▲
▲
Fire dancing is a dangerous
art in which performers
manipulate burning
objects to create beautiful,
rhythmic patterns. The fire
is the main attraction in
the performance; it’s the
ever-changing movement
of light that keeps watchers
mesmerized. The dancer herself
is like a puppeteer who remains
obscured while creating the
effects. She does this not just by
controlling her movements but by
choosing the tools and fuel that
support the flames. In this way,
she controls the chemical reaction
that produces the light. Like all
chemical reactions, the one you see
here proceeds according to wellunderstood patterns determined
by the substances involved and the
conditions under which it occurs.
92
NS Science 10 CH3.indd 92
12/3/11 3:26:05 PM
Unit Contents
3
Chemical Names, Formulas,
and Equations
3.1 Ionic and Molecular
Compounds
3.2 Names and Formulas of Ionic
and Molecular Compounds
3.3 Chemical Equations and the
Law of Conservation of Mass
4
Classifying Compounds and
Chemical Reactions
4.1 Types of Chemical Reactions
4.2 Acids and Bases
4.3 Rates of Chemical Reactions
NS Science 10 CH3.indd 93
93
12/3/11 3:26:14 PM
What You Should Recall About...Physical and Chemical Properties
•
•
•
•
•
•
•
Properties of matter can be either physical or
chemical.
Physical properties are properties that do not
involve the way in which substances interact
chemically with other substances.
Chemical properties describe how substances
can change when they interact with other
substances to form new substances with new
properties.
Properties of matter can be either qualitative
or quantitative.
A qualitative property can be described
using words, such as “soft” and “red”; a
quantitative property can be described using a
measurement, for example, 100°C.
Examples of qualitative physical properties
include odour, colour, texture, state, and
malleability (the ability to be bent or
hammered without breaking).
Examples of quantitative physical properties
include melting point, boiling point,
solubility, and density.
Solubility describes how much of a
substance dissolves in another substance.
Check What You Recall
1. Window glass has a smooth texture. Brick
has a rough texture. Are these examples of
a physical property or a chemical property?
Explain your answer.
94
•
•
•
You can describe substances using their
physical properties just by observing them,
but chemical properties can only be observed
when substances interact in a chemical
change.
Some examples of chemical properties include
reactivity with other substances, such as water,
oxygen, or acids; and combustibility, the
ability of a substance to catch fire and burn
in air. Stability is another chemical property,
which refers to how easily the substance
breaks down to form other compounds.
Some examples of evidence that a chemical
change has taken place include the following:
• the formation of bubbles of gas when
baking powder and vinegar react
• the change in colour of a pair of blue jeans
that have been exposed to bleach
• the formation of a precipitate, such as the
formation of soap scum when soap and
minerals and water react, shown below
• the light and heat produced from a
campfire
• the sound of fireworks
Soap scum forms when soluble soap and soluble minerals in
water react to form a substance that does not dissolve in water.
2. Identify the types of properties described
in this sentence, and give reasons for your
choice: “Beeswax is soft and burns with a
bright flame.”
MHR • Unit 2 Chemical Reactions
NS Science 10 CH3.indd 94
12/3/11 3:26:19 PM
3. Decide whether each statement below
describes a physical property or a chemical
property of a substance. Then indicate
whether it is a qualitative property or a
quantitative property.
(a) It is a pale yellow gas at room
temperature.
(b) It can burn or etch glass permanently.
(c) Its density is 1.695 g/L.
(d) It explodes when it reacts with water.
(e) Its melting point is 0°C.
4. Which chemical property of propane would
be most important to keep in mind when
using a gas barbecue? Explain your answer.
5. Tetrafluoromethane is a compound that is
a potent greenhouse gas. It lasts for a long
time in the atmosphere because it does
not readily break down or react with other
substances. What chemical properties of
tetrafluoromethane are described here?
What You Should Recall About...Classifying Matter
•
•
•
•
Matter can be classified according to whether
it is a pure substance or a mixture.
According to the particle theory of matter,
pure substances contain only one type of
particle. They cannot be separated into other
substances by physical means.
According to the particle theory of matter,
mixtures contain more than one type of
particle. They can be separated into pure
substances by physical means.
Pure substances are either elements or
compounds. Elements cannot be broken
down further by physical or chemical means.
Compounds are composed of more than one
type of element and can be broken down into
elements by chemical means.
Check What You Recall
6. Classify the following materials as mixtures or
pure substances.
(a) soup
(d) carbon dioxide
(b) bronze
(e) air
(c) oxygen
(f) gasoline
7. Classify the following pure substances as
elements or compounds.
(a) carbon
(b) water
(c) silicon dioxide
(d) nitrogen
•
Mixtures contain more than one type of
element and/or compound. They can be
solutions, which are uniform throughout,
or mechanical mixtures, which have varying
composition throughout.
Matter
Mixtures
Mechanical
Mixtures
Pure Substances
Solutions
Elements
Compounds
Matter can be classified according to the categories shown here.
8. Saltwater is a solution that contains two pure
substances that happen to be compounds:
water and salt.
(a) Suggest a way you could get the salt from
the water.
(b) Is there a physical method by which
you could break down the salt or water
further? Explain your answer.
Unit 2 Preparation • MHR
NS Science 10 CH3.indd 95
95
12/3/11 3:26:21 PM
What You Should Recall About...Atomic Theory
•
•
A scientific law describes an action or pattern
observed so often that it is assumed to always
occur. For example, the law of conservation
of energy states that energy cannot be created
or destroyed, but can only change form.
A scientific theory is an idea or principle,
validated by scientists, that explains and
predicts events.
•
The atomic theory includes these ideas:
• All matter is composed of incredibly tiny
particles called atoms.
• Atoms cannot be created, destroyed, or
divided into smaller particles by a physical
or a chemical change.
• Atoms of different elements bond in
definite proportions to form compounds.
(c) Only a few investigations are conducted
before a theory is accepted by scientists.
10. During the Middle Ages, alchemists were
researchers who conducted investigations to
try to turn common metals such as lead into
gold. Why did alchemists fail to change lead
into gold?
Check What You Recall
9. Indicate whether the following statements are
true or false. If the statement is false, rewrite
it to make it true.
(a) In science, laws do not explain anything;
they just describe and summarize what
happens.
(b) A scientific theory rarely involves an
explanation of why something happens.
What You Should Recall About...Atoms and the Periodic Table
•
•
96
An atom is the smallest unit of an element
that has the properties of that element. Atoms
are made of even smaller subatomic particles:
protons, neutrons, and electrons.
The following statements are true for any
neutral atom:
• The number of protons is equal to the
number of electrons.
• The number of protons that an atom
of any element has is called the atomic
number.
• The sum of the number of protons and
the number of neutrons in an atom is
called the mass number.
• Protons and neutrons make up nearly all
the mass of an atom. Both neutrons and
protons have about 1840 times more mass
than electrons.
•
•
•
•
•
•
Chemical symbols, such as “B” for boron or
“Sn” for tin, are used to represent elements.
Chemical formulas are used to represent
compounds. For example, water is represented
by the formula H2O.
Elements are listed in the periodic table by
increasing order of atomic number. The
periodic law states that when elements are
arranged by atomic number, their chemical
and physical properties recur periodically.
A horizontal row in the periodic table is a
period. Periods are numbered from 1 to 7.
A vertical column in the periodic table is a
group. Groups are numbered from 1 to 18.
Elements in the same family (group) share
similar physical and chemical properties.
MHR • Unit 2 Chemical Reactions
NS Science 10 CH3.indd 96
12/3/11 3:26:23 PM
Check What You Recall
11. Copy and complete the following table.
Facts About Subatomic Particles
Electrons
Location
Protons
inside the
nucleus
Charge
Relative
size
Neutrons
positive ()
smallest
of these
particles
12. The atomic number for nitrogen is 7. How
many protons and electrons does an atom of
nitrogen have?
13. What is the chemical symbol for these
elements?
(a) gold
(d) argon
(b) aluminum
(e) silver
(c) antimony
14. What are the chemical symbols for the
following elements: helium, aluminum,
tungsten, cadmium, krypton, francium, cobalt,
and barium? (Refer to a periodic table.)
15. Which element is found in Group 3 and
Period 5 of the periodic table?
16. Only two elements are liquids at room
temperature. Which two are they? (Refer to a
periodic table.)
17. Which of the following is not a classification
of elements represented on the periodic table?
(a) solids, liquids, and gases
(b) metals, non-metals, and metalloids
(c) earth, water, and air
(d) natural elements and synthetic elements
18. List three elements found in Period 2 of the
periodic table.
19. List two elements found in Group 2 of the
periodic table.
20. The noble gases are the elements in Group
18 of the periodic table. These non-metals
are all odourless, colourless gases at room
temperature. Look at the periodic table
and then list the noble gases, including the
chemical symbol for each gas.
21. Identify the information listed below for the
element beryllium. Refer to the periodic table
below.
(a) symbol
(b) name of group
(c) number of protons
(d) number of electrons
(e) atomic number
Unit 2 Preparation • MHR
NS Science 10 CH3.indd 97
97
12/3/11 3:26:31 PM