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Activity 2 What’s the Evidence?
INTERACTIONS AND CLASSIFYING MATERIALS
Activity 2: What’s the Evidence?
1. The evidence of a physical interaction is a change in
a) both the physical properties and the chemical properties of an object.
b) the physical properties of an object, but no change in its chemical properties.
c) the chemical properties of an object, but no change in its physical properties.
d) either the physical or the chemical properties; it doesn’t matter which.
e) none of the above.
2. Which of the following is a physical property of a substance?
a) The melting temperature is – 70ºC.
b) It does not interact with vinegar.
c) It interacts with BTB (color change from blue to yellow).
d) It is not flammable (does not burn).
e) It interacts with baking soda to produce bubbles of a gas.
3. The clues can fool you! The evidence for a chemical reaction can be the same as
the evidence for physical interactions. The clues fooled the following two students.
You be the teacher and explain why each student’s conclusion is wrong.
a) Student 1: “The repeated freezing and thawing of water in the cracks in
rocks causes the rocks to break up. This is evidence that a chemical reaction
has occurred.”
b) Student 2: “A light bulb gives off heat and light. A chemical reaction must
be occurring in the light bulb.”
4. Sugar dissolves in tea, making the tea taste sweeter. When the solution is boiled,
sugar is one of the substances left in the container. Do you think this example of
dissolving is a chemical interaction or a physical interaction? Justify your answer
in terms of whether the dissolving interaction is reversible.
5. When vinegar (acetic acid) is added to baking soda (sodium bicarbonate), the
baking soda dissolves in the vinegar, producing carbon dioxide gas, sodium
acetate, and water. When the carbon dioxide gas is mixed with the sodium acetate
solution, the original acetic acid and baking soda are not produced. When the
mixture is condensed to solids or boiled to gases, the original acetic acid and
baking soda are not produced. Is this an example of dissolving a reversible
interaction? Justify your answer.
Unit 5 • Chapter 2
Activity 2 Practice
1. (b)
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2. (a)
3. (a) The interaction with the water
and rocks does not result in new
materials, so there is no chemical
reaction in these substances. In
the absence of a chemical
reaction, the rocks breaking up
must be evidence of a physical
interaction. (The phase change of
water and the rocks breaking into
pieces are both physical
interactions.)
5
5. Dissolving baking soda in vinegar
is not a reversible interaction. My
evidence is when the products of
this reaction (sodium acetate and
carbon dioxide) are mixed, they
do not form the original reactants
(sodium bicarbonate and acetic
acid), and a phase change
(physical interaction) in the
product solution does not yield
the original reactants (sodium
bicarbonate and acetic acid).
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(b) The interaction in the light
bulb does not result in a new
material, so there is no chemical
reaction in the light bulb. In the
absence of a chemical reaction,
the light bulb giving off heat and
light is evidence of physical
(infrared and light) interactions.
4. Dissolving sugar in tea is a
reversible interaction because
another physical interaction
(boiling the solution) can be used
to get the original sugar back.
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Activity 3 Practice
1. (a)
2. The water will evaporate the
fastest from container (E), which
has the greatest surface area (22
square units) of water exposed to
the air. My evidence is we
observed in the experiment the
container with the greatest
exposed surface area had the
most water evaporate from it.
Activity 3: Investigating Evaporation
1. Which of the following variables has no influence of the evaporation rate of water?
a) The amount of water in identical containers.
b) The surface is of the water open to the air.
c) Whether on not water is heated by an energy source (such as the sun or a
heat lamp).
d) Whether a container of water is open or closed (sealed).
Imagine that you are looking down on five containers with the same volume of water,
as shown in the diagram below. Questions 2 through 4 refer to this diagram.
top view of water containers
3. The water will evaporate the
slowest from container (C), which
has the least surface area (14
square units) of water exposed to
the air.
A
E
D
4. The water will evaporate at the
same rate from containers (B) and
(D), since they have the same
surface area (18 square units) of
water exposed to the air.
2. From which container (A, B, C, D, or E) will the water evaporate the fastest? Justify
your answer.
3. From which container will the water evaporate the slowest? Justify your answer.
4. From which two containers will the evaporation rate be the same? Justify
your answer.
5. Shawn and Ben were thirsty. Shawn poured water into two identical glasses, and
took them to the basement where they were studying. Ben left his glass in a sunny
windowsill. Shawn left his glass on a table far from the window. They were so busy
they forgot to drink the water. Five days later when they returned to the basement,
who has the most water left in the glass? Justify your answer.
5. I would expect Shawn’s unheated
glass to have more water
remaining in it than Ben’s glass,
which was heated in the Sun. My
evidence is that heated water
evaporated more quickly than the
unheated water in the experiment.
6. Two sisters, Maria and Isabel, fill two fish bowls with the same amount of water.
Isobel seals her fish bowl with plastic wrap to keep the dust out. Five days later,
they come home from the pet store with their fish. Whose fish bowl has the most
water left? Justify your answer.
Maria’s bowl
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Isabel’s bowl
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6. Isobel’s sealed fish bowl has more
water left than Maria’s unsealed
fish bowl. In the experiment, we
saw that sealing a container
significantly reduced the amount
of water that evaporates.
C
B
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Activity 4 Mixture or Single Substance?
INTERACTIONS AND CLASSIFYING MATERIALS
Activity 4: Mixture or Single Substance?
Mixture or Single Substance?
1. An unknown, brown solid material was melted and then allowed to cool. It did not
separate into different substances. Is the unknown material a solution (mixture) or
a chemical (single substance)?
2. An unknown blue liquid was boiled. A blue solid was left after the liquid boiled
away. Is the unknown material a solution (mixture) or a chemical (single substance)?
The Language of Phase Changes
There are a number of different words to describe phase changes. Some of these
words are shown in the diagram. Many of the words describing phase changes are
opposites. For example,
vaporization, evaporation,
HEATING
and boiling (change from
changes to
changes to
liquid to gas) are opposite to
liquefaction
vaporization
condensation (change from
melting
evaporation
gas to liquid).
SOLID
LIQUID
boiling
3. Use the diagram of phase
changes at the right to help
you complete the table
below. Match each phase
change in the first column
with one of the descriptions
in the second column.
freezing
crystallization
solidification
GAS
condensation
changes to
changes to
COOLING
Phase
change
Description
A. solidification
1. After a cool night in the summer, the water vapor in the air
turns into small water droplets called dew.
B. boiling
2. Solder is a metal alloy (mixture of metals) that is useful because it
changes into a liquid at a lower temperature than most metals.
C. freezing
3. As the lava from a volcano cools, it turns into a solid.
D. evaporation
4. After a summer rain, a puddle gradually disappears.
E. liquefaction
5. When air is cooled to -218°C, the oxygen in the air
becomes a liquid.
F. vaporization
6. As the chocolate candy mixture is heated, it bubbles over.
G. melting
7. The water put in the freezer hardens into ice cubes.
H. condensation
8. A meteorite hitting the ocean could produce enough heat to turn
large amounts of water into water vapor very rapidly.
Unit 5 • Chapter 2
© It’s About Time
Phase
Change
5
PRACTICES—ANSWERS
MATERIALS AND THEIR INTERACTIONS
Activity 4 Practice
1. The unknown solid is a chemical
(single substance) because it did
not separate into different
substances during a phase
change.
2. I think the unknown liquid is a
solution (mixture) because it
separated into different
substances during a phase
change.
3. (see chart below)
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Description
a. solidification
3. As the lava from a volcano cools, it turns into a solid.
b. boiling
6. As the chocolate candy mixture was heated, it bubbled over.
c. freezing
7. The water put in the freezer hardens into ice cubes.
d. evaporation
4. After a summer rain, the puddle gradually disappeared.
e. liquefaction
5. When air is cooled to –218°C, the oxygen in the air becomes a liquid.
f. vaporization
8. A meteorite hitting the ocean could produce enough heat to turn
large amounts of water into water vapor very rapidly.
g. melting
2. Solder is a metal alloy (mixture of metals) that is useful because
it changes into a liquid at a lower temperature than most metals.
h. condensation
1. After a cool night in the summer, the water vapor in the air turned
into small water droplets called dew.
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CHAPTER 2 INTERACTIONS AND CLASSIFYING MATERIALS
Activity 5 Practice
1. (a) False. Compounds can be
broken down into simpler
substances during chemical
interactions.
Activity 5: Element or Compound?
1. Which statements below are true (T) and which are false (F)? If the statement is
false, change the underlined words to make it true.
(b) True.
A. Compounds can be broken down into simpler substances during physical
interactions.
(c) False. There are more
compounds than elements.
B. The simplest type of single substances (chemical) is elements.
C. There are more elements than compounds.
D. Very few of the 92 elements on Earth are found in nature (by themselves,
not in compounds).
(d) True.
2. Nonmetals
2. (b)
a) are the best conductors of electric current.
3. (e)
b) can be solid, liquid, or gas at room temperature.
c) can be shaped by pounding and hammering.
4. (a) The original yellow powder is
a compound, because when it is
heated, it breaks down into two
solids with different chemical
properties.
d) have medium to high densities.
e) are the best conductors of heat energy.
3. Which is the correct list of the physical properties of metals?
a) shine brightly when polished; good conductors of heat and electric current; solid
at room temperatures; tend to have low melting temperatures and densities;
can be shaped by pounding/hammering.
(b) The two solids are elements,
because neither solid can be
broken down into simpler
substances in chemical reactions.
b) good conductors of heat and electric current; solid at room temperatures; do
not shine at all when polished; tend to have medium to high melting
temperatures and density; can be shaped by pounding/hammering.
(c) The solid that is hard, gray,
shiny, and a good conductor of
electric current has the properties
of a metal, and the solid that is
dark purple, brittle, and a poor
conductor of electric current has
the properties of a nonmetal.
d) shine brightly when polished; good conductors of heat and electric current; solid
at room temperatures; tend to have medium to high melting temperatures and
density; are brittle and break when hammered.
c) bad conductors of electric current and heat energy; solid at room temperatures;
shine brightly when polished; tend to have medium to high melting
temperatures and density; can be shaped by pounding/hammering.
e) shine brightly when polished; good conductors of heat and electric current; solid
at room temperatures; tend to have medium to high melting temperatures and
density; can be shaped by pounding/hammering.
4. When a yellow powder is gently heated, it breaks down into two solids. One solid is
hard, gray, shiny, and a good conductor of electric current. The other solid is dark
purple, brittle, and a poor conductor of electric current. Neither solid can be broken
down into simpler substances in chemical reactions.
Answer the following questions.
a) Is the original yellow powder an element or a compound? Justify your answer.
b) Are the two solids produced elements or compounds? Justify your answer.
c) Do you think the solids produced are both metals, both nonmetals, or is one a
metal and the other a nonmetal? Justify your answer.
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Activity 6 The Periodic Table of Elements
INTERACTIONS AND CLASSIFYING MATERIALS
Activity 6: The Periodic Table of Elements
(Questions 1-3) Refer to the six diagrams of the Periodic Table shown below.
(a)
(d)
(c)
(b)
(e)
(f)
1. Which Periodic Table (a, b, c, d, e, or f) shows the location of the metalloids?
2. Which Periodic Table shows the location of the nonmetals?
3. Which Periodic Table shows the location of the noble gases?
4. This table shows the percentage, by mass, of
elements in the Earth’s crust. Most of these
elements are found in compounds.
Table
Element
Symbol
% Crust
a) Use the Periodic Table to find the symbol for
each element listed in the first column.
aluminum
8.1
calcium
3.6
b) Name (list) the eight most abundant elements
that make up more than 1% of the
Earth’s crust.
hydrogen
0.1
iron
5.0
5. Metalloids
a) shine the most.
b) are the best conductors of electric current.
c) are used in making semiconductors.
d) are the best conductors of heat energy.
e) have the lowest melting temperatures.
2.1
magnesium
oxygen
46.7
potassium
2.6
silicon
27.8
sodium
2.8
titanium
0.4
others (all)
0.8
TOTAL
5
PRACTICES—ANSWERS
MATERIALS AND THEIR INTERACTIONS
Activity 6 Practice
1. Periodic Table (D) shows the
location of the metalloids.
2. Periodic Table (E) shows the
location of the nonmetals.
3. Periodic Table (B) shows the
location of the noble gases.
4. (a)
Table
Element
Symbol
% Crust
aluminum
Al
8.1
calcium
Ca
3.6
hydrogen
H
0.1
iron
Fe
5.0
magnesium
Mg
2.1
oxygen
O
46.7
potassium
K
2.6
silicon
Si
27.8
sodium
Na
2.8
titanium
Ti
0.4
Others (all)
—
0.8
Total
100.0
100.0
(b) oxygen, silicon, aluminum, iron,
calcium, sodium, potassium,
magnesium
5. (c)
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Activity 7 Practice
1. (d)
2. (b)
Activity 7: Interactions and Classifying Materials
3. (b)
Multiple Choice
4. (c)
1. Which of the following is a physical property of a substance?
a) It does not interact with baking soda.
5. (a)
b) It is not flammable (does not burn).
c) It does interact with vinegar.
d) Its melting temperature is –78ºC.
e) It interacts with BTB (color change from yellow to blue).
2. According to its makeup (composition), matter can be classified as
a) solids, liquids, and gases.
b) elements, compounds, and mixtures.
c) acids, neutrals, bases, and salts.
d) metals, metalloids, nonmetals, and noble gases.
e) carbohydrates, proteins, and fats.
3. A single substance (chemical) that breaks down into other substances during
chemical reactions is
a) a solution.
b) a compound.
c) a nonmetal.
d) a metal.
e) a metalloid.
4. A single substance (chemical) that cannot be broken down into simpler
substances is
a) a suspension.
b) a solution.
c) an element.
d) a compound.
e) an acid.
5. Which of the following statements about the noble gases is not true?
a) They are chemically reactive and unstable.
b) They are colorless and transparent.
c) They are odorless.
d) They have very low melting temperatures.
e) They have low densities.
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Activity 8 Analyze and Explain
INTERACTIONS AND CLASSIFYING MATERIALS
Activity 8: Analyze and Explain
1. The scene of a crime was an old warehouse. The forensic scientists found some
shiny, round pellets near the window where the criminals escaped. When tested,
each pellet proved to be a good conductor of both electric current and heat energy.
a) Do you think the pellets are metallic or nonmetallic? Justify your answer.
b) Some of the pellets were heated until they melted. The material separated into
two different substances. Do you think the pellets are a mixture of two metals
(alloy) or an element? Justify your answer.
2. The table below lists several objects that could be part of a physical or chemical
interaction. Describe what could be done to each object to bring about a physical
change (change in its physical properties only) and a chemical change (change in its
chemical and physical properties).
Table: Physical and Chemical Interactions
Object
Description of
a Physical Change
5
Description of
a Chemical Change
Activity 8 Practice
1. (a) I think the pellets are metallic,
because they have three of the
same physical properties of
metals –they are shiny and good
conductors of both electric
current and heat energy.
(b) I think the pellets are a
metallic alloy (mixture of two
metals). Since two different
substances separated out during a
heat-conduction or infrared
interaction that resulted in a
phase change (a physical
interaction), it must be an alloy
and not an element (a single
substance).
2. (see chart below)
raw egg
antacid tablet
pencil
mini-bike
Unit 5 • Chapter 2
Object
Raw egg
© It’s About Time
Antacid tablet
Pencil
Description of
a Physical Change
489
Description of
a Chemical Change
Cracking the egg’s shell
Frying the egg in a skillet
Beating the egg in a bowl
Boiling the egg
Breaking the tablet into small pieces
Digesting the tablet
Crushing the tablet
Adding it ot water so it makes a gas
Sharpening the pencil point
Burning the pencil
Breaking the pencil in half
Minibike
Dissolving the dirt off the
minibike by rinsing with water
Burning gasoline by running the
minibike’s engine
Bending a fender
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Activity 9 Practice
1. Periodic Table (C) shows the
location of the highly reactive
metals.
Activity 9: Groups and the Periodic Table
(Questions 1-5) Refer to the six diagrams of the Periodic Table shown below.
2. Periodic Table (D) shows the
location of the noble gases.
3. Periodic Table (B) shows the
location of the highly reactive
nonmetals.
(a)
(b)
(d)
(e)
(c)
4. Periodic Table (F) shows the
location of the transition metals.
5. Periodic Table (A) shows the
location of the rare-earth metals.
(f)
6. (c)
1. Which Periodic Table (a, b, c, d, e, or f) shows the location of the highly reactive
metals?
7. (a)
2. Which Periodic Table shows the location of the noble gases?
3. Which Periodic Table shows the location of the highly reactive nonmetals?
8. (c)
4. Which Periodic Table shows the location of the transition metals?
5. Which Periodic Table shows the location of the rare-earth metals?
6. The elements in each column (group) of the Periodic Table of Elements
a) have the same densities at room temperature.
b) have the same melting and boiling temperature.
c) have very similar chemical properties.
d) are all metals, nonmetals or metalloids.
e) are all gases, liquids, or solids at room temperature.
7. A common chemical property of the alkali and alkaline earth metals is that they
a) react with water to make bases.
b) have high melting temperatures.
c) react with water to make acids.
d) are soft metals that you can cut with a knife.
e) do not react readily.
8. A common chemical property of halogen elements is that they
a) react with water to make bases.
b) have high melting temperatures.
c) react with water to make acids.
d) are all gases at room temperature
e) do not react readily.
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SCIENTISTS’ CONSENSUS IDEAS—ANSWERS
Scientists’ Consensus Ideas
Unit 5 Chapter 2 Answer Keys
Idea 1. Physical Interactions and
Physical Properties
A. A physical interaction is any type of interaction (such as mechanical, heat conduction, infrared, or electric
current) that does not result in any new materials. (Activity 2)
B. The evidence of a physical interaction is a change in the physical properties of an object (such as its
temperature, density, hardness, flexibility, electrical conductivity, phase, size, or shape), but no change in
the chemical properties of the object. That is, the kind of materials the objects is made of stays the same.
(Activity 2)
Examples of physical interactions that change the temperature of an object:
• sawing a log (friction)
• ironing clothes (heat conduction)
• warming hands near a cup of hot chocolate (infrared)
• heating soup on a stove (heat conduction and infrared)
Examples of physical interactions that change the size and/or shape of an object:
tearing, shredding, stretching, grinding, tying, separating, pull apart, unraveling, untying, squeezing,
compressing, breaking, cutting
Examples of physical interactions that change the phase of a substance:
• boiling water on the stove
• freezing water in the freezer
• dew appearing on grass
• melting solder (metal alloy)
• lava from volcano cooling to solid
• evaporation of a puddleby cooling air to –218ºC
• meteorite hitting ocean heats water so boils
C. A reversible interaction is any interaction where the original substances can be recovered with another
physical interaction (such as a heat conduction interaction that results in a phase change). Dissolving of one
substance into another, such as a solid in a liquid, is a physical interaction when it is reversible. (Activity 2)
Example of Dissolving That is a Physical Interaction (Reversible)
• dissolving salt in water
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• dissolving sugar in tea
Example of Dissolving That is A Chemical Interaction (Not Reversible)
• dissolving effervescent antacid tablet in water
• dissolving baking soda in vinegar
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Idea 2. Classifying Materials as Mixtures or
Single Substances
Chemists use properties that tell us something about the make up or composition of materials to
classify materials. Chemists first classify materials as mixtures or single substances. (Activity 4)
A. Mixtures. You can combine different masses of two or more materials together to make a mixture. All
mixtures can be separated into their component substances by physical interactions.
1. Mixtures with pieces of substances ranging from large to microscopic can be separated into their
component substances by settling and mechanical devices like tweezers, knifes, strainers, filter paper,
or a centrifuge.
2. Solutions (mixtures where one substance is dissolved in another substance) can be separated into
their component substances by heat conduction or infrared interactions that result in a phase change.
Examples of Mixtures:
brass, hot sauce, milk, muddy water, blood, salt water
A. Single Substances. Single substances cannot be separated into different substances during any kind of
physical interaction. No pieces of the substances in a solution can be seen, even through the best visiblelight microscopes.
Three Examples of Single Substances:
copper, sugar, sulfur
Idea 3. Classifying Single Substances and Elements
or Compounds.
A. Compound. A compound is a single substance that can be broken down into simpler substances during
chemical reactions. (Activity 5)
Examples of Some compounds:
salt (sodium and chlorine), calcium carbonate (calcium, carbon, and oxygen), calcium oxide (calcium and
oxygen), carbon dioxide (carbon and oxygen), water (hydrogen and oxygen), acetic acid (carbon, hydrogen,
and oxygen), sugar (carbon, hydrogen, and oxygen)
B. Element. An element a single substance that does not break down into simpler substances during
chemical reactions. (Activity 5)
1. Elements are the “basic ingredients” out of which everything is made. (Activity 5)
2. Over 100 different elements have been identified. 92 elements are found in nature, and the others are
made in the laboratory. (Activity 5)
nature (by themselves). (Activity 5)
Examples of elements found by themselves (not in compounds):
carbon, nitrogen, oxygen, sulfur, helium, neon, argon, krypton, xenon, and radon
4. Some elements are abundant — there is a lot of the element in the Earth’s crust.
(Practice for Activity 6).
Examples of abundant elements:
oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium
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SCIENTISTS’ CONSENSUS IDEAS—ANSWERS
5. Some elements are scarce–only tiny amounts are found in the Earth’s crust. (Activity 5)
Examples of scarce elements:
Answers will vary–any unfamiliar metal or non-metal, usually with strange names (e.g., yttrium, osmium,
rhenium, gadolinium, and so on).
Idea 4. The Periodic Table of the Elements
Families of elements with similar properties are grouped together on the Periodic Table of the
Elements.
A. Each element has a one, two, or three letter chemical symbol that allows chemists all over the world to
communicate. Chemical symbols are usually the first letter(s) of the Latin name of the elements. Scientists
who discovered some of the elements named them after places (e.g., californium) or famous scientists
(e.g., curium, einsteinium, and seaborgium). (Activity 6)
B. Elements with metallic physical properties .are located to the left of the zig-zag line.
Examples of metallic physical properties (Activity
5):
solid at room temperature (except mercury); usually silver or
gray color; shine brightly when polished; tend to have medium
to high melting temperatures and densities; malleable (can be
shaped by pounding or hammering); good conductors of heat
energy and electric current
C. Elements with nonmetallic physical properties are located
to the right of the zig-zag line (Activity 6)
Examples of nonmetallic physical properties
(Activity 5):
Nonmetals exist in all three phases – gases, liquids, and solids – at room temperature; have different colors
and solids are dull; tend to have low melting temperatures and densities; solids are usually brittle (not
malleable); and nonmetals are poor conductors of heat and electrical current.
D. The nonmetal elements on the far right of the periodic table (Column 18) are called the noble gases. The
noble gases are stable or chemically un-reactive. For this reason, they are all found in the Earth’s
atmosphere. (Activity 6)
Examples of nonmetal, noble gases (both name and chemical symbol):
helium (He), neon (Ne), argon (Ar), Krypton (Kr), xenon (Xe), Radon (Rn).
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E. The elements that border the zig-zag line, such as silicon, are called metalloids or semi-metals. Metalloids
have properties of both typical metals and non-metals. There are only a few metalloid elements, but they
are important because of their unique semiconductor electrical property. This is an essential property for
computer chips. (Activity 6)
Examples of metalloids (names and chemical symbols):
boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), astatine (At)
F. Elements next to each other, in a row or column, have the most similar properties. (Activity 6)
Example of the similar properties of the three naturally-occurring elements in Group 11:
The coinage metals, copper (Cu), silver (Ag), and gold (Au), have similar properties of high electrical
conductivity, ductility (can be stretched into thin wires), and resistance to corrosion (surfaces do not react
chemically with other substances in environment).
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Unit 5 Chapter 2 Activity 9
(Learning About Other Ideas)
Scientists’ Consensus Ideas:
Idea 5. Groups and the Periodic Table
The elements in each column (group) have similar chemical (and some physical) properties. As
you move across each row of the periodic table, the chemical properties repeat in a regular
(periodic) pattern.
A. The metals in Group 1 (alkali metals) and Group 2 (alkaline earth metals) are highly chemically reactive
with other substances. They are so reactive they are never found in nature.
1. They react with water to make bases.
2. Many react with the oxygen in air, so they need to be stored in oil.
3. The alkali metals are slightly more reactive than the alkaline earth metals.
Names (with symbols) of Group 1 (alkali) metals:
lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr)
Names (with symbols) of Group 2 (alkaline earth) metals:
beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and Radium (Ra)
B. The transition metals (Groups 3–12) are much less reactive than the alkali and alkaline earth metals. More
can be found in their native (elemental form), like copper, gold and silver. Although less reactive, they do
combine with other elements.
Examples (name and symbol) of some common transition metals:
Answers will vary. Common transition metals include aluminum (Al), iron (Fe), nickel (Ni),
copper (Cu), zinc (Zn), silver (Ag), tin (Sn), gold (Au), lead (Pb). Other transition metals
include titanium (Ti), chromium (Cr), cobalt (Co), tungsten (W), platinum (Pt), and
mercury (Hg).
C. The Group 17 (halogen) nonmetals are highly chemically reactive with other substances. They are so
reactive they are not found in nature (by themselves).
1. They react with water to make acids.
2. Many react with metals to form compounds called salts (halides).
Names (with symbols) of Group 17 (halogen) nonmetals:
fluorine (Fl), chlorine (Cl), bromine (Br), iodine (I), and astatine (At)
D. The Group 18 nonmetals are called the noble gases. In nature, they are chemically stable or unreactive.
Names (with symbols) of Group 18 nonmetals (noble gases):
helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn)
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They are so chemically stable they are all found in nature.
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SCIENTISTS’ CONSENSUS IDEAS—ANSWERS
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NOTES
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