Section 2 1 The Nature of Matter (pages 35 39)

Transcription

1 Chapter 2 The Chemistry of Life Section 2 1 The Nature of Matter (pages 35 39) Key Concepts What three subatomic particles make up atoms? How are all of the isotopes of an element similar? What are the two main types of chemical bonds? Atoms (page 35) 1. The basic unit of matter is called a(an). 2. Describe the nucleus of an atom. 3. Complete the table about subatomic particles. SUBATOMIC PARTICLES Particle Charge Location in Atom Positive Neutral Negative 4. Why are atoms neutral despite having charged particles? Elements and Isotopes (page 36) 5. What is a chemical element? 6. What does an element s atomic number represent? 7. Atoms of the same element that differ in the number of neutrons they contain are known as. 8. How are isotopes identified? 9. Why do all isotopes of an element have the same chemical properties? 61

2 Chemical Compounds (page 37) 10. What is a chemical compound? 11. What does the formula for table salt indicate about that compound? Chemical Bonds (pages 38 39) 12. What holds atoms in compounds together? 13. Complete the table about the main types of chemical bonds. CHEMICAL BONDS Type Formed when... Covalent bond Ionic bond 14. What is an ion? 15. Is the following sentence true or false? An atom that loses electrons has a negative charge. 16. The structure that results when atoms are joined together by covalent bonds is called a(an). 17. Circle the letter of each sentence that is true about covalent bonds. a. When atoms share two electrons, it is called a double bond. b. In a water molecule, each hydrogen atom forms a single covalent bond. c. Atoms can share six electrons and form a triple bond. d. In a covalent bond, atoms share electrons. 18. The slight attractions that develop between oppositely charged regions of nearby molecules are called. 62

3 Protons, Neutrons, and Electrons The diagram shows a model of an atom. It shows the nucleus, protons, neutrons, and electrons. The diagram is not to scale. Label a proton, a neutron, an electron, and the nucleus. Then, color the protons green, the neutrons purple, and the electrons orange. Helium Atom Use the diagram to answer the questions. 1. What are the negatively charged electrons attracted to? 2. Which of the following describes the charge of a neutron? Circle the correct answer. positive negative no charge 50

4 Isotopes Isotopes are atoms of an element that have the same number of protons but a different number of neutrons. The number of protons plus the number of neutrons in an isotope is called its mass number. Carbon-12, for example, has 6 protons and 6 neutrons so its mass number is 12. Draw the correct number of protons and neutrons for each isotope. Indicate protons with a plus sign ( ). Write the number of protons and neutrons in each isotope. Isotopes of Carbon Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 electrons 6 electrons 6 protons protons protons 6 neutrons neutrons neutrons Use the diagram to answer the questions. 1. Name one difference between carbon-12 and carbon Name one way in which carbon-12 and carbon-14 are alike. 51

5 Ionic Bonds In an ionic bond, one atom transfers one or more electrons to another atom. The atom that loses the electron(s) becomes a positively charged ion. The atom that gains the electron(s) becomes a negatively charged ion. Count the electrons in each atom or ion. Write this number in the space provided. Then, determine the charge of the atom or ion. Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na + ) Chloride ion (Cl ) Transfer of electron Protons +11 Protons +17 Protons +11 Protons +17 Electrons 11 Electrons Electrons Electrons Charge 0 Charge Charge Charge Use the diagram to answer the questions. Circle the correct answer. 1. Which of these is negatively charged? sodium atom chloride ion 2. Which of these is positively charged? sodium ion chlorine atom 3. The diagram above shows the formation of sodium chloride. What kind of substance is sodium chloride? a compound an element 52

6 Covalent Bonds In a covalent bond, two atoms share electrons. The electrons move in the orbitals of both atoms. In a single covalent bond, they share two electrons. One oxygen atom can form single covalent bonds with two hydrogen atoms to make water. Color the electrons in the oxygen atom orange. Use purple to fill in the electrons in both hydrogen atoms. O H H Hydrogen Atoms In the water molecule circle the shared electrons. O H H Water Use the illustrations to answer the question. 1. What is the name of the structure formed when atoms are joined by covalent bonds? 53

7 Types of Molecules Living things need organic compounds called carbohydrates, lipids, nucleic acids, and proteins. Fill in the missing cells in the table. Identify the function of the molecule or the main components (types of atoms) that make up the molecule. The first row has been done for you. Type of Components of Function of Molecule Molecule Molecule carbohydrate carbon, hydrogen, main source of energy; and oxygen structural purposes lipid mostly carbon and hydrogen nucleic acid hydrogen, oxygen, nitrogen, carbon, and phosphorus protein controls rate of reactions; transports substances into or out of cell; fights disease Use the table to answer the question. 1. Which of the types of molecules in the table contain carbon? 54

8 Section 2 2 Properties of Water (pages 40 43) Key Concepts Why are water molecules polar? What are acidic solutions? What are basic solutions? The Water Molecule (pages 40 41) 1. Is the following sentence true or false? A water molecule is neutral. 2. Why is a water molecule polar? 3. Circle the letter of each sentence that is true about hydrogen bonds. a. A hydrogen bond is stronger than an ionic bond. b. The attraction between the hydrogen atom on one water molecule and the oxygen atom on another water molecule is an example. c. A hydrogen bond is stronger than a covalent bond. d. They are the strongest bonds that form between molecules. 4. Complete the table about forms of attraction. FORMS OF ATTRACTION Form of Attraction Definition Cohesion Adhesion Solutions and Suspensions (pages 41 42) 5. What is a mixture? 6. A mixture of two or more substances in which the molecules of the substances are evenly mixed is called a(an). 7. The greatest solvent in the world is. 8. What is a suspension? 63

9 9. Complete the table about substances in solutions. SUBSTANCES IN SOLUTIONS Substance Definition Saltwater Solution Solute Water Acids, Bases, and ph (pages 42 43) 10. Why is water neutral despite the production of hydrogen ions and hydroxide ions? 11. What does the ph scale indicate? 12. On the ph scale below, indicate which direction is increasingly acidic and which is increasingly basic. Neutral Bleach Soap Seawater Human blood Pure water Normal rainfall Lemon juice Stomach acid 13. How many more H + ions does a solution with a ph of 4 have than a solution with a ph of 5? 14. What is an acid? 15. Is the following sentence true or false? Strong bases have ph values ranging from 11 to What are buffers? 64

10 Section 2 3 Carbon Compounds (pages 44 48) Key Concept What are the functions of each group of organic compounds? The Chemistry of Carbon (page 44) 1. How many valence electrons does each carbon atom have? 2. What gives carbon the ability to form chains that are almost unlimited in length? Macromolecules (page 45) 3. Many of the molecules in living cells are so large that they are known as. 4. What is the process called by which macromolecules are formed? 5. When monomers join together, what do they form? 6. What are four groups of organic compounds found in living things? a. b. c. d. Carbohydrates (pages 45 46) 7. What atoms make up carbohydrates? 8. Circle the letter of each sentence that is true about carbohydrates. a. Starches and sugars are examples of carbohydrates. b. Living things use them as their main source of energy. c. The monomers in sugar polymers are starch molecules. d. Plants and some animals use them for strength and rigidity. 9. Single sugar molecules are also called. 10. Circle the letter of each monosaccharide. a. galactose c. glucose b. glycogen d. fructose 65

11 11. What are polysaccharides? 12. How do plants and animals store excess sugar? Lipids (pages 46 47) 13. What kinds of atoms are lipids mostly made of? 14. What are three common categories of lipids? a. b. c. 15. Many lipids are formed when a glycerol molecule combines with compounds called. 16. Circle the letter of each way that fats are used in living things. a. As parts of biological membranes b. To store energy c. To give plants rigidity d. As chemical messengers 17. Complete the table about lipids. LIPIDS Kind of Lipid Description Each carbon atom in a lipid s fatty acid chain is joined to another carbon atom by a single bond. Unsaturated A lipid s fatty acids contain more than one double bond. Nucleic Acids (page 47) 18. Nucleic acids contain what kinds of atoms? 19. The monomers that make up nucleic acids are known as. 20. A nucleotide consists of what three parts? 66

12 21. What is the function of nucleic acids in living things? 22. What are two kinds of nucleic acids? a. b. Proteins (pages 47 48) 23. Proteins contain what kinds of atoms? 24. Proteins are polymers of molecules called. 25. What are four roles that proteins play in living things? a. b. c. d. Reading Skill Practice You can often increase your understanding of what you ve read by making comparisons. A compare-and-contrast table helps you to do this. On a separate sheet of paper, make a table to compare the four groups of organic compounds you read about in Section 2 3. You might use the heads Elements, Functions, and Examples for your table. For more information about compare-and-contrast tables, see Organizing Information in Appendix A. 67

13 Types of Molecules Living things need organic compounds called carbohydrates, lipids, nucleic acids, and proteins. Fill in the missing cells in the table. Identify the function of the molecule or the main components (types of atoms) that make up the molecule. The first row has been done for you. Type of Components of Function of Molecule Molecule Molecule carbohydrate carbon, hydrogen, main source of energy; and oxygen structural purposes lipid mostly carbon and hydrogen nucleic acid hydrogen, oxygen, nitrogen, carbon, and phosphorus protein controls rate of reactions; transports substances into or out of cell; fights disease Use the table to answer the question. 1. Which of the types of molecules in the table contain carbon? 54

14 Section 2 4 Chemical Reactions and Enzymes (pages 49 53) Key Concepts What happens to chemical bonds during chemical reactions? How do energy changes affect whether a chemical reaction will occur? Why are enzymes important to living things? Chemical Reactions (page 49) 1. What is a chemical reaction? 2. In the space provided, write a definition for each of the terms Definition Reactants Products 3. Chemical reactions always involve changes in chemical. Energy in Reactions (page 50) 4. What is released or absorbed whenever chemical bonds form or are broken? 5. What do chemical reactions that absorb energy need to occur? 6. Chemists call the energy needed to get a reaction started the. 7. Complete the graph of an energy-releasing reaction by indicating where the energy of the reactants, the energy of the products, and the activation energy should appear. Energy-Releasing Reaction Energy Course of Reaction 68

15 Enzymes (pages 51 52) 8. What is a catalyst? 9. Proteins that act as biological catalysts are called. 10. What do enzymes do? 11. What is part of an enzyme s name usually derived from? Enzyme Action (pages 52 53) 12. The reactants of enzyme-catalyzed reactions are known as. 13. Why are the active site and the substrates in an enzyme-catalyzed reaction often compared to a lock and key? 14. The binding together of an enzyme and a substrate forms a(an). 15. How do most cells regulate the activity of enzymes? 69

16 Energy in Reactions The graphs below show the amount of energy present during two chemical reactions. The top graph has been labeled to show the reactants, products, and activation energy. Recall that activation energy is the energy needed to start a chemical reaction. Label the reactants and products on the bottom graph. Then, draw an arrow to show the activation energy. Energy-Absorbing Reaction Products Energy Reactants Activation energy Course of Reaction Energy-Releasing Reaction Energy Course of Reaction Use the graphs to answer the question. Circle the correct answer. 1. Which type of reaction often occurs spontaneously? energy-absorbing energy-releasing 55

17 Enzymes Many chemical reactions in cells take place on enzymes. The reactants bind to the enzyme until the reaction is complete. These reactants are called substrates. When the reaction is complete, the products are released. Enzyme Products Substrates 3 Active site 2 1 Use the diagram to place the steps below in the correct order. Products are released. Substrates bind to enzyme. Substrates are converted into products. Use the diagram to answer the questions. 1. Where do the reactants bind to the enzyme? 2. What is the function of enzymes in living things? Circle the correct answer. catalyze chemical reactions inhibit chemical reactions 56

18 Chapter 2 The Chemistry of Life Graphic Organizer Concept Map Using the information from the chapter, complete the concept map below. If there is not enough room in the concept map to write your answers, write them on a separate sheet of paper. Organic Compounds contain 1. Hydrogen 2. may also contain 3. consist of 4. Carbohydrates can be can be are made of units called Monosaccharides are linked by store genetic information in the form of function Peptide bonds

19

20

21

22

23

24

25