Transcript Chapter 2 PPT - North Allegheny School District

Table of Contents
Chapter: Measurement
Section 1: Description and
Measurement
Section 2: SI Units
Section 3: Drawings, Tables,
and Graphs
Description and Measurement
1
Measurement
• Measurement is a way to describe the world
with numbers.
• It answers questions such as how much, how
long, or how far.
• Measurement can describe the amount of
milk in a carton, the cost of a new compact
disc, or the distance between your home and
your school.
Description and Measurement
1
Measurement
• In scientific endeavors, it is important that
scientists rely on measurements instead of
the opinions of individuals.
• You would not know how safe the
automobile is if this researcher turned in
a report that said, “Vehicle did fairly well
in head-on collision when traveling at a
moderate speed.”
Description and Measurement
1
Describing Events
• Measurement also can describe events.
• In the 1956 summer Olympics, sprinter Betty
Cuthbert of
Australia came
in first in the
women’s 200-m
dash.
Description and Measurement
1
Describing Events
• She ran the race in 23.4 s.
• Measurements convey information about the
year of the race,
its length, the
finishing order,
and the time.
Description and Measurement
1
Estimation
• Estimation can help you make a rough
measurement of an object.
• Estimation is a skill based on previous
experience and is useful when you are in a
hurry and exact numbers are not required.
Description and Measurement
1
Estimation
• In many instances, estimation is used on
a daily basis.
• For example, a caterer prepares for each
night’s crowd based on an estimation of
how many will order each entrée.
Description and Measurement
1
Using Estimation
• You can use comparisons to estimate
measurements.
• When you estimate, you often use the
word about.
• For example, doorknobs are about 1 m
above the floor, a sack of flour has a
mass of about 2 kg, and you can walk
about 5 km in an hour.
Description and Measurement
1
Using Estimation
• Estimation also is used to check that an
answer is reasonable. Suppose you calculate
your friend’s running speed as 47 m/s.
• Can your friend really run a 50-m dash in
1 s? Estimation tells you that 47 m/s is
unrealistically fast and you need to check
your work.
Description and Measurement
1
Precision and Accuracy
• Precision is a description of how close
measurements are to each other.
• Suppose you measure the distance between
your home and your school five times and
determine the distance to be 2.7 km.
Description and Measurement
1
Precision and Accuracy
• Suppose a friend measured 2.7 km on two
days, 2.8 km on two days, and 2.6 km on the
fifth day.
• Because your measurements were closer to
each other than your friend’s measurements,
yours were more precise.
Description and Measurement
1
Precision and Accuracy
• The term precision also is used when
discussing the number of decimal places
a measuring device can measure.
• A clock with a
second hand is
considered
more precise
than one with
only an hour
hand.
Description and Measurement
1
Degrees of Precision
• The timing for events has become more
precise over the years.
• Events that were measured in tenths of a
second 100 years ago are measured to the
hundredth of a second today.
Description and Measurement
1
Accuracy
• When you compare a measurement to the
real, actual, or accepted value, you are
describing accuracy.
• A watch with a second hand is more precise
than one with only an hour hand, but if it is
not properly set, the
readings could be off
by an hour or more.
Therefore, the watch
is not accurate.
Description and Measurement
1
Rounding a Measurement
• Suppose you need to measure the length of
the sidewalk outside your school.
• If you found that the length was 135.841 m,
you could round off that number to the
nearest tenth of meter and still be
considered accurate.
Description and Measurement
1
Rounding a Measurement
• To round a given value, follow these steps:
1. Look at the digit to the right of the place
being rounded to.
• If the digit to the right is 0, 1, 2, 3, or
4, the digit being rounded to remains
the same.
• If the digit to the right is 5, 6, 7, 8, or
9, the digit being rounded to increases
by one.
Description and Measurement
1
Rounding a Measurement
2. The digits to the right of the digit being
rounded to are deleted if they are also to
the right of a decimal. If they are to the
left of a decimal, they are changed to
zeros.
Description and Measurement
1
Precision and Number of Digits
• Suppose you want to divide a
2-L bottle of soft drink
equally among seven people.
• Will you measure exactly
0.285 714 285 L for each
person?
• No. All you need to know is
that each person gets about 0.3
L of soft drink.
Description and Measurement
1
Using Precision and
Significant Digits
• The number of digits that truly reflect the
precision of a number are called the
significant digits or significant figures.
• Digits other than zero are always significant.
• Final zeros after a decimal point (6.545 600 g)
are significant.
• Zeros between any other digits (507.0301 g) are
significant.
• Initial zeros (0.000 2030 g) are NOT significant.
Description and Measurement
1
Using Precision and
Significant Digits
• Zeros in a whole number (1650) may or may
not be significant.
• A number obtained by counting instead of
measuring, such as the number of people in a
room or the number of meters in a kilometer,
has infinite significant figures.
Description and Measurement
1
Following the Rules
• For multiplication and division, you
determine the number of significant digits
in each number in your problem. The
significant digits of your answer are
determined by the number with fewer digits.
Description and Measurement
1
Following the Rules
• For addition and subtraction, you determine
the place value of each number in your
problem. The significant digits of the
answer are determined by the number that
is least precise.
Section Check
1
Question 1
How many oranges can fit inside a given crate?
How much rain fell on your town during the last
thunderstorm? These are questions of _______.
Section Check
1
Answer
The answer is measurement. Measurement is
used to answer questions such as: How long?
How many? How far?
Section Check
1
Question 2
It isn’t always necessary to know exactly
how much or exactly how fast. As a rough
way of looking at your data, you can use
_______.
A. assignation
B. estimation
C. pagination
D. salination
Section Check
1
Answer
The answer is B. You can use estimation to get
a rough measurement of an object.
Section Check
1
Question 3
Round 1.77 g to the nearest tenth of a gram.
Answer
The answer is 1.8 grams. The digit in the
hundreds column is above 5, so you round
up the digit in the tens column.
SI Units
2
The International System
• To avoid confusion,
scientists established
the International
System of Units, or
SI, in 1960 as the
accepted system for
measurement.
SI Units
2
The International System
• The SI units are related by
multiples of ten.
• Any SI unit can be converted
to a smaller or larger SI unit
by multiplying by a power of
10.
• The new unit is renamed by
changing the prefix.
SI Units
2
The International System
SI Units
2
Length
• Length is defined as the distance between two
points.
• The meter (m)
is the SI unit of
length. One
meter is about
the length of a
baseball bat.
SI Units
2
Length
• Smaller objects can be measured in
centimeters (cm) or millimeters (mm). The
length of your
textbook or
pencil would
be measured in
centimeters.
SI Units
2
A Long Way
• To measure long distances, you use
kilometers.
• Kilometers might be most familiar to you as
the distance traveled in a car or the measure
of a long-distance race.
• The course of a marathon is measured
carefully so that the competitors run 42.2 km.
• When you drive from New York to Los
Angeles, you cover 4,501 km.
SI Units
2
Volume
• The amount of space an object occupies is
its volume. The cubic meter (m3) is the
SI unit of volume.
SI Units
2
Volume
• To find the volume of a square or rectangular
object, such as a brick or your textbook,
measure its length, width, and height and
multiply them together.
SI Units
2
Volume by Immersion
• Not all objects have an even, regular shape.
• When you measure the volume of an
irregular object, you start with a known
volume of water and drop in, or immerse,
the object.
• The increase in the volume of water is equal
to the volume of the object.
SI Units
2
Mass
• The mass of an object measures the amount
of matter in the object.
• The kilogram (kg) is the SI unit for mass.
• You can determine mass with a triplebeam balance.
• The balance compares an object to a known
mass. Weight and mass are not the same.
Mass depends only on the amount of matter
in an object.
SI Units
2
Weight
• Weight is a measurement of force.
• The SI unit for weight is the Newton (N).
• Weight depends on gravity, which can
change depending on where the object is
located.
SI Units
2
Weight
• If you were to travel to other planets, your
weight would change, even though you would
still be the same size and have the same mass.
• This is because
gravitational
force is different
on each planet.
SI Units
2
Temperature
• The physical property of temperature is
related to how hot or cold an object is.
• Temperature is a measure of the kinetic
energy, or energy of motion, of the
particles that make up matter.
• Temperature is measured in SI with the
Kelvin (K) scale.
SI Units
2
Temperature
• The Fahrenheit and Celsius temperature scales
are the two most common scales used on
thermometers and in classroom laboratories.
• The Kelvin scale starts at
0 K. In theory, 0 K is the
coldest temperature
possible in nature.
SI Units
2
•
•
•
•
Time and Rates
Time is the interval between two events.
The SI unit of time is the second (s).
Time also is measured in hours (h).
A rate is the amount of change of one
measurement in a given amount of time.
• One rate you are familiar with is speed,
which is the distance traveled in a
given time.
Section Check
2
Question 1
If everyone used a different standard of
measurement, there would be no way to know
how one scientist’s data compared with another
scientist’s data. Instead, scientists all use an
agreed-upon standard of measurement known
as _______.
Section Check
2
A. English standard of measurement
B. European standard of measurement
C. International system of units
D. North American system of units
Section Check
2
Answer
The correct answer is C. “SI” is the
International System of Units.
Section Check
2
Question 2
If you were measuring a particular mass, for
example, a big lump of cookie dough, you
would measure it in terms of _______.
A. kilograms
B. liters
C. newtons
D. watts
Section Check
2
Answer
The answer is A.
A kilogram is a
unit of mass.
Section Check
2
Question 3
A spring scale can show you how much a
baseball mitt weighs, but why might this figure
change if you were to weigh the same object
on Mars?
Section Check
2
Answer
Gravitational pull is different on different
planets. The mass of the mitt stays the same no
matter where it is, but its weight can change.
Drawings, Tables, and Graphs
3
Scientific Illustrations
• Photographs and drawings model and
illustrate ideas and sometimes make new
information clearer than written text can.
• For example, a drawing of an airplane
engine shows how all the parts fit
together much better than several pages
of text could describe it.
Drawings, Tables, and Graphs
3
Drawings
• A drawing is sometimes the best choice to
show details.
• A drawing can emphasize only the things that
are necessary to show.
• A drawing also can show things you can’t see.
• For example, you could draw the outline of
two continents to show how they might have
fit together at one time.
Drawings, Tables, and Graphs
3
Drawings
• Drawings can show hidden things, as well.
For example, a drawing can show the details
of the water cycle.
Drawings, Tables, and Graphs
3
Drawings
Drawings, Tables, and Graphs
3
Photographs
• A still photograph shows an object exactly
as it is at a single moment in time.
• Movies show how an object moves and
can be slowed down or sped up to show
interesting features.
Drawings, Tables, and Graphs
3
Tables and Graphs
• A table displays information
in rows and columns so that it
is easier to read and
understand.
Drawings, Tables, and Graphs
3
Tables and Graphs
• A graph is used to collect, organize, and
summarize data in a visual way.
• Three common types of graphs are line, bar,
and circle graphs.
• A line graph shows the relationship between
two variables.
• A variable is something that can change, or
vary, such as the temperature of a liquid or
the number of people in a race.
• Both variables in a line graph must be numbers.
Drawings, Tables, and Graphs
3
Tables and Graphs
• One variable is shown on the horizontal axis,
or x-axis, of the graph.
• The other variable is
placed along the
vertical axis, or y-axis.
• A line on the graph
shows the
relationship between
the two variables.
Drawings, Tables, and Graphs
3
Bar Graph
• A bar graph uses rectangular blocks, or bars,
of varying sizes to show the relationships
among variables.
Drawings, Tables, and Graphs
3
Bar Graph
• One variable is divided into parts.
• The second variable must be a number.
• The bars show the size of the second variable.
Drawings, Tables, and Graphs
3
Circle Graph
• A circle graph shows the parts of a whole.
• Circle graphs are
sometimes called
pie graphs.
• Each piece of pie
visually represents
a fraction of the
total.
Drawings, Tables, and Graphs
3
Circle Graph
• A circle has a total of 360°. To make a circle
graph, you need to determine what fraction of
360 each part should be.
Drawings, Tables, and Graphs
3
Reading Graphs
• When you are using or making graphs to
display data, be careful—the scale of a graph
can be misleading.
• A broken scale can be used to highlight
small but significant changes, just as an inset
on a map draws attention to a small area of a
larger map.
• Always analyze the measurements and graphs
that you come across. If there is a surprising
result, look closer at the scale.
Drawings, Tables, and Graphs
3
Reading Graphs
• This graph does not start at zero, which
makes it appear that the number of species
has more that quadrupled from 1996-2002.
Drawings, Tables, and Graphs
3
Reading Graphs
• The actual increase is about 20 percent, as
you can see from this full graph. The broken
scale must be noted in order to interpret the
results correctly.
Section Check
3
Question 1
Suppose you have two variables, for example,
how much salt you eat in a day and how much
water you drink, and you want to visually
depict their relationship across time. What
visual tool might you use to show this
relationship?
Section Check
3
Answer
A line graph shows the relationship between
two variables. Line graphs are excellent ways
to quickly see the
relationship between a
variable plotted on the X
axis and one plotted on
the Y axis.
Section Check
3
Question 2
When you put numerical data into rows and
columns, you are creating a _______.
A. calculation
B. graph
C. table
D. waveform
Section Check
3
Answer
The answer is C. Rows and columns of
numbers make up a table.
Section Check
3
Question 3
Suppose you want to visually demonstrate how
much of a given area is woodland, how much
is grassy but has no trees, and how much has
been developed. With different segments like
this to consider, how might you choose to show
the relationship of parts to the whole?
Section Check
3
Answer
Use a circle chart. A circle chart, or “pie chart,”
is ideal for visually demonstrating how the
different segments go together to form the
whole.
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