2. All parts of a homogeneous mixture look the same, as in a solution. A heterogeneous mixture has two or more distinguishable parts, as in a mechanical mixture, or tiny particles of one substance held within another, as in a suspension.
4. (a) physical
12. Groups (or chemical families) in the periodic table are organized in columns, and periods are organized in rows. A group is an assortment of elements with similar properties. A period is a single row on the periodic table in which each successive element has one more proton per atom than the element to its left.
15. Students’ answers may vary but could include sodium or any other alkali metal.
16. (a) 1
17. (a) calcium
(b) Group 2, alkaline earth metals
20. A metal element is most likely to form an ion by losing electrons; it will form a positive ion.
21. (a) lithium (1) and chlorine (1)
(b) aluminum (2) and sulphur (3)
(c) silver (1) and fluorine (1)
(d) zinc (1) and oxygen (1)
(e) nitrogen (2) and sulphur (3)
(f) bromine (1)
22. (a) ionic compound
(b) ionic compound
(c) ionic compound
(d) ionic compound
(e) molecular compound
(f) neither (element)
23. Students’ answers may vary but could include symptoms of mercury poisoning such as impaired speech or memory loss.
29. Diamond is made of carbon only and so is considered an element.
30. We cannot dispose of all household waste in the same way because some substances may have harmful chemical properties. Examples may vary but could include car batteries, which need to be taken to special waste depots because they contain dangerously strong acids, and vinegar, which is also an acid but weak enough to pour down the sink.
32. (a) Students’ answers may vary but could include the fact that Groups 17 and 18 are both groups of non-metals or that both are gases at room temperature or slightly above room temperature.
(b) Group 17 elements are highly reactive, while Group 18 elements are inert.
33. (a) does not normally form ions
(d) does not normally form ions
(e) Pb2+ or Pb4+
36. (a) heterogeneous mixture
(c) solution (technically, suspension)
44. (a) The non-metal is X. (It has the properties of a halogen.)
(b) The alkali metal is Z. (It is a reactive solid.)
(c) The noble gas is Y. (It is an non-reactive gas.)
48. It would be safer to eat the fish at the bottom of the food chain, as the concentration of pollutants that bioaccumulate and biomagnify would be less than in a fish at the top of the food chain. This way, you would consume a smaller amount of dangerous pollutants such as heavy metals.
51. The sample shown is a purple-pink, somewhat dull, crystalline solid, with a lumpy texture. Students may add that cobalt(II) chloride is a salt and so has properties of an ionic compound, such as the ability to conduct electricity when dissolved in water.
52. If the test tube contained oxygen gas, the splint would relight when the glowing splint was inserted into it.
57.(a) magnesium bromide
(b) barium nitride
(c) calcium phosphide
(d) aluminum oxide
(e) sodium iodide
(f) calcium chloride
58.(a) ionic, Mg3P2
(b) ionic, Li3N
(c) molecular, PCl5
(d) ionic, AlBr3
(e) ionic, CaS
(f) molecular, SO2
(g) ionic, KI
(h) ionic, Na2O
(k) molecular, NCl3
60. You would know that the lemon juice reacted with copper if there were bubbles (gas produced), if the copper changed colour, or if heat was released or absorbed.
68. Students’ answers may vary but could include examples such as chemicals from batteries, lead paint, and motor oil. All three may leach into the water system from landfill, thus polluting the soil, water, and organisms that live in the area.
74. Students’ answers may vary but could include water, which is used for cleaning and cooking, or chalk (calcium carbonate), which is used as an antacid.