Key Concept Review (Pg 164)
1. A pure substance is made up of one type of element or compound,while a mixture contains two or more pure substances that are notchemically combined. Examples of pure substances are potassium (oranother element) and water (or another compound). Students maygive any solution, suspension, or mechanical mixture as an exampleof a mixture; examples include salt water, salad dressing, and aneedle in a haystack.
2. A chemical change is a process, or change in matter, that results inthe formation of a new substance or substances.
3. (a) solid gas = sublimation
(b) solid liquid = melting
(c) liquid gas = evaporation
(d) liquid solid = freezing (or solidification)
(e) gas liquid = condensation
(f) gas solid = deposition (sometimes called sublimation)
4
Connect Your Understanding
10. (a) Leaves changing colour suggests a chemical change, as a new substance is formed.
(b) A precipitate forming suggests a chemical change, as a new substance is formed.
(c) Water boiling is a physical change, as it is simply a change of state.
11. Water forms droplets on a smooth surface, such as a countertop, due
to lack of adhesion between the water and the surface and cohesion of
the water to itself; particles in the water attract one another and stick
together.
12. The following are examples of different types of mixtures with
different arrangements of parts.
(a) A drink made by dissolving drink crystals in water is a solution
(homogeneous mixture).
(b) A cup of tea with leaves in it is a mechanical mixture
(heterogeneous mixture).
(c) Tomato juice is a suspension (heterogeneous mixture).
13. Many substances will undergo a chemical reaction if heated.
Examples may vary but could include paper, which will burn with
sufficient heating, and baking powder, which releases carbon dioxide
gas when heated.
Key Concept Review (Pg 206)
1. The smallest amount of an element that can exist is an atom.
2.
Particle / Charge / Location in Atom / Relative Masselectron / 1− / shells or energy levels / tiny (1)
neutron / 0 / nucleus / huge (1837)
3. 2, 8, 8
4. Students should list three of the halogens (fluorine, chlorine,
bromine, and iodine). Students’ answers to the second part of the
question may vary but could include a shared property such as having
noticeable colours or being very reactive.
5. (a) plumbum
(b) Pb
6. Students’ answers may vary but could include carbon, phosphorus,
sulphur, and selenium.
7. An insulator does not allow the flow of electrons or heat. A conductor
does. Silicon is an example of a weak conductor.
8. (a) technetium
(b) dysprosium
9. (a) 4
(b) 2
(c) helium
10.
11.(a) The fact that mercury is shiny and silver in colour probably led
early chemists to classify it as a metal.
(b) Unlike most metals, mercury is liquid at room temperature.
12. (a) In general, the number of protons (or atomic number) and atomic
mass increases steadily from the first element in the periodic table
to the last.
(b) Yes, there are some exceptions to this pattern: in a few cases,
atomic mass does not increase from one element to the next.
5 Pages 206–207
108 Unit B: Atoms, Elements, and Compounds
Connect Your Understanding
13. Students’ answers may vary but could include the following: People
have known about gold since ancient times when Latin was spoken.
Since aurum was the Latin term for gold, it made sense to assign the
symbol Au to gold, and not worth the effort or confusion to change
the symbol to Go, which is a word in its own right.
14. Mendeleev placed the elements in his periodic table in order of
increasing mass of their atoms, while at the same time grouping them
according to their properties.
15. (a) Diamond is made of carbon. Carbon also occurs in pure form as
graphite or coal; students need to give only one example.
(b) Students’ answers may vary but could include burning coal for
energy, using graphite for pencils, and making jewellery out of
diamonds.
(c) Some of the environmental issues relating to the use of carbon are
those associated with mining; also, burning coal produces air
pollution and greenhouse gases that can contribute to climate
change.
16. (a) Students’ answers may vary. For example: I would use silicon
(Si) and/or tin (Sn) to predict the properties of Mendeleev’s new
element as they are in the same column in the figure. Elements in
the same column in the modern periodic table (or same row of
Mendeleev's table) have the same properties.
(b) Students’ answers may vary but could include any estimate
between the atomic mass of gallium (69.72 amu) and arsenic
(74.92 amu).
(c) Students’ answers may vary but could include any shade between
light grey to dark grey.
(d) germanium
(e) Mendeleev did not predict an atomic number for eka-silicon
because the concept of protons did not yet exist.
17. Students’ answers may vary but could include advances in
technology, the discovery of subatomic particles such as protons, and
developments in atomic theory.
18. New elements created in a lab have many more subatomic particles
than most common elements, such as iron. These new elements have
high atomic numbers, since all the lower atomic number elements
have been accounted for.
19. Students’ answers may vary but could include a poster or
announcement about the danger of adding sodium to water or
allowing sulphur to react with air.