• When you hear or read about advancements in science, do you wonder how they were made?
How did the scientists make their discoveries? Were they just lucky? Maybe, but chances are that it was much more than luck.
The scientific method probably had a lot to do with it!

• The scientific method is a series of steps that scientists use to answer questions and solve problems. The chart below shows the steps that are commonly used in the scientific method.
Although the scientific method has several distinct steps, it is not a rigid procedure whose steps must be followed in a certain order.
Scientists may use the steps in a different order, skip steps, or repeat steps.
It all depends on what works best to answer the question.

• Scientists approach problems from a variety of viewpoints. They conduct their research using available tools, data, time and people. Research often leads to new problems and new hypotheses, which require further research and testing.

• Asking a question helps you focus your investigation and identify what you want to find out. Usually, scientists ask a question after they’ve made a lot of observations.
• An observation is any use of the senses to gather information. Measurements are observations that are made with instruments.

• In 1864 and 1865, James Clerk Maxwell made observations about electricity and certain observations about magnetism and showed how the two phenomena are related. As a result of his investigations, he developed his theory of electromagnetism, one of the most important scientific advances of the nineteenth century.

Q: Why is a science lesson like a worm in a cornfield?
A: They both go in one ear and out the other.

Just because a hypothesis is untestable does not mean that it is wrong. It just means that there is no way to support or not support it.
Scientists must always formulate hypotheses for which they can make observations and gather information.

• Once you’ve asked your question, your next step is forming a hypothesis.
A hypothesis is a possible explanation or answer to a question. You can use what you already know and any observations that you have made to form the hypothesis. A good hypothesis is testable.
If no observations or information can be gathered or if no experiment can be designed to test the hypothesis, it is untestable.

• They often make a prediction that state what they think will happen during the actual test of the hypothesis.
Scientists usually state predictions in an “ If…then…” format.

1. How do scientists and engineers use the scientific method?
Scientists use the scientific method to answer questions and solve problems.
Engineers can use the scientific method to create new technology.

2. Give three examples of technology from your everyday life.
Sample answers: car engines, CD players, air-conditioning units, spoons, and doorknobs.

3.
Analyzing Methods . Explain how the accuracy of your observations might affect how you develop a hypothesis.
Sample answer: If observations or measurement are not accurate, they can affect how reasonable a hypothesis is.
As a result, answering the question may be more difficult and take more time than if observations and measurements were accurate from the beginning.

• After you form a hypothesis, you must test it to determine whether it is a reasonable answer to your question.
In other words, testing helps you find out if your hypothesis is pointing you in the right direction or if it is way off the mark. Often a scientists will test a hypothesis by testing a prediction.

• One way to test a hypothesis is to conduct a controlled experiment.
In a controlled experiment , there is a control group and an experimental group.
Both groups are the same except for one factor in the experimental group, called a variable.
The experiment will then determine the effect of the variable.

• Sometimes a controlled experiment is not possible. Stars, for example, are too far away to be used in an experiment.
In such cases, you can test your hypothesis by making additional observations or by conducting research. If your investigation involves creating technology to solve a problem, you can make or build what you want to test and see if it does what you expected it to do.

Data

• After you collect and record your data, you must analyze them to determine whether the results of your test support the hypothesis.
Sometimes doing calculations can help you learn more about your results.
Organizing numerical data into tables and graphs make relationships between information easier to see.

• Experiments don’t always turn out as expected. In 1856, William Henry Perkins was experimenting to synthesize the antimalarial drug quinine from coal tar.
He didn’t succeed, but he accidentally made aniline purple (mauve), the first synthetic dye. Mauve dye was used to color cotton, wool, and silk. Further experiments led to the development of many other dyes from coal tar.

• At the end of an investigation, you must draw a conclusion.
You could conclude that your results supported your hypothesis, that your results did not support your hypothesis, or that you need more information.
If you conclude that your results support your hypothesis, you can ask further questions.
If you conclude that your results do not support your hypothesis, you should check your results or calculations for errors.

• You may have to modify your hypothesis or form a new one and conduct another investigation. If you find that your results neither support nor disprove you hypothesis, you may need to gather more information, test your hypothesis again, or redesign the procedure.

• One of the most important steps in any investigation is to communicate your results. You can write a scientific paper, make a presentation, or create a Web site.
Telling others what you have learned is how science keeps going. Other scientists can conduct their own tests, modify your tests to learn something more specific, or study a new problem based on your results.

• Not all scientists use the same scientific method, nor do they always follow the same steps in the same order. Why not?
Sometimes you may have a clear idea about the question you want to answer.
Other times, you may have to revise your hypothesis and test it again.
While you should always take accurate measurements and record data correctly, you don’t always have to follow the scientific method in a certain order.

• Using the scientific method is a way to find answers to questions and solutions to problems.
But you should understand that answers are very rarely final answers.
As our understanding of science grows, our understanding of the world around us changes.
New ideas and new experiments teach us new things.

• Sometimes, however, an idea is supported again and again by many experiments and tests.
When this happens, the idea can become a theory or even a law.

• You’ve probably heard a detective on a TV show say, “I’ve got a theory about who committed a crime.
” Does the detective have a scientific theory?
Probably not; it might be just a guess.
A scientific theory is more complex than a simple guess.

• In science, a theory is a unifying explanation for a broad range of hypotheses and observations that have been supported by testing. A theory not only can explain an observation you’ve made but also can predict an observation you might make in the future.
Keep in mind that theories can be changed or replaced as new observations are made or as new hypotheses are tested.

• What do you think of when you hear the word law ? Traffic laws? Federal laws?
Well, scientific laws are not like these laws.
Scientific laws are determined by nature, and you

• In science, a law is a summary of many experimental results and observations. A law tells you how things work. Laws are not the same as theories because laws only tell you what happens, not why it happens. Although a law does not explain why something happens, the law tells you that you can expect the same thing to happen every time.

QUIZ
1. What is the relationship between an experiment and a hypothesis?
2.
When following the scientific method, what is the correct procedure for investigation?
3. What is a variable?

1. An experiment is a test of a hypothesis to support or disprove it.
2. There is no correct order as long as steps are followed so that accurate measurements are made and data is recorded.
3. A factor that can be changed in an experiment to determine its effect on the outcome.

Are the following laws or theories:
1. An object that is dropped falls to the ground.
2. Gravitational forces causes an attraction between two objects.
3. The universe began with a very powerful explosion.
1. ( law )
3. ( theory )
2. ( law )

• A model is a representation of an object or system. Models are used in science to describe or explain certain characteristics of things.
Models can also be used for making predictions and explaining observations. A model is never exactly like the real object or system —if it were, it would no longer be a model.
Models are particularly useful in physical science because many characteristics of matter and energy can be either hard to see or difficult to understand.

• When you’re trying to learn about something that you can’t see or observe directly, a model can help you visualize it, or picture it in your mind.
Familiar objects or ideas can help you understand something a little less familiar.

• Models not only can represent scientific ideas and objects but also can be tools that you can use to conduct investigations and illustrate theories.

• When creating technology, scientists often create a model first so that they can test its characteristics and improve its design before building the real thing.

• Models allow you to test ideas without having to spend the time and money necessary to make the real thing.

1. What is the purpose of a model?
2. Give three examples of models that you see every day.
3. Interpreting Models.
Both a globe and a flat world map model show certain features of the Earth. Give an example of when you would use a globe and an example of when you would use a flat map.

1. The purpose of a model is to represent concepts or characteristics of objects that are more difficult to see or hard to explain.
2. Acceptable answers include bus maps, and attendance record, a stuffed animal, assembly instructions for a bicycle, and sheet music.
3. Sample answers: A globe would be better if you wanted to compare the sizes of different countries; a flat map would be better if your wanted to carry a world map in you backpack.

• Hundreds of years ago, different countries used different systems of measurement.
In England, the standard for an inch used to be three grains of barley placed end to end.
Other standardized units of the modern English system, which is used in the United States, was based on parts of the body, such as the foot.
Such units were not very accurate because they were based on objects that varied in size.

• Eventually people recognized that there was a need for a single measurement system that was simple and accurate. In the late 1700 ’s, the
French Academy of Sciences began to develop a global measurement system, now known as the
International System of Units, or SI.

The International System of Units
• Today most scientists in almost all countries use the International System of
Units.
One advantage of using SI measurements is that it helps scientists share and compare their observations and results. Another advantage of SI is that all units are based on the number 10 , which makes conversions from one unit to another easier to do.
The table in the appendix of your book contains the commonly used SI for length, volume, mass, and temperature.

• How long is an Olympic-sized swimming pool?
To describe its length, a physical scientist would use meters (m), the basic SI unit of length.
Other SI units of length are larger or smaller than the meter by multiples of 10.

• For example, 1 kilometer (km) equals
1,000 meters. If you divide 1 m into 1,000 parts, each part equals 1 mm. This means that 1 mm is one-thousandth of a meter.
Although that seems pretty small, some objects are so tiny that even smaller units must be used. To describe the length of a grain of salt, micrometers (um) or nanometers (nm) are used.

• Imagine that you need to move some lenses to a laser laboratory.
How many lenses will fit into a crate? That depends on the volume of the crate and the volume of each lens.
Volume is the amount of space that something occupies.

• Volumes of liquid are expressed in liters (L).
Liters are based on the meter. A cubic meter (1 m 3 )is equal to 1,000 L. So 1,000 L will fit into a box 1 m on each side.
A milliliter
(mL) will fit into a box 1 cm on each side. So 1 mL = 1 cm 3 . Graduated cylinders are used to measure the volume of liquids.

• Volumes of solid objects are expressed in cubic meters (m 3 ).
Volumes of smaller objects can be expressed with cubic centimeters (cm 3 ) or cubic millimeters
(mm 3 ). To find the volume of a crate, or any other rectangular shape, multiply the length by the width by the height. To find the volume of an irregularly shaped object, measure how much liquid that object displaces.

• How many cars can a bridge support?
That depends on the strength of the bridge and the mass of the car.
Mass is the amount of matter that something is made of. The gram (g) is the basic SI unit for mass and would be used to express the mass of a car. Grams (one-thousandth of a kilogram) are used to express the mass of small objects.
A medium-sized apple has a mass of about 100g.
Masses of very large objects are expressed in Metric tons. A metric ton equals 1,000 kg.

• How hot is melted iron?
To answer this question, a physical scientist would measure the temperature of the liquid metal.
Temperature is a measure of how hot (or cold) something is.
You are probably used to expressing temperature with degrees Fahrenheit ( 0 F).
Scientists often use degree Celsius ( 0 C), but the kelvin (K) is the SI unit for temperature.
The temperature conversion table in the book compares 0 F with 0 C, the unit you will most often see in this book.

• Some quantities are formed from combinations of other measurements.
Such quantities are called derived quantities.
Both area and density are derived quantities.

• How much carpet would cover the floor of your classroom? It depends on the area of the floor.
Area is a measure of how much surface an object has. To calculate the area of a rectangular surface, measure the length and width, then use this equation:
Area = length x width
The units for area are called square units, such as m 2 , cm 2 , and km 2 .

( Using Area to Find Volume
Area can be used to find the volume of an object according to the following equation:
Volume = Area x height
1.
What is the volume of a box 5 cm tall whose lid has an area of 9 cm 2 ?
45 cm 3

( Using Area to Find Volume
2. A crate has a volume of 48 m 3 . The area of its bottom side is 16 m 2 . What is the height of the crate?
3. A cube with a volume of 8,000 cm 3 has a height of 20 cm. What is the area of one of its sides?
2. 3m
3 . 400 cm 2

• The original standards for the kilogram and meter are kept in the International
Bureau of Weights and Measures in
Sevres, France.
They are made of 90 percent platinum and 10 percent iridium.

• Another derived quantity is density.
Density is mass per unit volume. So an object’s density is the amount of matter it has in a given space. To find density (D), first measure mass ( m ) and volume ( V ).
Then use the following equation: m
D
 v

• For example, suppose you want to know the density of a gear. Its mass is 75 g and its volume is 20 cm 3 .
You can calculate the gear’s density like this:
D
 m
 v
75 g
20 cm
3
 g
3 .
75 cm
3

• Science is exciting and fun, but it can also be dangerous.
So don’t take chances!
Always follow instructions, and don’t take shortcuts —even when you think there is little or no danger.

cont
• Before starting an experiment, get your teacher’s permission and read the lab procedures carefully.
Pay particular attention to safety information and caution statements. The chart on page 27, shows the safety symbols used in this book. Get to know these symbols and what they mean by reading the safety information on page 622.
This is important!
If you are still unsure about what a safety symbol means, ask!

1. What does SI stand for ?
2. What is the SI unit of length?
Volume? Mass? Temperature?
3. Name two safety rules of science?

1. International System of Units
2. Meter, cubic meter, gram, kelvin
3.
Follow directions, and don’t take shortcuts

Measuring Skills; Graduated Cylinder
When using a graduated cylinder to measure volume, use the following procedure:
1. Make sure the cylinder is on a flat, level surface.
2. Move your head so that your eye is level with the surface of the liquid.
3. Read the mark closest to the liquid level. On glass graduated cylinders, read the mark closest to the center of the curve (meniscus) in the liquids surface.

Measuring Skills; Meter stick or Metric
Ruler
When using a meter stick or metric ruler to measure length, keep the following procedures in mind:
1. Place the ruler firmly against the object to be measured.
2. Align one edge of the object exactly with the zero end of the ruler.
3. Look at the outer edge of the object to see which of the marks on the ruler is closest to that edge. Note: Each small slash between the centimeters represents a millimeter, which is one-tenth of a centimeter.

Example: Write the number 653,000,000 in scientific notation.
Step 1: Write the number without the place-holding zeros. 653
Step 2: Place the decimal point after the first digit.
6.53
Step 3: Find the exponent by counting the number of places that you moved the decimal point.
6.53000000 .
The decimal point was moved eight places to the left. Therefore, the exponent of 10 is a positive 8. Remember, if the decimal point had to be moved to the right, the exponent would be negative.
Step 4: Write the number 750,000,000,000 in scientific notation.