UNIT. Review SUGGESTED ANSWERS WHAT DO YOU REMEMBER? 1. c. 2. a. 3. b. 4. c. 7. b. 6. c. 8. b. 5. c. 11. c. 12. d 13. True. 9. d. 10.

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1 UNIT C Review SUGGESTED ANSWERS WHAT DO YOU REMEMBER? 1. c 5. c 9. d 2. a 6. c 10. d 3. b 7. b 11. c 4. c 8. b 12. d 13. True 14. False. In a neutral atom, the number of electrons equals the number of protons. 15. False. The lustre of a substance is its shininess or dullness. 16. False. In a chemical change, a new substance is produced. 17. True 18. False. Metals are lustrous, ductile, and malleable. 19. True 20. False. Compounds can be broken down into simpler substances. 21. False. To determine the number of neutrons, subtract the atomic number from the mass number. 22. False. In Bohr s atomic model, the first electron orbit holds a maximum of 2 electrons. 23. True 24. True 25. True 26. mass 27. density 28. Workplace Hazardous Materials Information System. 29. wafting 30. physical 31. chemical 32. oxygen 33. vinegar 34. is table salt 35. J. J. Thomson 36. sulfur 37. decomposition 38. hydrogen NEL Unit C Review 431

2 39. limewater 40. (a) (iv); (b) (vii); (c) (i); (d) (viii); (e) (ii); (f) (iii); (g) (v); (h) (vi) 41. (a) (iii); (b) (iv); (c) (i); (d) (ii) 42. (a) (ii); (b) (iii); (c) (iv); (d) (v); (e) (i) 43. Sample answer: The batter has changed colour, holes in the cake indicate that bubbles of gas formed, and a mixture that was runny at room temperature is now solid at room temperature. 44. (a) Physical change. The droplets form due to condensation and changes of state do not produce new substances. (b) Physical change. The grinding changes the form of the wheat, but not the chemical identity of its constituents. (c) Chemical change. The sugar chars (forms carbon); the change of colour indicates a chemical change. (d) Physical change. None of the ingredients of the peanut butter, jelly, or bread undergo a change of chemical identity. (e) Chemical change. The production of heat indicates a chemical change. (f) Physical change. Neither the sugar nor the tea undergoes a change of chemical identity. (g) Physical change. The pieces of egg are made smaller and smaller, but do not undergo a change of chemical identity. 45. Formula Element Compound Atom Molecule H 2 O 2 No Yes No Yes Fe Yes No Yes No N 2 Yes No No Yes CH 4 No Yes No Yes O 3 Yes No No Yes 46. Element name Element symbol Atomic number Mass number Number of protons Number of neutrons Number of electrons potassium K tin Sn calcium Ca silicon Si fluorine F WHAT DO YOU UNDERSTAND? 47. Students diagrams will vary, but should reflect the following: Matter can be classified into two categories: mixtures and pure substances. Mixtures can be further categorized as solutions or mechanical mixtures. 48. Alloys are mixtures of metals; the individual metals in alloys do not chemically combine. 49. Sample answer: Two elements found in most kitchens are aluminum and copper; two compounds found in kitchens are table salt (NaCl) and drain cleaner (sodium hydroxide); two mechanical mixtures found in kitchens breakfast cereals and granola bars. 50. (a) Air is a solution made up primarily of nitrogen, oxygen, and carbon dioxide (b) Salt water is an example of a solution formed by a solid dissolving in a liquid. (c) Clear apple juice is an example of a liquid solution. 432 Unit C: Atoms, Elements, and Compounds NEL

3 51. (a) Quantitative properties give numerical information about a substance; qualitative properties do not provide numerical information. (b) Colour and texture are qualitative properties; temperature and mass are quantitative properties. (c) Optical clarity can be described qualitatively with words, such as transparent, translucent, or opaque, it can also be described quantitatively by expressing the percentage of light that passes through an object. 52. Compound Types of Elements (metal/non-metal) Type of Compound NaCL metal and non-metal ionic CO 2 non-metals molecular KF metal and non-metal ionic SO 2 non-metals covalent CaO metal and non-metal ionic 53. This definition is incomplete, because some matter cannot be seen or touched. 54. The mass number is always equal to or greater than the atomic number. The mass number includes both protons and neutrons, whereas the atomic number only includes protons. 55. (a) (b) (c) 18p 22n 0 15p 16n 0 1p 0n The new element should have a relatively low melting point, density, and hardness, but good electrical and thermal conductivity as well as a shiny lustre when freshly cut or polished. It should have only one electron in its outermost orbit, and should react with water. 57. All of the elements in the alkaline earth metals have two electrons in their outermost orbit. Each element, however, has a different number of orbits. Beryllium, for example, has two orbits, whereas magnesium has three orbits. 58. In the second period, all of the elements have two orbits for electrons. Each element, though, has a different number of electrons in the second orbit. Boron, for example, has three electrons in its second orbit, whereas carbon has four. 59. There are more metals. Many more elements lie to the left of the line that separates metals from non-metals. 60. (a) The fact that ice is less dense than liquid water is unusual, because for most substances, the solid form is more dense than the liquid state. (b) If ice sank to the bottom of ponds in winter, the pond water would freeze from the bottom up, trapping fish and other organisms in solid ice, likely killing them. (c) When liquid water turns to ice, the molecules spread out somewhat, making the density lower, and the ice floats like the iceberg that sank the Titanic. If water freezes in cottage pipes or glass bottles, it expands with such force that it can break the pipes or bottles. 61. Each of these processes is a chemical change involving, in part, oxygen atoms. Reactive oxygen atoms in hydrogen peroxide can lighten the colour of materials; oxygen atoms combining with hydrogen and carbon atoms cause combustion; and oxygen atoms combining with iron atoms cause rusting. The rate at which these reactions occurs differs. Rusting is a slow reactions, bleaching is somewhat quicker, and burning is a very quick reaction. NEL Unit C Review 433

4 62. (a) Check that students have correctly rolled their cylinders. Model for students if necessary. Have students place their finger on hydrogen, and then trace the elements by increasing atomic number. (b) The elements naturally flow from one to the next, so in some ways a cylinder is more logical, and a spiral might be even more logical than a cylinder. (c) Elements properties change gradually except when going from a noble gas to an alkali metal, at which point properties suddenly jump to much higher or lower values. In a cylinder periodic table, putting the alkali metals right next to the noble gases does not suggest that properties will jump, which is less logical than the regular periodic table. 63. Bohr-Rutherford diagrams of potassium and chlorine: 19p 20n 0 17p 18n 0 K Cl (a) Chlorine can gain one more electron to fill its outer orbit and have an electron arrangement like that of argon. Potassium has one electron in its outermost orbit; by giving this electron away, its electrons will be arranged like those in argon. (b) If a potassium atom collides with a chlorine atom, the potassium s lone outer electron can be transferred to the chlorine atom to make each atom have an electron arrangement like argon and thus be stable. The potassium atom becomes a 11 ion and the chlorine atom becomes a -1 ion and their opposite charges hold them together to form an ionic compound. SOLVE A PROBLEM 64. (a) Sample answer: To determine if a substance is a metal, I would check the following: I would check to see if it is shiny (metals are shiny). I would check to see that it conducts electricity. I would also check to see if it is malleable. (b) Sample answer: To determine the element s identity, I would determine its mass and volume by measuring. I would then use this information to calculate the sample s density. Density is a characteristic property; I can use this to determine the specific element. 65. The information that silver and gold are found in pure form leads me to believe that they are not very reactive; a more reactive substance would react with other substances and not be found in pure form. 66. (a) The density of the wood before and after cutting stays the same, (b) This could be tested by measuring the mass and volume of wood before cutting and then the mass and volume of a piece of wood after cutting. Using the mass and volume; the densities can be compared. 67. Halogen lamps generally have a smaller quartz bulb inside an outer glass envelope. There is a small amount of bromine or iodine inside the quartz bulb, so care should be taken not to break it during disposal, thus releasing the halogen (although the amount is not really dangerous). The bigger problem is that some halogen lamps have lead solder and, if so, must be treated as hazardous waste. 68. Coal that is burned in power plants and boilers is a major source of mercury pollution. Waste incinerators also produce mercury from mercury-containing products in the waste. Internationally, industry also continues to cause mercury pollution. Using less energy, supporting the use of low-mercury coal and accepting the cost of cleaning coal are ways to help mercury pollution. Mercury accumulates in living things and is very toxic, attacking the central nervous system and other tissues. 434 Unit C: Atoms, Elements, and Compounds NEL

5 CREATE AND EVALUATE 69. (a) Answers will vary, but should focus on major safety rules such as wearing goggles, gloves, and aprons, following instructions carefully, and alerting the instructor when spills happen. (b) Answers will depend on the layout of the classroom. (c) Students explanations and drawings should match what is shown in Figure 2 on page 601 of the Student Book. 70. The first discoveries that showed atoms had smaller particles inside could not have happened without the invention of cathode ray tubes, an example of technology leading to improvements in atomic theory. Better theories can also lead to better technology. For example, our understanding of how electrons behave in atoms allows us to design molecules on computers for a specific purpose, thus avoiding many trial and error experiments. 71. Mining in Northern Ontario Benefits Creates jobs Stimulates local economy Stresses Environmental pollution Directly harm to people 72. (a) ductility (b) To demonstrate malleability, one could hammer a piece of solder and show that it can be pounded flat without breaking or shearing. To demonstrate electrical conductivity, one could include a length of solder in a simple circuit of a small light bulb connected to a battery. (c) Both tin and bismuth have relatively low melting points as pure metals, which is reflected to a degree in the very low melting point of the solder they form. In 10 kt gold jewelry, the colour of the gold may still be somewhat visible, although other metals in the alloy can greatly influence the colour as well. (d) In sodium chloride, the properties of the sodium and chlorine are very different than when they are pure elements. You can eat table salt, but pure sodium would explode in your mouth and pure chlorine would poison you. 73. Review students logs to look for correctly identified examples of compounds and mixtures used in the art project. Remind students that their artwork should relate to the information presented in the unit. 74. (a) Solid B is most likely a compound because it decomposed into a gas and a powder. (b) Solid A is most likely an element because it simply changed state. (c) A physical test that could be done would be to continue heating the liquid and observe the boiling point. 75. (a) A chemical test that could be used to test which gas is oxygen is the burning splint test. If the gas is oxygen a burning splint will burn more vigorously. If the gas is hydrogen, there will be a popping sound. (b) It is impossible for one of the gases to be carbon dioxide because carbon atoms are not present in water. 76. The eagle will likely have the most toxins in its tissues because toxins do not break down and thus bioamplify as you move up the food chain. REFLECT ON YOUR LEARNING 77. Sample answer: The periodic table is amazing because such a simple organization of the elements summarizes a very large number of patterns in their properties. 78. Sample answer: The periodic table is difficult to use because the patterns are not perfect. NEL Unit C Review 435

6 79. Sample answers include using billiard ball, plum pudding, and solar system to describe atoms and using quark to describe particles inside of protons and neutrons (Murray Gell-Mann named these particles quarks after a line from Finnegan s Wake by James Joyce: Three quarks for Muster Mark! ). 80. Sample answer: I would want my favourite sweater to be durable, so I could wear it many times over a long time period. However, this would be a problem when I was done with the sweater, because it would not break down in the landfill. 81. Sample answer: Chemistry is called the central science, because all particles, matter and their interactions are central to the workings of all areas of science. 82. Sample answer: Understanding the properties of matter helps me make consumer decisions that are good for the environment. I also can study matter to understand environmental issues such as pollution. WEB CONNECTIONS 83. (a) Water is very stable, so when hydrogen and oxygen combine to form water, a great deal of energy is released, making them a good fuel. (b) The main safety problem with hydrogen is its flammability. It ignites so easily that it must be kept away from sparks, hot objects and open flames. Leaking tanks are especially dangerous because hydrogen fully mixed with air can be explosive! 84. Answers will vary depending on the natural substance chosen by each student. Teacher should check the following: each students has chosen a naturally occurring compound to research; students has identified how the substance harms the environment or human health; students identifies at least one way the effects of the substance can be controlled. 85. Answers will vary. Students should examine the issue of the spread of pesticides through the food chain, including toxic materials being carried far from their sources by migrating animals. 436 Unit C: Atoms, Elements, and Compounds NEL