Module 2 For Beed 1: Guihulngan City Campus, Negros Oriental, Philippines Science Departmen
Module 2 For Beed 1: Guihulngan City Campus, Negros Oriental, Philippines Science Departmen
Module 2 For Beed 1: Guihulngan City Campus, Negros Oriental, Philippines Science Departmen
COURSE OUTLINE
Timeframe (Wk)
Topic
st
1 wk NOrSU Preliminaries
2nd & 3rd wk Module 1: Lesson 1:
4th & 5th wk Lesson 2:
6th & 7th wk Module 2: Lesson 3: SI Units
8th & 9th wk Lesson 4: Conversion Factors
10th wk MIDTERM EXAM
NOTE: Please be reminded that the Course Outline is designed to fit the Online/Modular
classes and not everything from the Course Syllabus may be covered throughout the
semester due to the pandemic.
Introduction
Measurements provide the macroscopic information that is the basis of most of the
hypotheses, theories, and laws that describe the behavior of matter and energy in both the
macroscopic and microscopic domains of chemistry. Every measurement provides three kinds of
information: the size or magnitude of the measurement (a number); a standard of comparison for
the measurement (a unit); and an indication of the uncertainty of the measurement. While the
number and unit are explicitly represented when a quantity is written, the uncertainty is an aspect
of the measurement result that is more implicitly represented and will be discussed later.
Measurements provide quantitative information that is critical in studying and practicing
chemistry. Each measurement has an amount, a unit for comparison, and an uncertainty.
Measurements can be represented in either decimal or scientific notation. Scientists primarily use
the SI (International System) or metric systems. We use base SI units such as meters, seconds,
and kilograms, as well as derived units, such as liters (for volume) and g/cm 3 (for density). In
many cases, we find it convenient to use unit prefixes that yield fractional and multiple units,
such as microseconds (10−6 seconds) and megahertz (106 hertz), respectively.
Motivation/Prompting Questions
In the sciences, there must be standard methods for describing the size, mass,
temperature, and other characteristics of any material. For centuries, the metric system, with its
decimal structure, was the basis for scientific measurements and, in most countries, for everyday
use as well. However, few countries still retained the English system of weights and measures
for all purposes except scientific work. Whereas the metric system is purposefully designed to
provide for clear definitions and easy calculations, the English system is simply a collection of
measurements and units that grew up over many years.
Discussion
Measurement
- heart of modern science;
- it makes identification of substances more precise and enable more scientific
generalities to be made.
- the number in the measurement can be represented in different ways, including
decimal form and scientific notation. (Scientific notation is also known as exponential
notation.) For example, the maximum takeoff weight of a Boeing 777-200ER airliner
is 298,000 kilograms, which can also be written as 2.98 × 10 5 kg. The mass of the
average mosquito is about 0.0000025 kilograms, which can be written as 2.5 ×
10−6 kg.
- Units, such as liters, pounds, and centimeters, are standards of comparison for
measurements. When we buy a 2-liter bottle of a soft drink, we expect that the
volume of the drink was measured, so it is two times larger than the volume that
everyone agrees to be 1 liter. The meat used to prepare a 0.25-pound hamburger is
measured so it weighs one-fourth as much as 1 pound. Without units, a number can
be meaningless, confusing, or possibly life threatening. Suppose a doctor prescribes
phenobarbital to control a patient’s seizures and states a dosage of ―100‖ without
specifying units. Not only will this be confusing to the medical professional giving
the dose, but the consequences can be dire: 100 mg given three times per day can be
effective as an anticonvulsant, but a single dose of 100 g is more than 10 times the
lethal amount.
- has two parts: the magnitude and the unit.
SI Units
- International System of Units or SI Units (from the French, Le Système International
d’Unités)
- the more modern counterpart of metric system
- designed to make calculations as easy as possible
- have been used by the United States National Institute of Standards and Technology
(NIST) since 1964
Sometimes we use units that are fractions or multiples of a base unit. Ice cream is sold in
quarts (a familiar, non-SI base unit), pints (0.5 quart), or gallons (4 quarts). We also use fractions
or multiples of units in the SI system, but these fractions or multiples are always powers of 10.
Fractional or multiple SI units are named using a prefix and the name of the base unit. For
example, a length of 1000 meters is also called a kilometer because the prefix kilo means ―one
thousand,‖ which in scientific notation is 10 3 (1 kilometer = 1000 m = 103 m). The prefixes used
and the powers to which 10 are raised are listed in Table 2.
Length
- The standard unit of length in both the SI and original metric systems is the meter
(m). A meter was originally specified as 1/10,000,000 of the distance from the North
Pole to the equator. It is now defined as the distance light in a vacuum travels in
1/299,792,458 of a second. A meter is about 3 inches longer than a yard (Fig.1); one
meter is about 39.37 inches or 1.094 yards. Longer distances are often reported in
kilometers (1 km = 1000 m = 103 m), whereas shorter distances can be reported in
centimeters (1 cm = 0.01 m = 10−2 m) or millimeters (1 mm = 0.001 m = 10−3 m).
Temperature
- Temperature is an intensive property. The SI unit of temperature is the kelvin (K).
The IUPAC convention is to use kelvin (all lowercase) for the word, K (uppercase)
for the unit symbol, and neither the word ―degree‖ nor the degree symbol (°). The
degree Celsius (°C) is also allowed in the SI system, with both the word ―degree‖ and
the degree symbol used for Celsius measurements. Celsius degrees are the same
magnitude as those of kelvin, but the two scales place their zeros in different places.
Water freezes at 273.15 K (0 °C) and boils at 373.15 K (100 °C) by definition, and
normal human body temperature is approximately 310 K (37 °C). The conversion
between these two units and the Fahrenheit scale will be discussed later in this
chapter.
Time
- The SI base unit of time is the second (s). Small and large time intervals can be
expressed with the appropriate prefixes; for example, 3 microseconds = 0.000003 s =
3 × 10–6 and 5 megaseconds = 5,000,000 s = 5 × 106 s. Alternatively, hours, days, and
years can be used.
Derived SI Units
- We can derive many units from the seven SI base units. For example, we can use the
base unit of length to define a unit of volume, and the base units of mass and length to
define a unit of density.
Volume
- Volume is the measure of the amount of space occupied by an object. The standard SI
unit of volume is defined by the base unit of length (Figure 3). The standard volume
is a cubic meter (m3), a cube with an edge length of exactly one meter. To dispense a
Density
- We use the mass and volume of a substance to determine its density. Thus, the units
of density are defined by the base units of mass and length.
- The density of a substance is the ratio of the mass of a sample of the substance to its
volume. The SI unit for density is the kilogram per cubic meter (kg/m 3). For many
situations, however, this as an inconvenient unit, and we often use grams per cubic
centimeter (g/cm3) for the densities of solids and liquids, and grams per liter (g/L) for
gases. Although there are exceptions, most liquids and solids have densities that range
from about 0.7 g/cm3 (the density of gasoline) to 19 g/cm3 (the density of gold). The
density of air is about 1.2 g/L. Table 3 shows the densities of some common
substances.
Activity 1.2
1. Give the name and symbol of the prefixes used with SI units to indicate multiplication by
the following exact quantities.
a. 103
b. 10−2
c. 0.1
d. 10−3
e. 1,000,000
f. 0.000001
2. Give the name of the prefix and the quantity indicated by the following symbols that are
used with SI base units.
a. c
b. d
c. G
d. k
e. m
f. n
g. p
h. T
1. Indicate the SI base units or derived units that are appropriate for the following measurements:
a. the length of a marathon race (26 miles 385 yards)
b. the mass of an automobile
c. the volume of a swimming pool
d. the speed of an airplane
e. the density of gold
f. the area of a football field
g. the maximum temperature at the South Pole on April 1, 1913
2. Indicate the SI base units or derived units that are appropriate for the following measurements:
a. the mass of the moon
b. the distance from Guihulngan City to Dumaguete City
c. the speed of sound
d. the density of air
e. the temperature at which alcohol boils
f. the area of the town of Vallehermoso, Negros Oriental.
g. the volume of a flu shot or a measles vaccination
Motivation/Prompting Questions
It is often the case that a quantity of interest may not be easy (or even possible) to
measure directly but instead must be calculated from other directly measured properties and
appropriate mathematical relationships. For example, consider measuring the average speed of
an athlete running sprints. This is typically accomplished by measuring the time required for the
athlete to run from the starting line to the finish line, and the distance between these two lines,
and then computing speed from the equation that relates these three properties:
velocity = distance/time
Discussion
An Olympic-quality sprinter can run 100 m in approximately 10 s, corresponding to an
average velocity of 100 m10 s=10 m/s100 m10 s=10 m/s.
Note that this simple arithmetic involves dividing the numbers of each measured quantity
to yield the number of the computed quantity (100/10 = 10) and likewise dividing the units of
each measured quantity to yield the unit of the computed quantity (m/s = m/s). Now, consider
using this same relation to predict the time required for a person running at this speed to travel a
distance of 25 m. The same relation between the three properties is used, but in this case, the two
quantities provided are a velocity (10 m/s) and a distance (25 m). To yield the sought property,
time, the equation must be rearranged appropriately:
time = distance * velocity
The time can then be computed as 25 m10 m/s=2.5 s25 m10 m/s=2.5 s. Again, arithmetic
on the numbers (25÷10=2.5)(25÷10=2.5) was accompanied by the same arithmetic on the units
(m/m/s = s) to yield the number and unit of the result, 2.5 s. Note that, just as for numbers, when
a unit is divided by an identical unit (in this case, m/m), the result is ―1‖—or, as commonly
phrased, the units ―cancel.‖
These calculations are examples of a versatile mathematical approach known
as dimensional analysis (or the factor-label method). Dimensional analysis is based on this
premise: the units of quantities must be subjected to the same mathematical operations as their
associated numbers. This method can be applied to computations ranging from simple unit
conversions to more complex, multi-step calculations involving several different quantities.
Conversion Factors and Dimensional Analysis
A ratio of two equivalent quantities expressed with different measurement units can be
used as a unit conversion factor. For example, the lengths of 2.54 cm and 1 in. are equivalent
Since this simple arithmetic involves quantities, the premise of dimensional analysis
requires that we multiply both numbers and units. The numbers of these two quantities are
multiplied to yield the number of the product quantity, 86, whereas the units are multiplied to
yield in.×cmin.in.×cmin. . Just as for numbers, a ratio of identical units is also numerically equal
to one, in.in.=1,in.in.=1, and the unit product thus simplifies to cm. (When identical units divide
to yield a factor of 1, they are said to ―cancel.‖) Using dimensional analysis, we can determine
that a unit conversion factor has been set up correctly by checking to confirm that the original
unit will cancel, and the result will contain the sought (converted) unit.
Metric Conversions
1 centimeter (cm) = 10 millimeters (mm)
1 meter (m) = 100 centimeters (cm)
1 kilometer (km) = 1000 meters (m)
Standard Conversions
1 foot (ft) = 12 inches (inch)
1 yard (yd) = 3 feet (ft)
1 yard (yd) = 36 inches (inch)
Standard Conversions
1 ounce (oz) = 16 drams (dr)
1 pound (lb) = 16 ounces (oz)
1 hundredweight (cwt) = 100 pounds (lb)
1 ton = 20 hundredweight (cwt)
1 ton = 2000 pounds (lb)
Example
Q: How many meters are in 4.300 km?
(This can be solved even in your head – by moving the decimal point in 4.300 three
places to the right. But you need to show your evidences through solutions to prove the
steps and methods to apply in deriving the correct answer.)
Solutions: 1 km = 1,000 m
4.300 km (1,000 m / 1 km) = 4,300 m
Feedback to Assessment
The result of your assessment will be announced after the submission of the module.
Checking will be done by me. Those students who are done submitting their outputs of the given
module will be recognized appropriately.
Read and study this module and answer it seriously. Make use of your Journal Notebook
for all of your answers.
Take a picture of your answers and submit it in the Comment Section only where the
instruction of this module lesson is found and posted.
Rubrics for Essay Questions adopted by: Dr. Rhonda Dubec of Lakehead University
1. Content
NOTE:
OUTPUTS FOR THIS MODULE 2 SHOULD BE SUBMITTED ON OR BEFORE
OCTOBER 26, 2021, TUESDAY, 12:00 MIDNIGHT.
NOTE:
Affix your Signature with Date Above your Printed Name at the End of the Lesson 2
Assignment, which signifies that you have completed the task for the Module 2 and
nothing else follows.
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…NMEA’21-‘22