Contents General Tips for Taking Science Tests ........................................................................ 5 Unit 1 – Scientific Inquiry ............................................................................................... 7 Lesson 1: Scientific Investigation ................................................................. 8 Lesson 2: Science Safety ................................................................................ 25 Unit 2 – Earth and Space Science .............................................................................. 35 Lesson 3: Our Solar System........................................................................... 36 Lesson 4: The Sun and Other Stars............................................................. 50 Lesson 5: Earth’s Motions and Patterns .................................................... 58 Lesson 6: Exploring the Solar System and Beyond .............................. 74 Unit 3 – Life Science ........................................................................................................ 87 Lesson 7: Ecosystems ...................................................................................... 88 Lesson 8: Energy in Ecosystems .................................................................. 98 Lesson 9: Relationships in Ecosystems .................................................. 111 Lesson 10: Changing Ecosystems............................................................ 121 Unit 4 – Physical Science ............................................................................................ 135 Lesson 11: Forces and Motion .................................................................. 136 Lesson 12: Light ............................................................................................. 148 Lesson 13: Sound .......................................................................................... 161

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Glossary ............................................................................................................................ 170

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Lesson

1

Scientific Investigation What is science? Scientists study many different kinds of things. An astronomer studies objects in space. A chemist studies matter and how it changes. An ornithologist studies birds. But all these things have something in common. They are all part of the natural world. Science is the study of the natural world.

Words to Know analyze communicate conclusion data

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data table experiment field study hypothesis

investigation measurement observation variable

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All scientists have something in common, too. They are curious. They ask questions about the natural world and then try to find answers. In this lesson, you will learn about asking and answering scientific questions.

Unit 1 Scientific Inquiry

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Making Observations and Asking Scientific Questions Where do scientists start to look for answers to their questions? They often start with an observation. An observation is information gathered with the senses. An observation is something you see, hear, touch, smell, or taste. Sometimes, an observation will cause you to ask a question. For example, you might observe that there are puddles on the sidewalk after it rains. Then you see that the puddles disappear after the sun shines for a while. This observation might lead you to ask, “Where did the water go?” Not all questions are scientific questions. A scientific question must be a testable question. You must be able to test a possible answer to the question. For example, you might ask, “Will a pan of water come to a boil faster if I add salt to it?” You can test a possible answer to the question. You can make further observations to find the answer. But “Does water with salt added to it taste good?” is not a testable question. You cannot answer it by testing. Whether or not water with salt added to it tastes good is an opinion. You cannot prove an opinion. Consider this question: “Do plants that get more hours of sunlight each day grow taller than plants that get fewer hours of sunlight each day?” Is it a testable question? Why or why not?

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Now write one scientific question of your own on the lines below.

What types of observations would help you answer the scientific question that you wrote?

Lesson 1 Scientific Investigation

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Making and Testing Hypotheses After making an observation and asking a scientific question, a scientist states a hypothesis. A hypothesis is a possible answer to a scientific question. A hypothesis should be based on what a scientist already knows. Suppose you say that the water in rain puddles dries up faster when the air temperature is higher. You have just stated a hypothesis. Your statement is based on something you already know—that water evaporates, or changes to a gas. The next step is for you to test your hypothesis. You have to find out whether temperature affects how fast water evaporates. A hypothesis must be testable to be valid, or acceptable. But a hypothesis does not have to be correct. In fact, great scientific work can result from incorrect hypotheses. For example, scientists long ago thought that heat was a type of invisible liquid. This idea was wrong. But by testing it, scientists learned about the true nature of heat. A hypothesis is invalid only if it is not testable. Are the following hypotheses valid or invalid? Explain why. Robins’ eggs are blue.

The average goblin is 60 centimeters tall.

To test a hypothesis, a scientist does an investigation. An investigation is a close study of something done to answer a question about it. An investigation involves gathering information to see if a hypothesis may be true.

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Earth is flat.

Unit 1 Scientific Inquiry

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When you think of science, you may think of people doing experiments. An experiment is one kind of investigation. An experiment is a carefully controlled test. In an experiment, you test the effect of one thing on another. You can think of an experiment as performing an action to see what happens because of your action. For example, suppose your hypothesis is that plant shoots will always grow upward, toward the sky, no matter which way the plant’s roots are tilted. You might test this hypothesis by tilting some plant pots in different directions. As the plants grew, you would observe the direction of their growth. You would see what happens because of your action of tilting the plant pots. An experiment is just one type of scientific investigation. Another type of investigation is a field study. A field study is a scientific investigation carried out in a natural setting. This type of investigation is most often done outdoors. In a field study, a scientist observes, measures, and compares, just as in other investigations. But in a field study, a scientist does not make changes to the natural world. For example, a scientist might observe that woodchucks hibernate longer after rainier summers. To explain this observation, he states a hypothesis. Because wetter summers help plants grow, there is more food during fall. When woodchucks eat more food, they hibernate longer. The scientist cannot change the amount of rain that falls. And he cannot control the amount of food that woodchucks eat. But the scientist can do a field study. He can observe, measure, and gather information. He can see if there is a true connection between rainier summers and longer hibernation.

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Describe one difference between an experiment and a field study.

George thinks that fifth-grade boys have bigger feet than fifth-grade girls. He wants to test this hypothesis. Will George do an experiment or a field study? Explain why he would choose one over the other.

Lesson 1 Scientific Investigation

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Designing an Investigation Suppose you state the hypothesis that temperature affects how fast the water in a puddle will evaporate. How could you test this hypothesis scientifically? You would have to design an investigation, such as an experiment. An experiment tests whether one factor will affect another. In an experiment, you can change the factor that you think produces an effect. For example, you can place water in shallow pans, so that it is similar to the water in puddles. You can place each pan in an area with a different temperature. Then you can measure how long it takes the water in each pan to evaporate. The temperature of the air is a variable. The time it takes the water to evaporate is another variable. A variable is anything that can change in an investigation. Scientists change some variables on purpose but do not change other variables. The other variables are only measured and recorded. An experiment should change only one variable at a time. By changing only one variable, you can be pretty sure that it is the cause of any effects you observe in another variable. Another way to be sure of a result is to repeat an investigation. If you do the same experiment two or three times and get similar results each time, you can trust your results. You know that nothing wrong or unusual happened to cause the results.

Outdoors, in sunlight

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Indoors, in shade

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Julia decides to test the hypothesis that a higher temperature will speed up the evaporation of water. She fills two shallow pans with water. She places each pan in a place with a different temperature, as in the diagram below. She measures the air temperature in each place. Then she observes the water level in each pan over time. She records the time it takes for the water in each one to evaporate completely.

Unit 1 Scientific Inquiry

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Think about Julia’s investigation. What variable is Julia changing?

What variable will Julia measure to look for effects of the first variable?

People in Science Who was the first scientist? No one can answer that question. But the first scientist to carry out experiments to test a hypothesis may have been a man named al-Hassan Ibn al-Haytham. He lived and worked in Egypt in the early 1000s, when Europe was still in the Middle Ages. He used methods similar to those that scientists use today. Ibn al-Haytham was very interested in how we see. At that time, people still believed the Greek thinker Aristotle’s ideas about sight. Aristotle thought that people sensed colors and shapes because rays came out of their eyes. But Ibn al-Haytham had a different explanation. He thought that objects reflect light. He suggested that reflected light enters the eye and allows people to see objects. Ibn al-Haytham tested his hypothesis with experiments in which he used candles and mirrors. He discovered that light is reflected and changed in predictable ways. These experiments were the beginning of a new field of science, called optics. Optics is the study of how light behaves. European scientists, such as Isaac Newton, later studied Ibn al-Haytham’s books. Scientists used the knowledge from his books to make more discoveries. Duplicating any part of this book is prohibited by law.

Ibn al-Haytham

Gathering Data Scientists answer questions by making observations. They also take measurements. Scientists record those observations and measurements in a notebook. Data are the pieces of information gathered during an investigation. Scientists use tools to gather data. Scientific tools help you observe the natural world. They give you information your senses alone cannot give you. For example, your doctor uses a stethoscope to listen to the sounds your heart makes. Your doctor could not clearly hear your heart beating with his or her ears alone. Lesson 1 Scientific Investigation

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Some scientific tools, such as hand lenses and microscopes, allow you to see small details and tiny objects. And some tools, such as telescopes, allow you to see objects that are far away. You could not see these objects with your unaided eyes. Some scientific tools help you take measurements. A measurement is a description of how much of something there is. It includes both a number and a unit. Feet and inches are common units. For example, if you measure how tall a person is, your measurement might be 4 feet, 5 inches. You might use a tape measure or a yardstick to measure how tall a person is. Scientific measurements use metric units such as centimeters, meters, and kilometers to measure height, length, and distance. You can also measure your height with a meterstick. Volume is the amount of space something takes up. Milliliters and liters are units of volume. You can use a graduated cylinder to find volume. Look at the example in the pictures below. Volume of water

Volume of water and object

mL 100

mL 100

90

90

80

80

70 60 50

92 mL

70

50 mL

60 50

40

40

30

30

20

20

10

10

What is the volume of the rock?

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First, add water to the graduated cylinder. Measure the volume of the water. Then place the object in the cylinder. Measure the total volume of the object and the water. In the example above, the volume of water in the cylinder on the left is 50 milliliters. The abbreviation for milliliters is mL. The cylinder on the right shows that a rock has been added. The total volume of the rock and the water is 92 mL. You can find the rock’s volume by subtracting the volume of the water from the total volume.

Unit 1 Scientific Inquiry

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You can use other tools to measure amounts such as weight, time, and temperature. A spring scale is used to measure weight. You probably measure your weight in pounds and ounces, but scientists measure weight in units called newtons. To measure time, you can use a stopwatch or a clock. To measure temperature, you use a thermometer. Scientists often measure temperature in degrees Celsius. Some scientific tools are shown below.

Science Tools ˚C 80 70 60 50 40 30 20 10 0 -10 -20 -30

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Graduated cylinder

Telescope

2

3

4

5

6

7

8

9

10

Ruler or meterstick

Thermometer

NW

S

N

W SW

N

Hand lens

Microscope

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NE E

S

SE

Compass

Magnet

Spring scale

Stopwatch

Look at the table of scientific measurements below. Complete the table by filling in the scientific unit or tool that is missing from each row. Scientific Measurements Property

Unit

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Distance Weight

Ruler or meterstick newton

Temperature Time Volume

Tool

Thermometer second, minute, hour Graduated cylinder

An object’s speed is the distance it moves divided by the amount of time it is moving. Which two tools could be used to measure speed?

Lesson 1 Scientific Investigation

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You may measure your weight by standing on a bathroom scale. If you record this measurement every day for a month, you are gathering data. But not all data are reliable, or able to be trusted. To be reliable, data should be as complete as possible. Measurements should be made carefully and under the same conditions each time. Suppose you decide to gather data about your normal daily weight. You decide to measure and record your weight for a month. For the first week, you measure and record your weight every day at the same time. Each time, you take off your shoes first. The next week, you measure and record your weight at a different time on each of three days. On one of those days, you are wearing heavy boots and holding a backpack full of books. You measure and record your weight only once during the third week, right after playing in a basketball game. During the fourth week, you measure and record your weight every other evening before bed. You are wearing the same pajamas, robe, and slippers each time. Would all of your weight data be reliable? For which week would your weight data be the MOST reliable? Explain your answers.

Analyzing Data

After analyzing data, a scientist draws a conclusion. A conclusion is a statement about what observations and data seem to mean. It states whether the data support the hypothesis or do not support it.

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Once you have gathered and recorded data, you must figure out what the data tell you. Do the data support your hypothesis? Or do they tell you that your hypothesis is probably not correct? You need to analyze your data. To analyze something means to study it carefully to understand what it means. Often, it is easier to analyze data that are in the form of a chart or table.

Unit 1 Scientific Inquiry

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Jacob knows that the pollution on the playground is in the form of litter. He thinks that most of the pollution on the playground comes from disposable water bottles. Then he and his friends gather data to see whether his hypothesis is supported. Jacob creates the data table below. A data table is a chart made up of rows and columns. It is used to organize data. Pollution on the Playground Type of Pollution

Number of Items

Glass

30

Plastic

40

Paper

100

Metal

10

Other

5

Do the data support Jacob’s hypothesis? Explain.

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Communicating Data, Discoveries, and Conclusions What if the data from an experiment do not support your hypothesis? You can still learn from your work. You can repeat the experiment to see if you get the same data again. You can change your hypothesis and design a new experiment to test it. You can also communicate, or share information. You and your classmates can share the results of your investigations. Then you will learn from each other. Scientists learn from other scientists. They study each other’s experiments, data, and conclusions. They share their ideas at meetings and in magazines called scientific journals. Scientists must be able to communicate well. They must be able to speak and write clearly. They must be able to present data in ways that are easy to understand, such as in tables, diagrams, and graphs. They must be able to explain their conclusions. Then scientific knowledge can grow.

Lesson 1 Scientific Investigation

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Think about the skills you practice in school. Which ones would you use if you were writing about an experiment for a scientific journal?

Keys to Keep A hypothesis is a possible answer to a scientific question. It is based on scientific facts. A hypothesis can be tested with a scientific investigation. Field studies and experiments are two types of investigations. A variable is anything that can change in an investigation. A reliable experiment changes only one variable at a time. Scientific tools help us observe the natural world. They also help us make measurements. A measurement describes how much of something there is. It uses a number and a unit. Data are measurements and observations. This information is recorded in an organized way.

To analyze data means to study them to figure out what they mean. A conclusion states whether the data support the hypothesis.

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Data can be displayed in tables and graphs. These make the information easier to analyze.

Unit 1 Scientific Inquiry

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Explore It Yourself Does as much water evaporate in a closed container as in an open container? Do this simple experiment to find out.

Materials Needed • water

• clear plastic wrap

• two graduated cylinders or beakers

• rubber band or tape

Step 1: Place equal amounts of water in two graduated cylinders or beakers. Step 2: Measure and record the amount of water in each container. Step 3: Cover the top of one container with clear plastic wrap. Hold the plastic wrap in place with a rubber band or tape. Step 4: For five days, observe and measure the water level in each cylinder or beaker. Record your data in the table below. Step 5: After you have collected the data, analyze it. Write your conclusion on the lines at the bottom of the page. Water Level Data

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Day

Volume of Water in Uncovered Container (mL)

Volume of Water in Covered Container (mL)

Conclusion

Lesson 1 Scientific Investigation

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What Does It Mean? 1. What variable did you change on purpose in your experiment?

2. What factors did you keep the same in your experiment? Identify at least two factors.

3. What variable did you measure?

4. State a hypothesis that your experiment was testing.

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5. What kind of data would support your hypothesis? What kind of data would not support your hypothesis?

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Unit 1 Scientific Inquiry

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Lesson 1 Review 1. A student recorded information about the different types of birds she observed in her school yard during recess. Then she made a chart of her data, as shown below. Birds Seen in the School Yard during Recess Type of Bird Crow Blue jay Chickadee

Number Seen 12 8 20

Bluebird

2

Cardinal

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According to her data, which type of bird did she see most often? A. B. C. D.

chickadee bluebird cardinal crow

2. Which of the following is a measurement? 1249 12 centimeters kilometer square foot

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A. B. C. D.

Lesson 1 Scientific Investigation

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Lesson 1 Review

3. The illustration below shows Ricardo’s experiment. The plants are shown as they looked after 1 week.

Per day 10 mL water 3 h sunlight

Per day 15 mL water 6 h sunlight

Per day 20 mL water 4 h sunlight

Can Ricardo conclude that more hours of sunlight caused the plants to grow bigger? A. B. C. D.

Yes, because the plant that received the least sunlight also received the least water Yes, because the plant the received the least sunlight did not grow the most No, because the plant that received the most sunlight grew the least No, because the plant that received the most sunlight also received the most water

4. Which list gives a correct order of steps for answering a question about the natural world? analyze results, gather data, state a hypothesis, plan an investigation gather data, plan an investigation, state a hypothesis, analyze results state a hypothesis, plan an investigation, gather data, analyze results plan an investigation, state a hypothesis, analyze results, gather data

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A. B. C. D.

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Unit 1 Scientific Inquiry

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Lesson 1 Review

5. Which tool can be used to measure weight? C.

A.

B.

D.

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6. Which tool would be useful during a field study of insects? A.

B.

C.

D.

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80 70 60 50 40 30 20 10 0 -10 -20 -30

Lesson 1 Scientific Investigation

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Lesson 1 Review

7. Which of the following changes would improve an investigation? A. B. C. D.

changing more than one variable doing the investigation more than once measuring in feet and inches instead of centimeters describing observations in words instead of numbers

8. Which of the following would be the final step in a scientific investigation? A. B. C. D.

analyzing data drawing a conclusion communicating results stating a hypothesis

9. Which of these would you measure with a stopwatch? the time it takes a plant to grow 20 centimeters the temperature at which water freezes the time it takes a ball to roll 4 meters the distance a paper airplane travels

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A. B. C. D.

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Unit 1 Scientific Inquiry

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