Chapter 2 Energy, Force, and Motion Lesson 6 Describing Motion C, D; 8.2C, D; 8.4A; 8.6B

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2 Table of Contents Texas Essential Knowledge and Skills Correlation Chart Chapter 1 Matter Lesson 1 Atoms and Elements A*, C; 8.3B, D; 8.5A, B Lesson 2 The Chemical Composition of Earth and Living Things B*, 7.6A Lesson 3 The Periodic Table A; 8.3D; 8.5B, C Lesson 4 Physical and Chemical Changes D*, 8.1A, 8.4B, 8.5E Lesson 5 Chemical Formulas and Reactions D; 8.5D, F Chapter 1 Review Chapter 2 Energy, Force, and Motion Lesson 6 Describing Motion C, D; 8.2C, D; 8.4A; 8.6B Lesson 7 TEKS Force, Motion, and Inertia B; 8.6A, C Lesson 8 Work and Machines E*, 7.7A Lesson 9 Energy and Its Transformations A, 6.9C Lesson 10 Heat A*, B*; 8.2A, C, D, E; 8.4A Lesson 11 Energy Resources and Their Environmental Impact A*, B*; 8.1B Chapter 2 Review Chapter 3 Space Science Lesson 12 Days, Years, and Seasons A*, 8.7A Lesson 13 Lesson 14 Lesson 15 Phases of the Moon and Tides A, D, E; 8.7B, C The Sun and Other Stars A*; 7.9A*; 8.8A, B The Solar System A*, B; 7.9A* Lesson 16 Exploring the Solar System and Beyond C*, 7.9B*, 8.8C Lesson 17 Deep-Sky Objects D, 8.8A Lesson 18 Lesson 19 Galaxies and Distances in Space A; 8.8A, B, D Studying the Universe B D; 8.8C, E Chapter 3 Review *Not directly assessed on the STAAR. 4

3 Chapter 4 Earth Science Lesson 20 Earth s Internal Structure A*; 8.3B, C Lesson 21 The Theory of Plate Tectonics D*, 8.3D, 8.9A Lesson 22 Plate Motion and Earth s Changing Surface C*, D*; 8.9B Lesson 23 Rocks and Minerals B*, C; 6.6B, C*; 6.10B* Lesson 24 Weathering and Erosion A*, B*, C; 8.2E; 8.9C Lesson 25 Using Maps to Study Earth s Surface B*, 8.9C Lesson 26 TEKS Global Winds and Ocean Currents A*; 8.10A, C Lesson 27 Local and Global Weather E, 8.10B Chapter 4 Review Chapter 5 Cells and Organisms Lesson 28 Cells A*, B*; 7.7B*; 7.12D, E*, F Lesson 29 Levels of Organization and Human Body Systems B, C* Lesson 30 Digestion B*, C*; 7.12B Lesson 31 Photosynthesis and Cellular Respiration A*, 7.7B, 7.12D, 8.5F Lesson 32 How Animals Respond to Stimuli A*, B* Lesson 33 How Plants Respond to Stimuli C*; 7.13A*, B*; 8.2B, 8.4A Lesson 34 Heredity and Reproduction D, 7.14A*, B, C Lesson 35 Classification C*, D; 7.11A; 8.2A Lesson 36 Adaptations, Variations, and Survival B*, C; 7.12A*; 8.3D; 8.11C Chapter 5 Review Chapter 6 Organisms and the Environment Lesson 37 Ecosystems E*, F*; 7.10A*; 8.2A; 8.11B Lesson 38 Energy Flow in Ecosystems A*, B*, C*; 8.11A Lesson 39 Changes in Ecosystems A; 7.10C; 8.11B, C Lesson 40 Biodiversity B, 8.11B Lesson 41 Oceans and Other Water Resources C*; 8.11C, D Chapter 6 Review *Not directly assessed on the STAAR. 5

4 Investigations Investigation 1 Testing Conservation of Mass A; 8.2B E; 8.3A; 8.4A, B; Investigation 2 Tracking the Path of a Hurricane A, C E; 8.4A; 8.10C Glossary Comprehensive Review E, F *Not directly assessed on the STAAR. 6 Table of contents

5 Chapter 1 Lesson 1 Atoms and Elements TEKS: 6.5A, C; 8.3B, D; 8.5A, B Key Words atom element nucleus proton charge neutron electron atomic number ion atomic mass chemical symbol compound model electron cloud model Getting the Idea Everything around you is matter. Matter is anything that has mass and volume. Mass is the amount of matter in a substance. Volume is the amount of space the substance occupies. All substances everything you own, everything you touch, even you yourself are made up of different types of matter. Atoms and Elements Atoms are the basic building blocks of most of the matter around you. There are different kinds of atoms. Each kind of atom is an element. An element is one of the basic substances that combine to form all other substances. Elements cannot be broken down into simpler substances by ordinary chemical means. Scientists have discovered about 117 elements. These elements are the building blocks of the matter around you. About 90 of these 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 the atoms of each element 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. Carbon Atom Neutron Proton (+) Electron ( ) 12

6 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. Charge is an electrical property that can be either positive or negative. Neutrons have no charge. The masses of protons and neutrons are measured in atomic mass units (amu). Each proton and neutron has a mass of about 1 amu. Electrons are subatomic particles that exist in an area outside the nucleus. Electrons have a negative ( ) charge. The mass of electrons is insignificant compared to the mass of protons and neutrons. The table below compares protons, neutrons, and electrons. Characteristics of Subatomic Particles Particle Mass Charge Location Proton 1 amu 1 Nucleus Neutron 1 amu 0 Nucleus Electron 1 Outside nucleus Elements and Subatomic Particles The properties, or characteristics, of an element are determined by the structure of its atoms. The main difference between different elements is atomic number. Atomic number is the number of protons in the nucleus of an atom. The number of protons in the nucleus is unique for each element. Therefore, no two elements have the same atomic number. Carbon, for example, has six protons and an atomic number of 6. Look at the carbon atom on page 12 again. Notice that the number of protons in the atom is equal to the number of electrons. Because these numbers are equal, each positive charge in the nucleus is balanced by a negative charge in the electrons around the nucleus. The atom as a whole is electrically neutral and has no overall charge. If the numbers of protons and electrons in an atom are not equal, the atom has a charge. A charged atom is called an ion. Atoms have mass. The atomic mass of an atom is equal to the total mass of protons, neutrons, and electrons in the atom. The unit for atomic mass is the atomic mass unit (amu). Each proton has a mass of about 1 amu. Each neutron also has a mass of 1 amu. Electrons have almost no mass. You can therefore determine the atomic mass by counting the protons and neutrons in an atom. 13

7 The table below gives the atomic masses of several common elements. Atomic Masses of Some Elements Element Protons Neutrons Electrons Atomic Mass Carbon (C) amu Oxygen (O) amu Sodium (Na) amu Potassium (K) amu Iron (Fe) amu Notice the letters in parentheses beside the name of each element in the table above. These letters are the chemical symbol of the element. A chemical symbol is a code, normally composed of one or two letters, used to represent an element. Each element has its own chemical symbol. C always represents carbon, Ca always represents calcium, Fe always represents iron, and so on. Elements Form Compounds A compound is a substance that forms when two or more elements join chemically in a fixed proportion. The atoms that make up a compound bond to one another. Bonds form when the elements making up a compound join by sharing or transferring electrons. The bonds mean the atoms cannot be broken apart easily. A compound has different properties from those of the elements that make it up. For example, table salt is a compound of sodium and chlorine. Sodium (Na) is a soft metal that explodes when combined with water. Chlorine (Cl) is a poisonous gas. When these elements combine to form sodium chloride (NaCl), they form table salt, an edible white solid. Hydrogen and oxygen are both gases at room temperature. They can combine to form water, which is liquid at room temperature. Atomic Theory Scientists use atomic theory to describe the particles that make up matter. Atomic theory states that atoms are the basic building blocks of all matter and atoms are composed of subatomic particles. Atomic theory began in ancient Greece more than 2,500 years ago. Since that time, many different models of the atom have been developed as scientists have learned new information. A model is a representation of an object, system, or process. Scientists use models to study, show, or explain how something functions. Diagrams, threedimensional replicas, and computer simulations are some models used in science. Models are used to describe atoms because atoms are too small to be seen with the unaided eye or even with most microscopes. 14 Chapter 1: Matter

8 Lesson 1: Atoms and Elements A useful model of the atom was developed by a Danish physicist, Niels Bohr. In the Bohr model, electrons move around the nucleus in orbits called energy levels. An energy level is a region in which electrons having similar amounts of energy are likely to be located. The closer electrons are to the nucleus, the lower their energy. The Bohr model is shown below. Bohr Model Nucleus (contains protons [+] and neutrons) Electron ( ) In the Bohr model, electrons can shift position from one energy level to another. Higher energy areas (those farther from the nucleus) can hold more electrons. The maximum numbers of electrons normally held by energy levels 1, 2, 3, and 4 are 2, 8, 18, and 32. The modern model of the atom is the electron cloud model. Electrons exist in an area around the nucleus of an atom called a cloud. Scientists describe electrons as existing everywhere in the electron cloud. An electron can be found anywhere within the electron cloud. Modern Electron Cloud Model Electrons in the cloud absorb and release energy. This changes their location within the atom. When electrons give off energy, they move to lower levels. Energy absorbed or emitted as light, heat, or other forms of energy can be detected. The electron cloud model explains why substances have color, release heat, or give off different types of radiation. This model is not the end, however. The atomic model will continue to change as scientists make discoveries. 15

9 Discussion Question How are compounds and elements similar and different? Lesson Review 1. What are the smallest building blocks of most ordinary matter? A. carbon C. mass B. atoms D. compounds 2. 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. 11 C. 23 B. 12 D A substance that forms when two or more elements join chemically is A. an ion. C. a formula. B. a compound. D. an atom. 4. The nucleus of an atom contains A. only neutrons. B. protons and electrons. C. protons and neutrons. D. only electrons. 5. What is the most current model used to describe the structure of the atom? A. solar system model B. Bohr model C. solid sphere model D. electron cloud model 16 Chapter 1: Matter