Chapter 2: The Chemical Context of Life

Transcription

1 AP Biology Guided Reading Name Chapter 2: The Chemical Context of Life Concept 2.1 Matter consists of chemical elements in pure form and in combinations called compounds 1. What is the difference between an element and a compound? 2. What four elements make up 96% of all living matter? 3. What is the difference between an essential element and a trace element? Concept 2.2 An element s properties depend on the structure of its atoms 4. Sketch a model of an atom of helium, labeling the electrons, protons, neutrons, and atomic nucleus. 5. Fill in the table about the subatomic particles. Subatomic particle Charge Location in an atom Mass Proton Neutron Electron 6. What is the difference between the atomic number and the atomic mass of an atom? 7. How would you identify the number of protons and neutrons of an atom? 8. Identify the atomic number, atomic mass, and the numbers of subatomic particles using the diagram below. 32 S Atomic # Atomic mass 16 Protons Neutrons Electrons 1

2 9. Identify the atomic number, atomic mass, and the numbers of subatomic particles using the periodic table entry below. 12 Mg Atomic # Atomic mass Protons Neutrons Electrons 10. What is an isotope and what do all isotopes of the same element have in common? 11. Explain why atomic masses on the periodic table are written as decimals and not whole numbers. 12. Which is the only subatomic particle that is directly involved in the chemical reactions between atoms? 13. Define energy and then explain what it means to have potential energy? 14. Explain which has more potential energy in each pair: a. boy at the top of a slide/boy at the bottom b. electron in the first energy shell/electron in the third energy shell c. water/glucose 15. Label the electron shells to the right by indicating which shell has the least amount of energy and which has the most. 16. Explain what must happen in order for an electron to jump from shell 1 to shell 2 or shell 1 to shell 3. Provide an example. 17. Explain what must happen in order for an electron to jump from shell 3 to shell 2 or shell 3 to shell 1. Provide an example. 18. Explain what is happing at an atomic level when object feels warm to the touch. What about cool to the touch? 2

3 19. What determines the chemical behavior of an atom? 20. Here is an electron distribution diagram for sodium: a. How many valence electrons does it have? Sodium 11Na b. Circle the valence electron(s). c. How many protons does it have? Concept 2.3 The formation and function of molecules depend on chemical bonding between atoms 21. Define covalent bond. 22. Refer back to the definition of a compound and explain the difference between a compound and a molecule? 23. Now, fill in the following chart: Water Methane Oxygen Molecule? (y/n) Compound? (y/n) Molecular Formula Structural Formula Carbon dioxide 24. Refer back to the structural formula for oxygen. What type of bond is seen in O 2? Explain what this means. 25. Draw the structural formula for sulfur if it were exposed to hydrogens. 26. Define valence. 27. What is the difference between the terms valence and valence electrons? 28. Identify the valence of the following atoms: a. Hydrogen b. Nitrogen c. Chlorine d. Sulfur 29. To the right, draw an electron distribution diagram for an atom with a valence of 2. Careful: refer back to the definition for valence. How many valence electrons does your diagram have? 3

4 30. What is meant by electronegativity? 31. Explain the difference between a nonpolar covalent bond and a polar covalent bond. 32. Draw an electron distribution diagram of water to the right, and then answer the following. (This is a very important concept. Spend some time with this one!) a. Which element is more electronegative? b. Why is water considered a polar molecule? c. Label the regions that are more positive or more negative. 33. Another bond type is the ionic bond. a. Explain what is happening in regards to electrons in the figure to the right (Figure 2.14). b. What two elements are involved? c. Which of the two elements is more electronegative? Explain. 34. What is the difference between an anion and a cation? 35. How can you determine if an ion is an anion or a cation? In the ionic bond example above, which is the anion? Explain. 36. Compare the strengths of the ionic bonds in grains of salt sitting on your dining room table to those of salt water. Explain. 37. What is a hydrogen bond? Indicate where the hydrogen bond occurs in the figure to the right. 4

5 38. Explain van der Waals interactions. Though they represent very weak attractions, when these interactions are numerous they can stick a gecko to the ceiling! 39. Here is a list of the types of bonds and interactions discussed in this section. Place them in order from the strongest to the weakest: hydrogen bonds, van der Waals interactions, covalent bonds, and ionic bonds when dry. STRONGEST WEAKEST 40. The function of a molecule is related to its. Concept 2.4 Chemical reactions make and break chemical bonds 41. Write the chemical shorthand equation for photosynthesis. Label the reactants and the products. 42. For the equation you just wrote, how many molecules of carbon dioxide are there? How many molecules of glucose? How many elements in glucose? How many molecules of carbon dioxide would be needed to produce 3 glucose molecules? 43. What is meant by dynamic equilibrium? Does this imply equal concentrations of each reactant and product? Explain. 5