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59CT

This book is printed on paper containing a minimum of 10% post-consumer waste.

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Table of Contents Connecticut Content Standards/Expected Performances

Letter to the Student . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Test-Taking Checklist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Connecticut Core Science Curriculum Framework Correlation Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Chapter 1

Scientific Inquiry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Lesson 1 Asking Scientific Questions . . . . . . . . . . . . 12 Lesson 2 Designing and Conducting an Experiment 16 Lesson 3 Using Tools to Gather Data . . . . . . . . . . . . 20 Lesson 4 Organizing Data . . . . . . . . . . . . . . . . . . . . . 25 Lesson 5 Using Math to Interpret Data . . . . . . . . . . . 31 Lesson 6 Drawing Conclusions . . . . . . . . . . . . . . . . . 35 Lesson 7 Communicating Scientific Information . . . . 39 Lesson 8 Evaluating Scientific Information. . . . . . . . . 43

C INQ.1, C INQ.3 C INQ.3, C INQ.4 C INQ.5 C INQ.7 C INQ.6 C INQ.8, C INQ.9 C INQ.10 C INQ.2

Chapter 1 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Chapter 2

Physical Science. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Lesson 9 Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Lesson 10 The Periodic Table . . . . . . . . . . . . . . . . . . . 58 Lesson 11 Compounds and Mixtures . . . . . . . . . . . . . 63 Lesson 12 Describing Motion. . . . . . . . . . . . . . . . . . . . 68 Lesson 13 Forces and Motion . . . . . . . . . . . . . . . . . . . 73 Lesson 14 Friction, Gravity, and Circular Motion. . . . . 76 Lesson 15 Work and Simple Machines . . . . . . . . . . . . 81 Lesson 16 Potential and Kinetic Energy. . . . . . . . . . . . 86 Lesson 17 Energy Transformations . . . . . . . . . . . . . . . 90

6.1-C1 6.1-C1 6.1-C2, 6.1-C3 8.1-C22 8.1-C23 8.1-C23, 8.1-C24 7.1-C12, 7.1-C13 7.1-C14 7.1-C14

Chapter 2 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Chapter 3

Life Science. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Lesson 18 Energy for Ecosystems . . . . . . . . . . . . . . . 102 Lesson 19 The Flow of Energy in Ecosystems. . . . . . 106 Lesson 20 Changes in Ecosystems . . . . . . . . . . . . . . 110 Lesson 21 Levels of Organization . . . . . . . . . . . . . . . 115

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6.2-C4 6.2-C6 6.2-C5 7.2-C15

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Lesson 22 Lesson 23 Lesson 24 Lesson 25 Lesson 26 Lesson 27

The Human Respiratory and Circulatory Systems . . . . . . . . . . . . . . . . . 119 The Human Digestive System. . . . . . . . . . 124 The Human Skeletal and Muscular Systems. . . . . . . . . . . . . . . . . . . 127 DNA, Genes, and Chromosomes . . . . . . . 132 Mitosis and Meiosis . . . . . . . . . . . . . . . . . 136 Human Reproduction . . . . . . . . . . . . . . . . 141

7.2-C16 7.2-C16

7.2-C17 8.2-C27 8.2-C25 8.2-C26

Chapter 3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 Chapter 4

Earth and Space Science. . . . . . . . . . . . . . . . . . . . . . . 153 Lesson 28 States of Matter . . . . . . . . . . . . . . . . . . . . 154 Lesson 29 Earth’s Atmosphere . . . . . . . . . . . . . . . . . 158 Lesson 30 Heat Transfer and Weather. . . . . . . . . . . . 162 Lesson 31 Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Lesson 32 Investigating and Predicting Weather. . . 171 Lesson 33 Earth’s Structure . . . . . . . . . . . . . . . . . . . . 175 Lesson 34 Plate Motion and Earth’s Changing Surface . . . . . . . . . . . . . . . . . . . 179 Lesson 35 Weathering and Erosion . . . . . . . . . . . . . . 185 Lesson 36 Gravity and Our Solar System . . . . . . . . . 191 Lesson 37 Earth’s Motions . . . . . . . . . . . . . . . . . . . . . 196 Lesson 38 Phases of the Moon and Tides. . . . . . . . . 201 Lesson 39 Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

6.3-C7 6.3-C7 6.3-C7, 6.3-C8, 6.3-C9 6.3-C9 6.3-C8 7.3-C18, 7.3-C20

7.3-C18, 7.3-C20 7.3-C19 8.3-C28 6.3-C9, 8.3-C29 8.3-C29 8.3-C29

Chapter 4 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 Chapter 5

Science, Technology, and Society . . . . . . . . . . . . . . . 217 Lesson 40 Water Resources. . . . . . . . . . . . . . . . . . . . 218 Lesson 41 How Humans Affect Water . . . . . . . . . . . . 223 Lesson 42 Protecting Water Resources . . . . . . . . . . . 227 Lesson 43 Bacteria and Food Preservation . . . . . . . . 231 Lesson 44 Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

6.4-C10, 6.4-C11 6.4-C11 6.4-C10 7.4-C21 8.4-C30

Chapter 5 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Investigation 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 Investigation 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Pretest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Posttest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 4

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9

Elements 6.1-C1

Getting the Idea Key Words atom element nucleus proton neutron electron neutral atomic number atomic mass chemical symbol reactivity

Everything around you is matter, and so are you yourself. Matter is anything that has mass and volume. Almost all matter you are familiar with is made up of tiny particles called atoms. In this lesson and the next, you will learn about the different kinds of atoms.

Atoms and Elements Atoms are the basic building blocks of most of the matter around you. But atoms are not all alike. There are different kinds of atoms, as you will see. An element is a substance made up of only one kind of atom. Scientists have discovered about 117 elements. Ninety-two elements are found in nature. Carbon, oxygen, gold, silver, and iron are some naturally occurring elements. The remaining elements are synthetic, or made by humans in the laboratory.

Atoms and Their Parts An atom is the smallest particle of an element that has all the properties of that element. Each element is made up of atoms that differ from those of every other element. To understand how atoms differ, you need to look at the particles that make up an atom. The diagram below shows the structure of a carbon atom. Notice that this atom is made up of three different kinds of particles. These are called subatomic particles. Carbon Atom Neutron

Proton (+)

Electron (–)

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Lesson 9: Elements

Did You Know The number of protons in an atom of an element never changes, but the number of neutrons can vary. Most carbon atoms have 6 protons and 6 neutrons, but some have 7 or 8 neutrons. The average atomic mass of carbon is 12.01 amu.

The center of the atom is called the nucleus. The nucleus of most atoms is made up of two kinds of particles: protons and neutrons. Protons carry a positive (  ) charge. Neutrons have no charge. The masses of protons and neutrons are measured in atomic mass units (amu). Each proton and neutron in an atom has a mass of about 1 amu. Electrons are particles that move around in an area outside the nucleus. Electrons carry a negative (  ) charge. Electrons have almost no mass compared to protons and neutrons. The table below summarizes the characteristics of protons, neutrons, and electrons. Characteristics of Subatomic Particles Subatomic Particle

Atomic Mass

Atomic Charge

Proton

1 amu

+1

Nucleus

Neutron

1 amu

0

Nucleus

Electron

—

–1

Location

Outside nucleus

Look at the carbon atom on page 54 again. Notice that the number of protons in the atom is equal to the number of electrons. As a result, each positive charge in the nucleus is balanced by a negative charge in the electrons outside the nucleus. The atom as a whole is electrically neutral—it has no overall charge. The number of protons in the nucleus of an atom is called its atomic number. Each element has a different atomic number. For example, carbon has 6 protons in each atom and an atomic number of 6. Oxygen has 8 protons and an atomic number of 8. Atomic mass is the mass of one atom of an element and is equal to the number of protons and neutrons in the nucleus. The table below shows the atomic masses of several common elements. Atomic Masses of Some Elements Element

Protons

Neutrons

Electrons

Atomic Mass

Carbon (C)

6

6

6

12 amu

Oxygen (O)

8

8

8

16 amu

Sodium (Na)

11

11

11

22 amu

Iron (Fe)

26

29

26

55 amu

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Did You Know Single atoms of oxygen are rare in nature. Most oxygen on Earth is in the form of O2—two atoms of oxygen joined together.

In the table on page 55, notice the letters in parentheses next to the name of each element. These letters are the element’s chemical symbol. A chemical symbol is a code, usually one or two letters, used to represent an element. Each element has its own chemical symbol. C always represents carbon, O always represents oxygen, Fe always represents iron, and so on.

Properties of Elements Each element has different properties, or characteristics. The structure of an element’s atoms determines its properties. For example, pure oxygen and pure hydrogen appear as colorless gases. Carbon is a solid at room temperature. Carbon has several different forms. One form is graphite, a soft, gray substance. Graphite is the main material in pencil “lead.” Another form of carbon is diamond, which is transparent and hard. In fact, diamond is the hardest material found in nature. Iron and aluminum are shiny metals. Iron is silvery gray and heavy. Aluminum is silvery white and lightweight. You will learn more about the properties of metals in Lesson 10. Elements are different in reactivity—the ability to form chemical bonds with other substances. Oxygen is highly reactive. It combines with other substances in the process called burning. Hydrogen is also very reactive. In fact, it causes explosions when it combines with some other elements. Iron reacts easily with water (hydrogen and oxygen) to form rust. Aluminum does not.

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Lesson 9: Elements DISCUSSION QUESTION How are various elements similar and different? LESSON REVIEW

1.

2.

3.

4.

Sodium is an element found in table salt. It contains 11 protons and 12 neutrons. How many electrons are found in a neutral atom of sodium? A.

1

C.

12

B.

11

D.

23

A student left a piece of iron and a piece of aluminum outside in damp air for two weeks. What did the student MOST LIKELY observe at the end of that period? A.

The piece of iron formed rust.

B.

The piece of aluminum formed rust.

C.

Both of the metal pieces formed rust.

D.

Neither of the metal pieces formed rust.

The smallest particle of an element that has all the properties of that element is A.

a proton.

B.

an atom.

C.

a neutron.

D.

a subatomic particle.

Electrons in an atom carry A.

no charge.

B.

a positive charge.

C.

a negative charge.

D.

a negative and positive charge.

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