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1 Grade 8

2 Cover Image: light echo NASA/ESA/Hubble Heritage Team (STScI/AURA) Copyright by Houghton Mifflin Harcourt Publishing Company All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or recording, or by any information storage and retrieval system, without the prior written permission of the copyright owner unless such copying is expressly permitted by federal copyright law. Requests for permission to make copies of any part of the work should be addressed to Houghton Mifflin Harcourt Publishing Company, Attn: Contracts, Copyrights, and Licensing, 9400 Southpark Center Loop, Orlando, Florida Printed in the U.S.A. ISBN XXXX A B C D E F G If you have received these materials as examination copies free of charge, Houghton Mifflin Harcourt Publishing Company retains title to the materials and they may not be resold. Resale of examination copies is strictly prohibited. Possession of this publication in print format does not entitle users to convert this publication, or any portion of it, into electronic format.

3 Contents Using Your Student Edition Companion Notebook vi Unit 1 The Nature of Science Lesson 1 What Is Science? 1 STEM Engineering and Technology 4 Lesson 2 Scientific Knowledge 6 Lesson 3 Scientific Investigations 9 Think Science 12 Lesson 4 Science and Society 13 Unit Review 17 Unit 2 Measurement and Data Lesson 1 Representing Data 21 Do the Math 24 Lesson 2 Scientific Tools and Measurement 25 Unit Review 29 Unit 3 Introduction to Chemistry Lesson 1 The Atom 33 Lesson 2 The Periodic Table 36 Lesson 3 Electrons and Chemical Bonding 39 Lesson 4 Chemical Reactions 41 Think Science 44 Unit Review 47 Unit 4 Forces and Motion Lesson 1 Matter in Motion 51 Lesson 2 Balanced and Unbalanced Forces 54 Lesson 3 Newton s Laws of Motion 57 Unit Review 61 Contents iii

4 Unit 5 The Earth-Moon-Sun System Lesson 1 Earth s Days, Years, and Seasons 65 Lesson 2 Moon Phases and Eclipses 67 STEM Engineering and Technology 69 Lesson 3 Earth s Tides 71 Unit Review 75 Unit 6 The Universe Lesson 1 Structure of the Universe 79 Do the Math 82 Lesson 2 Stars 83 Lesson 3 The Life Cycle of Stars 85 Lesson 4 Observing the Universe 88 Lesson 5 The Origin of the Universe 91 Unit Review 95 Unit 7 Processes that Shape Earth Lesson 1 The Theory of Plate Tectonics 99 Lesson 2 Plate Tectonics and Landforms 102 Lesson 3 Weathering, Erosion, and Deposition 105 Think Science 108 Lesson 4 Topographic Maps 109 Lesson 5 Images of Earth s Surface 112 Unit Review 117 Unit 8 Earth s Oceans and Atmosphere Lesson 1 Wind in the Atmosphere 121 Lesson 2 Ocean Currents 124 Lesson 3 Global Weather Patterns 127 iv STEM Engineering and Technology 130 Lesson 4 Weather Maps and Weather Prediction 132 Unit Review 137 Contents

5 Unit 9 Ecosystems Lesson 1 Ecosystem Ecology 141 STEM Engineering and Technology 144 Lesson 2 Ecology of Terrestrial Ecosystems 146 Do the Math 148 Lesson 3 Ecology of Freshwater and Estuary Ecosystems 149 Lesson 4 Ecology of Marine Ecosystems 152 Lesson 5 Environmental Changes and Populations 155 Unit Review 159 Contents v

6 Using Your Student Edition Companion Notebook Use this Companion Notebook to write answers to questions that appear in the print or digital Student Edition. First, find your assigned lesson in the print or digital Student Edition. Then, use the Table of Contents at the front of this notebook (pages iii v) to find the pages that correspond to the Student Edition lesson. Work with the Student Edition and Companion Notebook side by side. Lesson Scientific Investigations ESSENTIAL QUESTION How are scientific investigations conducted? 3 By the end of this lesson, you should be able to summarize the processes and characteristics of different kinds of scientific investigations. 8.2A plan and implement comparative and descriptive investigations by making observations, asking well-defined questions, and using appropriate equipment and technology 8.2B design and implement comparative and experimental investigations by making observations, asking well-defined questions, formulating testable hypotheses, and using appropriate equipment and technology 8.2D construct tables and graphs, using repeated trials and means, to organize data and identify patterns Superconducting magnet assemblies, such as the one shown here, help to guide charged particles moving at almost the speed of light. Scientists study the colliding particles to investigate the nature of matter and energy. Image Credits: Martial Trezzini/epa/Corbis Engage Your Brain 1 Evaluate Check T or F to show whether you think each statement is true or false. T F Every scientific investigation is an experiment. You could do an experiment to see if eating breakfast helps students raise their grades. Scientists need fancy instruments to do experiments. Scientists must repeat an experiment for it to be useful. Active Reading 3 Synthesize The word experiment comes from the Latin word experiri, meaning to try. What do you think the meaning of the word experiment is? Quick Labs The Importance of Replication Improving an Electromagnet Exploration Lab Road Safety 2 Infer What do you think the scientists who gathered the data for this graph were studying? Average Temperature in Minneapolis Temperature ( C) J F M A M J J A S O N D Month Vocabulary Terms experiment dependent variable observation data hypothesis control variable independent variable 4 Identify This list contains the vocabulary terms you ll learn in this lesson. As you read, circle the definition of each term. Lesson 3 Scientific Investigations Unit 1 The Nature of Science Answers fo current tho 1. F; T; F; 28/01/13 11:08 AM 2. They w apolis 3. Samp cedur sible 4. Stude Temperature ( C) Average Temperature in Minneapolis Name: Date: Class: Unit 1 Lesson 3 1 Evaluate Check T or F to show whether you think each statement is true or false. T F 8.2A; 8.2B; 8.2D Scientific Investigations (p. 32) Every scientific investigation is an experiment. You could do an experiment to see if eating breakfast helps students raise their grades. Scientists need fancy instruments to do experiments. Scientists must repeat an experiment for it to be useful. 2 Infer What do you think the scientists who gathered the data for this graph were studying? 5 Explain Why should hypotheses be testable? 6 Infer Write a hypothesis offering a possible explanation of what will happen to the plant shown in the photo in the Student Edition. 7 Apply Suppose you want to test the hypothesis that plants grow taller when they receive more sunlight. Identify an independent variable and a dependent variable for this investigation. -20 J F M A M J J A S O N D Month 3 Synthesize The word experiment comes from the Latin word experiri, meaning to try. What do you think the meaning of the word experiment is? 10 Apply Give another example of a scientific investigation that would require both observation and experiments. Lesson 3 Scientific Investigations 9 What is included in this Companion Notebook? Most numbered questions and activities from the Student Edition are included in this notebook. All Lesson Review pages and Unit Review pages are reproduced exactly from the Student Edition. Plus, all You Try It! pages from Think Science, STEM Engineering and Technology, and Do the Math unit activities are included exactly as they appear in the Student Edition so that you can practice new skills. vi Using Your Student Edition Companion Notebook What is not included in this Companion Notebook? Some questions in the Student Edition are not included in this notebook. Questions that would require you to underline words or draw on images in the Student Edition are not repeated in the Companion Notebook. Also not included are activities that require research outside the book, such as Think Outside the Book questions and questions from Why It Matters sections.

7 Unit 3 Lesson 1 The Atom (p. 112) 8.5A; 8.5B 1 Identify Read over the following vocabulary terms. In the spaces provided, place a + if you know the term well, a ~ if you have heard the term but are not sure what it means, and a? if you are unfamiliar with the term. Then, write a sentence that includes the word you are most familiar with. Example Sentence: As scientists learned new information about atoms, they had to revise the model of the atom. revise: atom electron 5 Describe Who was Democritus? neutron proton nucleus Sentence using known word: 6 Analyze Look at the picture in the Student Edition. What can you infer about atoms from this image? What can t you infer from the image? 2 Compare Use the figure shown in the Student Edition to answer the questions below. Check T or F to show whether you think each statement is true or false. T F Electrons move in orbits in the same way planets orbit the sun. If this were a model of the atom, the nucleus would be in the same place as the sun. 8 Model Describe how you would show J. J. Thomson s model of the atom using small beads and clay. 3 Apply Use context clues to write your own definition for the words theory and revise. Example Sentence: The scientist developed a theory to explain the structure of the atom. theory: Lesson 1 The Atom 33

8 9 Analyze Today s model of the atom looks different from the models that came before it. Why has the model of the atom changed? 14 Calculate Look at the model of a helium atom shown in the Student Edition. Use this model to find its atomic number and mass number. Atomic number: Mass number: 11 Summarize Complete the following table with information about the parts of the atom. Part of the atom Location in the atom Electric charge Relative mass Proton Slightly less massive than a neutron Nucleus 1 12 Compare How are two atoms of the same element alike? 34 Unit 3 Introduction to Chemistry

9 Lesson Review Vocabulary Draw a line to connect the following terms to their definitions. 1 atom 2 proton 3 neutron A a positively charged atomic particle B an uncharged atomic particle C the smallest particle of an element that has the chemical properties of that element Critical Thinking Lesson Use this diagram to answer the following questions. 1 Key Concepts 4 Compare Compare the charges and masses of protons, neutrons, and electrons. 8 Analyze The red sphere represents a proton. What is the atomic number of this atom? Explain how you found the atomic number. 5 Explain How can atoms make up all of the substances around you? 9 Apply What is the mass number of an isotope of this atom that has 2 neutrons? 10 Analyze Where are the nucleus and the electrons located in this atom? 6 Compare How does the current model of the atom differ from J. J. Thomson s model? 7 Calculate What is the atomic number of a sodium atom that has 11 protons and 12 neutrons? 11 Infer If atoms are made of smaller parts such as electrons, why are atoms considered the basic unit of matter? Lesson 1 The Atom Lesson 1 The Atom

10 Unit 3 Lesson 2 The Periodic Table (p. 124) 8.5B; 8.5C 1 Describe Write a word or phrase beginning with each letter of the word GOLD that describes the properties of the gold coins shown in the Student Edition. G O L D 2 Describe As you will learn in this lesson, elements are arranged by their properties on the periodic table. What other objects are often arranged by their properties? 5 Identify Observe the appearance of the six elements shown in the Student Edition. Create two or three categories that group the elements by similar properties. On the lines below, write the name of the category in which the element belongs. Sulfur: Chlorine: Copper: Bromine: Mercury: Bismuth: 6 Explain How did Henry Moseley revise Mendeleev s periodic table? 3 Preview Before you begin reading this lesson, look through the pages and read the headings and subheadings. The headings show how information is organized in the lesson. After you read the headings and subheadings, write a short description of what the lesson will cover. 7 Apply What are you doing this week? Fill in the calendar on the next page with activities or plans you have for this week and next. Do any events occur periodically? Explain. 36 Unit 3 Introduction to Chemistry

11 Sunday Monday Tuesday 8 Analyze According to the periodic table, how many elements are a liquid at room temperature? 9 Analyze According to the periodic table, how many elements are metalloids? 10 Apply What is the average atomic mass of aluminum? Wednesday Thursday 11 Identify Look at the photos in the Student Edition. Fill in the blanks with the word metal, nonmetal, or metalloid. Iron: Silicon: Carbon: 12 Explain Why do elements within a group have similar chemical properties? Friday Saturday 14 Analyze List three other elements that have 1 valence electron. (Hint: Refer to the periodic table.) 15 Analyze List three other elements that have 8 valence electrons. (Hint: Refer to the periodic table.) Lesson 2 The Periodic Table 37

12 8_CFLAESE365756_182A final LKell Name: Les Date: Class: 1. Lesson Lesson Review Vocabulary Critical Thinking Draw a line to connect the following terms to their definitions. Use this graphic to answer the following questions. 1 metal 2 nonmetal 3 metalloid A an element that has properties of both metals and nonmetals 28 C an element that conducts heat and electricity poorly 4 Identify Elements in the same on the periodic table have the same number of valence electrons. 5 Identify Properties of elements within a on the periodic table change in a predictable way from one side of the table to the other. 6 Identify The number of in an atom determines the identity of the element Cu Copper Palladium Key Concepts Nickel Pd Ni B an element that is shiny and that conducts heat and electricity well Ag Silver Infer What can you infer about copper and silver based on their position relative to each other? Apply How does the nucleus of a copper atom compare to the nucleus of a nickel atom? 7 Describe What is the purpose of the zigzag line on the periodic table? 38 Unit 3 Introduction to Chemistry Lesson 2 The Periodic Table Apply Thorium (Th) has an average atomic mass of u and an atomic number of 90. In the space below, draw a square from the periodic table to represent thorium. 11 Explain Explain how chemists can state with certainty that no one will discover an element that would appear on the periodic table between sulfur (S) and chlorine (Cl).

13 Unit 3 Lesson 3 8.5B; 8.5C Electrons and Chemical Bonding (p. 136) 1 Predict Check T or F to show whether you think each statement is true or false. T F The nucleus of an atom does not change when the atom undergoes a chemical reaction. An atom does not react with other atoms if it has the same number of protons as it has electrons. All of an atom s electrons can interact with the electrons of other atoms to form bonds. 2 Describe Fill in the blank with the word or phrase that you think correctly completes the following sentences. Use the model of a lithium atom shown in the Student Edition. Write your answers on the lines below the sentences. The represents the location of the electrons. Example sentence: A chemical bond can form between two atoms. bond: 5 Describe What are chemical bonds? 8 Apply Look at the diagram of a chemical reaction shown in the Student Edition. How many of each type of atom are there on each side of the arrow? H: Cl: 9 Infer How can you tell that atoms are not created or destroyed by the chemical change shown in the Student Edition? The is represented by the red and silver spheres. 3 Apply Many scientific words, such as bond, also have everyday meanings. Use context clues to write your own definition for each meaning of the word bond. Example sentence: Zach used glue to form a bond between the broken parts of the chair. bond: 10 Describe Look at the models of hydrogen in the Student Edition. Write a caption for each model of hydrogen describing what it shows. Hydrogen model (top): Hydrogen model (bottom): 14 Apply How many valence electrons do nitrogen (N) and phosphorus (P) have? N: P: Lesson 3 Electrons and Chemical Bonding 39

14 Lesson Review Vocabulary Circle the term that best completes each of the following sentences. 1 A chemical bond joins atoms / electrons together in a molecule. 2 In the Bohr model of an atom, valence electrons are shown in the innermost / outermost energy level. Key Concepts 3 Relate Which of the following can happen during a chemical change? A Atoms gain or lose protons and change into new types of atoms. B Bonds break, and new bonds form. C Nuclei of atoms break apart and the subatomic particles recombine. D All of the electrons in the atom are lost. 4 Explain Atoms can gain, lose, or share electrons during a chemical change. Why doesn t this cause the atoms identities to change? Critical Thinking N Lesson Use this model of a nitrogen atom to answer the following questions. 7 Analyze How many valence electrons do nitrogen atoms have? 8 Infer Explain whether nitrogen atoms will form bonds with other atoms. 3 9 Distinguish How would a Bohr model of a neon atom differ from this model of nitrogen? 5 Identify Sulfur (S) is in Group 16 of the periodic table. How many valence electrons does an atom of sulfur have? 6 Model Find beryllium (Be) on the periodic table. In the space below, draw a Bohr model of a beryllium atom. 40 Unit 3 Introduction to Chemistry 10 Apply Imagine that you need to make a model that shows the locations of the parts of a sodium atom. Explain which type of model you would use. Lesson 3 Electrons and Chemical Bonding 145

15 Unit 3 Lesson 4 Chemical Reactions (p. 148) 8.5D; 8.5E; 8.5F 1 Identify Unscramble the letters below to find two types of energy that can be released when chemical reactions occur. Write your words on the blank lines. GLITH DSNUO 2 Describe Write your own caption to the photo shown in the Student Edition. Describe what kind of changes have happened to the ship and anchor. 5 Identify Look at the photos in the Student Edition. For each photo, identify the evidence that a chemical reaction has taken place. Write your answers on the lines below. A B C D 3 Synthesize You can often define an unknown word if you know the meaning of its word parts. Use the word parts and sentence below to make an educated guess about the meaning of the word exothermic. exo- therm- Word part Meaning go out, exit heat Example sentence: Exothermic reactions can sometimes quickly release so much heat that they can melt iron. exothermic: 6 Identify Circle the subscript in the chemical formula below. H 2 O 7 Analyze Look at the chemical reaction shown in the Student Edition. Use what you know about chemical formulas to identify the product in this reaction. 8 Apply Look at the chemical reaction shown in the Student Edition. How many atoms of each element are in one molecule of the product? 9 Compare What is the difference between a coefficient and a subscript? Lesson 4 Chemical Reactions 41

16 10 Calculate Fill in the blanks below to balance the chemical equation. Sketch the products and reactants to show that the number of each type of atom is the same. 12 List Name three everyday exothermic chemical reactions. Identify A Count the atoms of each element in the reactants and product in the unbalanced equation. Look at the Student Edition to see a diagram that shows models of the molecules involved in this reaction. H 2 + O 2 H 2 O 13 Describe What happens to the energy absorbed during an endothermic reaction? H = O = H = O = Solve B To balance the number of each type of atom, place coefficients in front of the appropriate chemical formulas. Sketch the products and reactants, showing the correct number of molecules of each. 14 Compare Use the Venn diagram to compare endothermic and exothermic reactions. Write words and phrases to complete each part of the Venn diagram on the lines below. H 2 + O 2 H 2 O Endothermic Both Exothermic + Endothermic H = O = H = O = Both 42 Unit 3 Introduction to Chemistry Exothermic

17 Lesson Review Vocabulary Draw a line to connect the following terms to their definitions. 1 reactant 2 product Key Concepts A a substance that is produced by a chemical reaction B a substance that participates in a chemical reaction 3 Describe What happens to the atoms in the reactants during a chemical reaction? 4 Explain How does a balanced chemical equation show that mass is never lost or gained in a chemical reaction? Critical Thinking + Lesson Use this diagram to answer the following questions. 4 7 Model The reactants in the above reaction are hydrogen (H 2 ) and nitrogen (N 2 ). The product is ammonia (NH 3 ). In the space below, write a balanced chemical equation that represents the reaction. 8 Analyze This reaction releases energy as heat. Explain whether the reaction is exothermic or endothermic and whether it obeys the law of conservation of energy. 5 Relate Describe four ways you could increase the rate of a chemical reaction. 9 Evaluate Two colorless solutions are mixed together. Bubbles form as the solution is stirred. Give two possible explanations for this result. 6 Compare How do exothermic and endothermic reactions differ? 10 Apply The chemical formula of glucose is C 6 H 12 O 6. What are the names of the elements in glucose, and how many atoms of each element are present in a glucose molecule? Lesson Lesson 4 Chemical 4 Chemical Reactions Reactions

18 You Try It! Acid precipitation can cause a lake to become acidic and unsuitable for living things. One way to reduce the acidity is to add a base. The chemical equation below shows the reaction that takes place when the base calcium hydroxide reacts with sulfuric acid in acid precipitation. Use the skills you ve reviewed to balance this chemical equation. Think Science The acidity of a lake can be adjusted by adding a base. 1 Identify how many atoms of each element are present in each chemical formula. Complete the table at the right by identifying the number of each type of atom in the reactants and in the products. (Hint: You may refer to the periodic table to find the name of unfamiliar elements.) Ca(OH) 2 + H 2 SO 4 CaSO 4 + H 2 O Reactants Products Calcium = 1 Calcium = 1 2 Compare the number of each type of atom in the reactants to the number of each type of atom in the products. Compare the number of atoms in the reactants to the atoms in the products. Which elements are not balanced on both sides of the equation? 3 Add coefficients to balance the chemical equation. Add coefficients in front of the chemical formulas at the right to balance the chemical equation. 4 Check your work. Are there equal numbers of each type of atom on both sides of the yields sign? Record the number of each type of atom in the table. 44 Unit 3 Think Science Ca(OH) 2 + H 2 SO 4 CaSO 4 + H 2 O Reactants Products Image Credits: Eco Images/Universal Images Group/Getty Images

19 My Notes Unit 3 Introduction to Chemistry 45

20 46 Unit 3 Introduction to Chemistry

21 Unit 3 Review Name Vocabulary Fill in the blank with the term that best completes the sentence. Unit 3 Review 8.5C 1 Elements in the periodic table are arranged in columns, or. 2 A(n) is the smallest particle of an element that has the chemical properties of that element. 3 A(n) is a negatively charged subatomic particle. 4 A chemical is an interaction that holds two atoms together. 8.5D 5 A combination of chemical symbols and numbers to represent a substance is a chemical. Key Concepts Choose the letter of the best answer. 8.5B 6 The chart below gives the atomic number and mass number of two elements. Element A Element B Atomic number 10 9 Mass number How many protons does Element B have? A 9 C 19 B 10 D E 7 Which of the following is an example of an endothermic reaction? (Hint: Step 1. Recall what happens to energy in an endothermic reaction. Step 2. Identify the event that matches how energy behaves during an endothermic reaction.) A a cake baking B a candle burning C a firework exploding D a piece of wood smoldering Unit 3 Introduction to Chemistry Unit 3 Review

22 Name: Date: Class: Unit 3 Review continued 8.5A 8 Which model of an atom is correctly labeled? A Proton A Neutron Electrons B B Proton Nucleus Nucleus Proton B Neutron Electrons Neutron Proton Nucleus Electrons B Neutron Nucleus Proton Electrons Proton Nucleus Nucleus C Electrons D Electrons C Neutron Proton Neutron Proton Nucleus Neutron D + + Electrons Nucleus + Proton Nucleus Proton Neutron Proton DNucleus Electrons Neutron Electrons Neutron Electrons Proton Electrons D Nucleus Proton Electrons Neutron 8_CFLAEAG365848_24A First Pass Electrons Precision Graphics 48 Unit 3 Introduction to Chemistry 8_CFLAEAG365848_24A 166 Unit 3 Introduction to Chemistry First Pass Precision Graphics 8_CFLAEAG365848_24A First Pass Precision Graphics Houghton Houghton Mifflin Mifflin Harcourt Harcourt Publishing Publishing Company Company

23 8.5C Name 9 Magnesium has one more valence electron than lithium has. What can you infer about magnesium s location on the periodic table? (Hint: Step 1. Recall how the number of valence electrons affects placement of an element on the periodic table. Step 2. Infer which statement is true based on how the number of valence electrons affects placement on the periodic table.) Unit 3 Review A Magnesium is in the first group. B Magnesium is directly below lithium. C Magnesium and lithium are in different groups. D Magnesium is directly to the right of lithium. 10 Which of the analogies best describes a Bohr model of an atom? (Hint: Step 1. Recall what the Bohr model looks like. Step 2. Decide which analogy best fits what the Bohr model looks like.) A A Bohr model is like a bowling ball because they are both solid spheres. B A Bohr model is like a model of the solar system because they both show orbits around a massive center. C A Bohr model is like a string of beads because they both contain small parts that are lined up in a row. D A Bohr model is like a jigsaw puzzle because they are both made up of small parts that are all joined together. Gridded Response Write your answer in the boxes, then bubble in the corresponding number in the grid below. 8.5D 11 The following chemical equation shows the reaction of methane and oxygen to form carbon dioxide and water. CH 4 + 2O 2 CO 2 + H 2 O What coefficient must be placed in front of water to balance the equation? Unit 3 Introduction to Chemistry 49 Unit 3 Review 167

24 Unit 3 Review continued Critical Thinking Answer the following questions in the space provided. 8.5C 12 List three properties of metals that nonmetals typically do not have. Describe where metals and nonmetals are found on the periodic table. What are elements that have some properties of metals and some properties of nonmetals called? Connect ESSENTIAL QUESTIONS Lessons 1 and 3 Answer the following questions in the space provided. 8.5B 13 In the space below, draw a Bohr model of an atom. How many valence electrons does this atom have? What element does your atom represent? Explain. Bohr models do not correctly show the location of electrons in an atom. Explain why they are still useful for predicting bonding of atoms. 50 Unit 3 Introduction to Chemistry