HIGH SCHOOL SCIENCE
Practice
of Science
The
WILLMAR PUBLIC SCHOOL
2013-2014 EDITION
C HAPTER 1
Practice of
Science
In this chapter you will:
1.understand what science is and how it
obtains knowledge
2.understand how scientist conduct an
investigation
3.understand the connections between
science and technology
C HAPTER 1 S ECTION 1
What is Science?
O BJECTIVES
1. Describe how science gains knowledge.
2. Identify and describe what is studied in
science.
Vocabulary:
• science
• specialization
• life science
• Earth and space science
• physical science
Science is a way of
knowing about the
natural world. It is a
way of finding out why
things happen they
way they do.
Science uses
observations, a system of methods, and logical
reasoning to discover that knowledge. Scientists try to
solve problems by testing possible answers to see if they work.
Science knowledge is based on observations, questioning, and
testing.
As people learn more about the world, they choose more
specific subjects to study or specialize. Specialization is
studying or working in only one part of a subject. A person
who studies or works in one part of a subject is called a
specialist. How many different sciences careers can you
name? Your list would probably include doctor, engineer,
astronaut, veterinarian, and park ranger. But it could also
include bacteriologist (a person who studies bacteria),
ornithologist (a person who studies birds), seismologist (a
person who studies earthquakes), and thermodynamicist (a
person who studies the physics of heat & energy). Science
spans many diverse fields and interests.
Because the areas of scientific study are so diverse, scientists
organize their work into three major branches of study. The
three main branches of natural science are life
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science, Earth and space science, and physical
science.
NATURAL SCIENCE
Life
Science
Earth & Space
Science
Physical
Science
Botany
Geology
Physics
Ecology
Oceanography
Chemistry
Zoology
Meteorology
Genetics
Astronomy
Life science, or biology, is the study of living things. Life
scientists study how living things interact with each other and
with their surroundings. It is divided into many different
branches that includes plants, animals, and microscopic life
forms. The study of living things affects your life in many
ways. Some of the foods you eat are produced using
information about how plants grow, using knowledge of the
activities of insects, and using the knowledge of molds and
bacterias. Many plants have been genetically modified to
grow bigger and faster. Crime lab technicians work with
different kinds of evidence. Evidence may include cloth,
fibers, bits of paper, hair, skin and blood.
Earth and the processes that shape the Earth. Besides
geology, Earth and space science includes oceanography,
meteorology, and astronomy. The scientific study of the sea is
called oceanography. In order to study the ocean,
oceanographers not only study the ocean from its surface, but
also in miniature research submarines. These submarines can
go practically anywhere in the ocean. Meteorology is the study
of weather and climate. It is important to understand the
weather so you can be predict and be safe during a storm.
Astronomy is the study of space. Understanding space helps
us understand our Earth better. If we understand Mars, then
we can compare and contrast to our Earth.
The last branch of natural science is physical science.
Physical science is the study of non-living things. The two
main areas of physical science are chemistry and physics.
Chemistry is the study of the composition, structure,
properties, and reactions of matter. Physics is the study of
matter and energy and the interactions between the two
through forces and motion.
Although it is convenient to think of science as divided into
three branches, these areas are not really separate at all. Most
scientific questions being investigated today span the different
fields of science. Also, in many non-science areas, a
knowledge of science is essential in order to perform the job.
Earth and space science is the study of Earth and its place
in the universe. The foundation of Earth science is geology.
Geology is the study of the origin, history, and structure of
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Section Review:
1. How do scientists gain knowledge?
2.Why do scientist specialize?
3. What are the three branches of natural science?
4.Into which branch of science would you classify the
following: a scientist studying the organisms in a river?
5. How do the different branches of science depend on one
another?
6.How do you think a knowledge of science would benefit a
chef?
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C HAPTER 1 S ECTION 2
Scientific Method
O BJECTIVES
1. Explain the steps of the scientific method.
People have a strong sense of curiosity. Curiosity provides
problems or questions about observations that leads to
scientific inquiry. In order to solve the problem or answer the
questions about the world around them, scientists need to
gather information. An organized plan for gathering,
organizing, and communicating information is called
scientific method. The goal of the scientific method is
to solve a problem or to better understand an
observed event.
2. Compare the differences between hypothesis,
scientific theory, and scientific law.
Vocabulary:
• scientific method
• observation
• hypothesis
• variable
• independent variable
• dependent variable
• control experiment
• analyzing
• scientific theory
• scientific law
Scientific inquiry begin with observations. An observation is
information obtained through your senses. Your senses
include sight, hearing, touch, taste, and smell. Observations
can be either quantitative or qualitative. Quantitative
observations deal with a number, or amount. Qualitative
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observations deal with descriptions that cannot be expressed
in numbers.
is observed for changes, all other variables are kept constant
or controlled.
From the observations, a question or problem can be
developed. Some problems or questions cannot be
investigated by scientific inquiry. If you had a question about
why a mp3 player stopped working, that would be a scientific
questions; however, if you were wondering what kind of music
to play, that would not be a scientific question.
As the hypothesis is being tested, data is being collected. Data
is the recorded facts, figures, measurements, or other
evidence from an experiment. It is important to organize the
data into a data table. A data table helps you organize the
information you collect in an experiment so you can analyze
it. Analyzing is studying the relationship between the
variables. After all the data have been collected, they will
need to be interpreted or analyzed. One useful tool that can
help you analyze your data is a graph.
In trying to answer a question, you are in fact developing a
hypothesis. A hypothesis is a possible explanation or
proposed answer to a question. It is important to remember
that a hypothesis is not a fact. Repeatable observations are
known as facts. Instead a hypothesis is only one possible way
to explain a group of observations.
In science, a hypothesis must be testable. Scientists
perform experiments to test their hypothesis. In an
experiment, any factor that can change is called a variable.
One variable that is purposely changed to test the hypothesis,
or the variable that causes a change in another, is called the
independent variable. The variable that may change in
response to the independent variable is the dependent
variable. To examine the relationship between a
independent variable and the dependent variable, scientists
use controlled experiments. A controlled experiment is
an experiment which only one independent variable is
deliberately changed at a time. While the dependent variable
Now that you have gathered and analyzed your data, you can
draw conclusions. First you decide if your hypothesis is
supported or not. You should ask yourself whether the data
supports your hypothesis. You also need to consider whether
you collected enough data and whether anything happened
during the experiment that might have affected the results. If
your data supports the hypothesis, you should state that the
data supports the hypothesis; however, if your data does not
support your hypothesis, a new hypothesis may be created.
Data should never be revised to fit a hypothesis.
An important part of scientific inquiry is communicating your
results. Scientists share their ideas in many ways. For
example, they give talks at scientific meetings, exchange
information on the Internet, or publish articles in scientific
journals.
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As a body of knowledge, science is built up cautiously.
Scientists do not accept a new hypothesis after just one
successful experiment. Rather a hypothesis is tested
repeatedly as many different scientists try to apply it to their
own work. Once a hypothesis has been supported in repeated
experiments, scientists can begin to develop a theory. A
scientific theory is a hypothesis that has been tested again
and again by many scientists, with similar results each time.
A scientific theory is not a guess. It is the best explanation
science has to offer about a problem. Theories are never
proved, but become stronger and stronger if the facts continue
to support them. However, if an existing their fails to explain
new facts, the theory may be revised or a new theory may
replace it.
A scientific law is a statement that describes what scientists
expect to happen every time under a particular set of
conditions. Unlike a theory, a scientific law describes
an observed patter in nature without attempting to
explain it.
Section Review:
1. What is the goal of the scientific method?
2.What are the variables in a controlled experiment?
3. Every time you and your friend study for an exam while
listening to classical music, both of you do well on the
exam. What testable hypothesis can you develop from
your observations?
4.What steps of the scientific method should be done
before performing an experiment?
5. What is one way to help you analyze data?
6.Why is a scientific theory more accepted than a
hypothesis?
7. What does a scientific law describe?
8.How do scientific theories differ from scientific laws?
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C HAPTER 1 S ECTION 3
Technology & Science
When you see or hear the word technology, you may think of
things such as iPads, mp3 players, and cellphones. But
technology includes more than modern inventions. Ancient
inventions, such as stone tools, the wheel, and the compass,
are examples of technology too. Technology has been around
since people started to make things to suit their needs.
As scientific knowledge is discovered, it can be applied in
ways that improve the lives of people. Technology is the
use of knowledge to solve practical problems. While the goal
of science is to expand knowledge, the goal of technology is to
apply that knowledge and improve the way people live.
Science and technology are interdependent; advances in one
lead to advances in the other.
O BJECTIVES
1. Describe technology.
2. Explain the connections between technology
and society.
3. Describe the importance of analyze the risks
and benefits of technology.
Vocabulary:
technology
risk-benefit analysis
In every age of history, technology has had a large impact on
society, from the Stone Age thousand years ago to the
Information Age today. During the Stone Age, people used
stones to make tools. Spears, axes, and spades enabled people
to hunt animals and grow crops. During the Iron Age, people
produced iron to make weapons and tools, such as chisels,
saws, water wheels, and grain mills. Today, in the
Information Age, people use electronic devices to share
information quickly around the world.
In addition to positive effects, technology can have negative
consequences. Technological advances make many jobs
easier to perform; however, the advance in technology can
cause people to lose their jobs. In deciding whether to use a
particular technology, people must analyze its possible risks
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and benefits. The process of risk-benefit analysis involves
evaluating the possible problems, or risks, of a technology
compared to the expected advantages, or benefits. In
evaluating a technology’s risks and benefits, individuals and
societies must consider human values. A value is something
that a person or society regards as important, such as health,
honesty, convenience, and personal freedom. Difficulties can
arise when values conflict - when one value favors a
technology while another value cautions against it.
Section Review:
1. What is the goal of technology?
2.How does technology differ from science?
3. How has technology impact society?
4.List one example of technology that has increased the
pace of your life. What positives and negatives impact
has this technology had?
5. Why is it important to analyze the risks and benefits of
technology?
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C HAPTER 1 S ECTION 4
Mathematics & Science
O BJECTIVE
1. Explain how math skills help scientists analyze
their data.
Vocabulary:
• estimate
• mean
• median
• mode
• accuracy
• precision
• significant figures
• scientific notation
• percent error
You might think that mathematics as something that is
separate from science; however, it is not. Mathematics is
sometimes called the “language of science.” Mathematics is
essential for asking and answering questions about the
natural world. From making measurements to collecting and
analyzing data, scientists use math every day.
Scientists must sometimes rely on estimates when they cannot
obtain exact numbers. An estimate is an approximation of a
number based on reasonable assumptions. Estimating is not
the same as guessing because an estimate is based on known
information. Astronomers can’t actually measure the distance
between stars. Park ranges can’t count the number of trees in
large forests. Instead, scientists fond ways to make
reasonable estimates like using indirect measurements.
There are several ways to determine an “average.” They
include the mean, median, and mode. The mean is
calculated by adding up all the numbers and then dividing by
the total number of items in the list.
Mean = (Sum of Values) / (Total # of Values)
Median is the middle number of a set of data. To find the
median, place all the numbers in order from smallest to
largest. If the order list has an odd number of entries, the
median is the middle entry. If the list has an even number of
entries, you add the two middle numbers together and divide
by two. Mode is the number that appears most often in a list
of numbers.
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Both accuracy and precision are important when you make
measurements. Accuracy is the closeness of a measurement
to the actual value of what is being measured. If you think of a
target, accuracy is how close to the bull’s eye the shots are
located. Precision is how close a group of measurement are
to each other or how exact a measurement is. On the target,
precision is how close together the shots are located.
You can determine the number of significant figures in a
number using a few simple rules.
• All non-zero numbers are significant. (472 has three
significant figures, 14.75 has four significant figures)
• Zeroes between significant digits are significant. (103 has
three significant figures, 10.821 has five significant figures)
• If there is no decimal point, then trailing zeroes are not
significant. (81000 has two significant figures, 10100 has
three significant figures)
• If there is a decimal point, then all trailing zeroes are
significant. (376.90 has five significant figures, 10. has two
significant figures)
• If a number is less than one, then the first significant figure
is the first non-zero digit after the decimal point. (0.004 has
one significant figure, 0.00984 has three significant figures)
Whenever you measure something, you give meaning to each
digit in the measurement. Significant figures refer to the
digits in a measurement. Significant figures in a
measurement include all the digits that have been measured
exactly, plus one digit whose value has been estimated.
Scientist often work with very large or very small numbers.
For example, the speed of light is about 300,000,000 m/s and
the speed of an average snail is about 0.00086 m/s. Instead
of writing out all the zeros, scientists use scientific notation.
Scientific notation is a way to express numbers in terms of
a decimal number between 1 and 10 multiplied by a power of
ten. For example, the speed of light would be expressed as 3.0
x 108 and the snail speed would be expressed as 9.84 x 10-3. A
positive exponent tells the decimal is really that number
places to the right of the decimal point. A negative exponent
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tells the decimal is really that number places to the left of the
decimal point. If you were to take 9085000 and express it as
in scientific notation, first take the first integer (between 0
and 10). Add the decimal and the rest of the significant
numbers. Then add time ten to the power of the number and
direction the decimal moved. So 9085000 would be
9.085x106.
The precision of a calculated answer is limited by the
measurement with the least significant figures used in the
calculation. When you add or subtract measurements, the
answer can only have as many figures after the decimal point
as the measurement with the fewest figures after the decimal.
For example, 9.2 m + 53.41 m = 62.6 m because the
measurement 9.2 meters only has one point after the decimal.
When multiplying or dividing, you need to follow a slightly
different rule; the answer can only have the same number of
significant figures as the measurement with the fewest
significant figures. For example, 6.2 cm x 312 cm = 1900 cm2
because 6.2 cm has two significant figures.
Section Review:
1. What are estimates based on?
2.What are the three ways of calculating an “average”?
3. Why is it important to obtain measurements that are
both accurate and precise?
4.How many significant figures does 202.090 have?
5. Why do scientists use scientific notation?
6.How does the precision of measurements affect the
precision of scientific calculations?
7. What is the rule for multiplying or dividing
measurements?
Percent error calculations are used to determine how
accurate, or close to the true value, an experimental value
really is. To calculate percent error divide the difference
between the measured value and accepted value with the
accepted value then times by 100%.
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C HAPTER 1 S ECTION 5
Measurement
O BJECTIVES
1. Describe why scientists use a standard
measurement system.
2. Describe the tools used to measure length,
volume, mass, time, and temperature.
3. Identify the SI units for length, volume, mass,
time, and temperature.
Vocabulary:
• measurement
Measurement is the system of comparing an object to a
standard. The metric system includes units of length (meters),
weight or mass (grams), and volume (liter). When we make a
measurement of length, weight, or volume, we are comparing
the object against a standard (1 meter, 1 gram, 1 volume).
Tools for metric measurements provide these standards.
Using the same system of measurement minimizes confusion
among scientists all over the world.
More than 200 years ago, most countries used their own
measurement systems. In the 1790’s, scientists in France
developed a universal system of measurement called the
metric system. The metric system is a system of measurement
based on the number ten. Modern scientists use a version of
the metric system call the International System of Units,
abbreviated SI. Using SI as the standard system of
measurement allows scientists to compare data and
communicate with each other about their results.
• length
• volume
• water displacement
• mass
• weight
• time
• temperature
Length is the distance from one point to another. The metric
ruler is the tool for measuring length, and width. It looks like
any other kind of ruler but includes units of millimeters,
centimeters, and meters. The SI unit for length is the meter.
You can also determine the volume of a rectangular solid
using a ruler. Volume is the amount of space an object takes
up. Volume = length x width x height. The SI unit for volume
is the cubic meter (m3); however, in science class you will be
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using the cubic centimeter (cm3). The unit you would use is
the cubic centimeter, one cubic centimeter equals to one
milliliter.
A graduated cylinder measures volume of a liquid. It looks like
a drinking glass that has marks for volume on the side—
milliliters, centiliters, and liters.
Suppose you wanted to measure the volume of a rock.
Because of its irregular shape, you cannot measure the rock’s
length, width, or height. You would then use a graduated
cylinder and immerse the rock in water. Then you would
measure how much the water level rises, this method is called
water displacement.
The balance or scale is the appropriate tool for measuring
mass or weight in grams. Mass is how much matter is in
something. Weight is a measurement of the force of gravity
on an object. The balance looks something like a seesaw.
With the object being measured on one side, a combination of
standard weights of milligrams, centigrams, and kilograms
comprise the other half. The SI units for mass is kilogram;
however, in science class you will be using the gram. When
the weight of the object being measured equals the
combination of standard weights the scale balances.
A stopwatch or a clock with a second hand is used to measure
time. Time is the period between two events. The SI unit for
time is the second.
A thermometer is used to measure temperature.
Temperature is a measurement of the amount of heat in
something. The SI unit for temperature is the kelvin.
Scientists frequently measure temperature with Celsius scale.
A temperature of 0 kelvin (K), refers to the lowest possible
temperature that can be reached. In degrees Celsius, this
temperature is -273.15 degrees Celsius. Kelvins equal degrees
Celsius plus 273.15. On the Celsius scale, the freezing point of
water is 0 degrees and the boiling point is 100 degrees.
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Section Review:
1. Why do scientists use a standard measurement system?
2.What is the standard measurement system used by
scientists around the world?
3. Suppose that two scientists use different measurement
systems in their work. What problems might arise if they
shared their data?
4.List the SI units for length, volume, mass, time and
temperature.
5. What is the difference between weight and mass?
6.What tool should you use to measure the volume of
water?
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C HAPTER 1 S ECTION 6
Organizing Data
O BJECTIVE
1. Identify how scientists organize data.
2. Describe the uses of different graphs.
3. Understand the different types of trends shown
on a graph.
4. Calculate slope on a linear graph.
Vocabulary:
• data table
• graph
• line graph
• bar graph
• circle graph
• pictograph
• linear trend
• slope
• nonlinear trend
Scientists accumulate vast amounts of data by observing and
making measurements. Scientists organize their data by using
data tables and graphs. Data is facts, figures, and other
evidence gathered through observations. A data table
provides you with an organized way to collect and record your
observations, or data. After all your data have been collected,
they need to be interpreted. One useful tool that can help you
interpret data is graph. A graph is a visual representation of a
set of data. Think of graphs as pictures of the data. Graphs an
reveal patterns or trends in data by seeing similarities.
There are four types of graphs that are commonly used: line
graph, bar graph, circle, and pictograph.
A line graph is used for showing changes that occur in
related variables. They display data to show how the
dependent variable changes in response to the independent
variable. The horizontal axis, or x-axis, shows the range of the
independent variable. The vertical axis, or y-axis, shows the
range of the dependent variable.
A bar graph is often used to compare a set of measurements,
amounts, or changes. A bar graph is similar to a line graph
except bars rather than points show the data. In a bar graph,
the dependent variable can be shown on either the vertical or
horizontal axes.
A circle graph, or pie graph, is a divided circle that shows a
parts of a whole. The size of each section shows a percentage
of the whole circle. If you add the percentages of the sections
together, they equal 100 percent.
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A pictograph is is a graph using pictures. It can be like a
circle graph by showing parts of a whole or use symbols to
represent a number of something.
Section Review:
1. What can graphs reveal that data tables cannot?
Graphs allow you to identify trends and make predictions.
There are three trends: linear, nonlinear, and no trend.
2.What type of data can line graphs display?
A linear trend is a graph with a straight line. When a graph
is linear, you can easily see how two variables are related. If
the data yields linear trend, you can determine a value called
slope. Slope is the steepness or ratio of the vertical change to
horizontal change. Slope (m) is calculated using the formula:
4.If the rise is 16 and the run is 4, what is the slope of the
line?
3. How do you determine the slope of a line?
5. Why are graphs powerful tools in science?
6.Describe a nonlinear graph.
“Rise” represents the change in the dependent variable.
“Run” represents the change in the independent variable.
You can use a linear graph to make predictions by extending
the line.
A nonlinear trend show different trends. One nonlinear
graph the points may fall along a curve. A graph may rise
then level off or have a repeating pattern.
Lastly, data may scatter and show no recognizable pattern
which would be no trend. When there is no identifiable
trends in a graph, it most likely means that there is no
relationship between the two variables.
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C HAPTER 1 S ECTION 7
Safety in the Lab
Research in science can be exciting, but it also has potential
dangers. For example, a field scientist could collect a water
samples from a polluted lake. There are many
microorganisms in the water that could make her sick. The
water and shore are also strewn with dangerous objects such
as sharp can lids and broken glass bottles that could cause
serious injury. Whether in the field or in the lab, knowing how
to stay safe in science is important.
Lab procedures and equipment may be labeled with safety
symbols. These symbols warn of specific hazards, such as
flames or broken glass. Learn the symbols so you will
recognize the dangers. Then learn how to avoid them. Lab
safety symbols warn of specific hazards, such as flames or
broken glass. Knowing the symbols allows you to recognize
and avoid the dangers.
O BJECTIVES
1. Describe the importance of being safe in the
lab.
2. Understand how to react in an accident.
Vocabulary:
safety symbols
safe practices
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Wearing protective gear is one way to avoid many hazards in
science. For example, to avoid being burned by hot objects,
use hot mitts to protect your hands. To avoid eye hazards,
such as harsh liquids splashed into the eyes, wear safety
goggles.
Following basic safety rules is another important way to stay
safe in science. Safe practices help prevent accidents.
Several lab safety rules are listed below. Following basic safety
rules, such as wearing safety gear, helps prevent accidents in
the lab and in the field. Different rules may apply when you
work in the field. But in all cases, you should always follow
your teacher’s instructions.
Lab Safety Rules
1. Wear long sleeves and shoes that completely cover your
feet.
2. If your hair is long, tie it back or cover it with a hair net.
3. Protect your eyes, skin, and clothing by wearing safety
goggles, an apron, and gloves.
4. Use hot mitts to handle hot objects.
5. Never work in the lab alone.
9. Always add acid to water, never the other way around, and
add the acid slowly to avoid splashing.
10.Take care to avoid knocking over Bunsen burners, and
keep them away from flammable materials such as paper.
11.Use your hand to fan vapors toward your nose rather than
smelling substances directly.
12.Never point the open end of a test tube toward anyone—
including yourself!
13.Clean up any spills immediately.
14.Dispose of lab wastes according to your teacher’s
instructions.
15.Wash glassware and counters when you finish your work.
16.Wash your hands with soap and water before leaving the
lab.
Even when you follow the rules, accidents can happen.
Immediately alert your teacher if an accident occurs. Report
all accidents, whether or not you think they are serious.
All accidents should be reported immediately.
6. Never engage in horseplay in the lab.
7. Never eat or drink in the lab.
8. Never do experiments without your teacher’s approval.
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Section Review:
1. What do the safety symbols describe?
2.If you see a symbol with flames on it, what do you know
about that chemical?
3. How should you protect your skin during a lab?
4.If you are using a chemical and it spills, what should you
do?
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