometers (mcm/µm)
Nanometers (nm)
These are microscopic
For large measures
use:
Kilometers (km)
Estimation of length
1 meter is
about as
high as a
door knob
on a
regular
door
The diameter of a CD is
about 12cm
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B. Mass- measures the amount of
matter in an object
Other definitions here:
Matter- anything that has mass and
occupies space
Weight- measurement of force that depends
on gravity. (gravitational force can change
depending on where an object is located)
Mass is measured on a balance.
Weight is measured on a scale which has a
spring to measure force.
- Measurement–A Common Language
Mass
• The basic unit of mass in the SI system is
the kilogram (kg).
SI unit for mass =
kilogram (kg)
1 liter of water has a
mass of 1 kg
Smaller masses are
measured in:
Grams (g)
Milligrams (mg)
C. Volume – the amount of space
an object occupies
• For a solid:
SI unit = cubic meter (m3)
small volumes use cubic
centimeter (cm3)
• Formula:
volume = length x width x
height
V=lxwxh
• A cube 10cm on a side
holds 1 Liter of water.
The solid volume of the
cube is 1000cm3.
V = 10cm x 10cm x 10cm =
1000cm3
Conversions:
1ml = 1cm3
1L = 1000cm3
1000ml = 1 L
- Measurement–A Common Language
Density
D. Density
Density Formula:
Density = mass
volume
D=m
v
• Because density
is actually made
up of two other
measurements–
mass and
volume–an
object’s density is
expressed as a
combination of
two units.
2
- Measurement–A Common Language
Calculating Density
• Suppose that a metal object has a mass
of 57 g and a volume of 21 cm3.
Calculate its density.
•
•
•
•
Read and Understand
What information are you given?
Mass of metal object = 57 g
Volume of metal object = 21 cm3
- Measurement–A Common Language
Calculating Density
• Suppose that a metal object has a mass
of 57 g and a volume of 21 cm3.
Calculate its density.
•
•
•
•
Plan and Solve
What quantity are you trying to calculate?
The density of the metal object = __
What formula contains the given quantities and the
unknown quantity?
• Density = Mass/Volume
• Perform the calculation.
• Density = Mass/Volume = 57 g/21 cm3 = 2.7 g/cm3
- Measurement–A Common Language
Calculating Density
•Suppose that a metal object has a mass
of 57 g and a volume of 21 cm3. Calculate
its density.
•Look Back and Check
•Does your answer make sense?
•The answer tells you that the metal object
has a density of 2.7 g/cm3. The answer
makes sense because it is the same as
the density of a known metal–aluminum.
- Measurement–A Common Language
- Measurement–A Common Language
Calculating Density
• Practice Problem
• What is the density of a wood block
with a volume of
125 cm3 and a mass of 57 g?
• 0.46 g/cm3
- Measurement–A Common Language
Time
Calculating Density
• Practice Problem
• The second (s) is the SI unit to measure
time.
• What is the density of a liquid with a
mass of 45 g and a volume of 48 mL?
• 0.94 g/mL
3
- Measurement–A Common Language
Temperature
• In addition to the Celsius scale,
scientists sometime use another
temperature scale, called the
Kelvin scale. The kelvin (K) is the
official SI unit for temperature.
Absolute Zero
• (0K)- coldest temperature possible
- Measurement–A Common Language
Converting Between Units
• Using the
appropriate
conversion factor,
you can easily
convert one unit of
measurement to
another.
• This example shows
how to convert 1.5
kilometers to meters.
- Measurement–A Common Language
Comparing and Contrasting
Characteristic
Definition
SI Unit
Measuring
Tool
Length
Mass
Time
Temperature
Distance from
one point to
another
Amount of
matter
Passing of
events
Hotness or
coldness
Meter (m)
Gram (g)
Second (s)
Degrees of
Celsius or
Kelvin
Metric ruler
Balance
Watch or clock
Thermometer
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