Measurement and Dimensional
Analysis
The Importance of Measurement
A. Measuring is a fundamental skill of science.
B. Without measurements we could not
describe our observations.
Measurements provide a standard.
A. Two types of measurement
1. Quantitative measurements- give results in
a definite form, usually as numbers.
ex: “The car weighs 2000 kg.”
2. Qualitative measurements- give results in
a descriptive nonnumeric form.
ex: “The car is blue.”
The Metric System
A. Although the United States still uses
the English system of measurement,
the rest of the world has switched to a
standard form of measurement known
as the metric system.
What metric units do you know?
A. Give a metric unit of measurement for
the following quantities:
1.
2.
3.
4.
Mass
Temperature
Volume
Time
Base Units in the Metric System
A. Base units are defined based on something
observable object or event in the world
1.
2.
3.
4.
5.
6.
7.
length- meter(m)
mass- gram(g)
time- second(s)
electric current – ampere(A)
temperature – celsius (C)
amount of substance – mole (mol)
luminous intensity – candela (cd)
Derived Units in the Metric
System
A. A derived unit is a combination of
base units, and sometimes other
derived units
1. Volume: Liter (L)
a) 1 L = 1000ml = 1000 cm3
2. Density: grams per cubic centimeter (
g/cm3 )
3. Force: Newton (N) = 1 kg m/s2
4. Energy: joule (J) = 1Nm
Using Measuring Tools in Science
A. You must always read the scales on
equipment one place past the last
mark.
Examples
A. What is the volume of the following
liquids.
A. Determine the mass of the object on
the balance.
Measuring Matter
Mass
1. Measurement of the quantity of matter in an
object
2. Ex) golf ball = mass = 45 g, tennis ball = 2.5 g
Density
1. Mass and volume can be used to find density
2. D = m/v
3. Ex) mass = 10 g volume = 2 cm3
10 g = 5 g/cm3
2 cm3
Measuring Distance
Length
1. Distance between two points
2. Ex) diameter of a hair, distance from Earth to
the Moon
3. SI unit length = meter (m)
4. The unit for measure depends on what you are
measuring
a) Ex) cm – pencil m – classroom
km –
school to home
b) By choosing appropriate units you avoid large
digit numbers
Measuring Volume
Volume
1. amount of space occupied by an object
2. v = l x w x h
a) Multiply 3 numbers and units together
b) Ex) a cube 3 cm length, 3 cm width, 3 cm height
i.
3 cm x 3 cm x 3 cm = 9 cm3
Liquid volume
1. Can’t actually measure size of water but
measure the container it is in
2. Liquid volume units = liter (L) or milliliter
(mL)
Measuring Time and Temperature
Time – interval between 2 events
1. SI unit – (s) seconds
Temperature – a measure of how hot or cold
something is (thermal energy)
1. Celsius (oC)
– body temp – 37oC room temp – 20oC
freezing point – 0oC
boiling – 100oC
1. Kelvin (K) – 0 K is coldest possible
temperature
freezing point – 273 K boils – 373 K
oC
= K – 273
K = oC + 273
Converting within the metric
system
A. Although the basic units are
sufficient for most measurements,
many times it is necessary to talk
about amounts so big, or so little
that the numbers would be hard to
understand if they were reported in
m,g,or l.
Converting Within the Metric
System
Conversion Factor
A. Conversion factors (a ratio that is equal to
one) are used to change one unit to another
1. Ex) 1000 mL in 1 L
2. 1000 mL = 1
1L
1. 1L
=1
1000 mL
1000 mL = 1L = 1
1L
1L
kilogram (kg) --- gram (g) --- pound (lb) --- ounce (oz) --- meters (m)
miles (mi) --- centimeters (cm) --- feet (ft) --- gallon (ga) --- liters (L)
inch (in) --- second (s) --- minute (min) --- hour (hr) --- milliliter (mL)
kilometer (km) --- day (day) --- fluid ounce (fl oz)
1 mile = 5,280 feet --- 1,600 meters = 1 mile --- 1 pound = 16 ounces
1 kilogram = 2.2 pounds --- 1 inch = 2.54 centimeters --- 1 ounce =
28.35 grams
1 gallon = 3.79 liters --- 128 fluid ounces = 1 gallon
1,000 grams = 1 kilogram
1,000 milliliters = 1 liter --- 1,000 meters = 1 kilometer
Understanding size in metric
conversions
A. Which is larger 1m or 1cm?
B. Which is smaller 1km or 1dm?
Practice Converting Units
A. Convert 1m to cm.
A. How many grams are in 1.25 kg?
A. Convert 345.6 l to microliters.
Combining Skills
A. Which is bigger 1m or 100mm?
B. Which is smaller 3.25km of 3,250m?
Converting Using Dimensional
Analysis
A. Many times it is necessary to convert
from one unit to another using an
equality:
1. Equations
a) Ex: Converting Celsius to Fahrenheit
2. Fractional
a) Converting Metric to English
Examples
A. Convert 356.7 cm to inches
A. Convert 12.8m to inches
A. Convert 7 weeks into seconds