5 1 understanding matter (physical sciences)

Physical Sciences
Standards
Preview
1.e. Students know scientists have
developed instruments that can
create discrete images of atoms and
molecules that show that the atoms
and molecules often occur in wellordered arrays.

Standard Set 1. Physical Sciences
1. Elements and their combinations
account for all the varied types of
matter in the world. As a basis for
understanding this concept:
1.b. Students know all matter is made
of atoms, which may combine to form
molecules.

1.f. Students know differences in
chemical and physical properties
of substances are used to separate
mixtures and identify compounds.

1.c. Students know metals have
properties in common, such as high
electrical and thermal conductivity.
Some metals, such as aluminum (Al),
iron (Fe), nickel (Ni), copper (Cu),
silver (Ag), and gold (Au), are pure
elements; others, such as steel and
brass, are composed of a combination

of elemental metals.

1.h. Students know living organisms
and most materials are composed of
just a few elements.
1.i. Students know the common
properties of salts, such as sodium
chloride (NaCl).

1.d. Students know that each element
is made of one kind of atom and
that the elements are organized in
the periodic table by their chemical
properties.

Genre

Nonfiction

Comprehension Skill

Make Inferences

Text Features

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Glossary

Science Content

Matter

Scott Foresman Science 5.1

ISBN 0-328-23564-4

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by Johanna Biviano


Vocabulary
atom
atomic number
chemical property
compound
element
molecule
physical property
solution

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1 2 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06

by Johanna Biviano


Properties of Matter

This balance is one tool that can
measure physical properties.

In the mid-1800s, the Gold Rush brought people from all
over the world to California. Miners were looking for nuggets
of gold like the one below. The gold they were hoping to find
is a basic kind of matter called an element. Elements are the
building blocks of matter. They cannot be broken down into
smaller pieces.
Out of more than 100 elements, only a few exist in nature in
a pure form. Gold is one of them. In fact, most matter is made

up of groups of elements. Almost all of Earth’s crust is made
up of eight elements. They are oxygen, silicon, aluminum, iron,
calcium, sodium, potassium, and magnesium. Most living and
nonliving things are made up of a few elements that combine in
several ways.
Gold is an element.

Elements have distinct properties from one another. They
have physical properties that can be seen or measured without
changing the material. A physical property is often obvious to
one of your five senses. Color, odor, and hardness are physical
properties. There are different tools you can use to measure
physical properties. These include metersticks, balances, and
spring scales. Electron microscopes help scientists look at the
structure of elements. An element’s chemical properties have
more to do with how an element reacts with other elements.

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Physical Properties
You can tell a lot about an element’s physical properties
by looking at it and touching it. From the picture of silver, you
can see that it is gray and shiny. If you could touch it, it would
feel solid. The color and phase of matter (solid, liquid, gas) are
physical properties.
Silver also has mass and weight. You can measure silver
to find its mass. Finding the mass with a balance will tell you

how much matter is in an object. The weight of silver can be
determined with a spring scale. This piece of silver will always
have the same mass, but its weight can change. Weight is a
measure of how much gravity affects an object. Let’s say this
silver weighs six pounds at sea level. On the Moon, where there
is less gravity, it would only weigh one pound! Magnetism,
the temperatures at which a substance boils and freezes, and a
substance’s ability to dissolve are all physical properties.

Oxygen and water cause
iron to rust.

Chemical Properties

Silver is a pure element.

4

Using chemical properties is a useful way to identify
substances. Chemical properties can be seen when you combine
one substance with another.
Remember that iron turns to rust when it is combined with
water and oxygen. This is a chemical property of iron. Iron
is easy to bend and shape. This is a physical property called
malleability. Bending iron doesn’t create a chemical reaction, but
adding oxygen and water does. Another chemical property is
flammability. This is the ability of a substance to burn.

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Parts of Matter
An atom is the smallest particle of an element that has the
same properties of the element. The atoms in one element are
different from the atoms in another element. The structure of
atoms determines the chemical and physical properties of an
element. It also shows how an element can combine with other
elements.
Pure metals, such as silver, are made up of only one kind of
atom. This means they are made up of only one element. If you
could break silver into its smallest possible parts, you would have
one tiny atom of pure silver.
An atom has smaller parts that make up its structure. The
nucleus, or center of the atom, has a combination of protons and
neutrons. Protons have positive electric charges, and neutrons
have no charge. The number of protons in a nucleus is unique
to each element. The number of protons is an element’s atomic
number. An atom also has electrons. Each electron has a
negative charge, and atoms can lose or gain electrons without
changing the element. Some electrons can be shared with
other atoms.

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Scientists use powerful
microscopes to look at
parts of matter that are too
small to be seen with other
microscopes.

Many substances are
not pure. Instead they
are made up of several
atoms from one or more
elements. When atoms
combine, they form
molecules. A molecule is
the smallest possible part
of a substance made from
more than one atom. It
has the properties of that
substance.
A molecule can have atoms from one element or atoms
from several different elements. The air we breathe has different
molecules. The oxygen molecules in the air are groupings of two
atoms of the same element. Other gases in air, such as carbon
dioxide, have atoms of different elements.
Scientists today have come a long way in their
understanding of atoms and matter. They have developed
technologies that help them make images of atoms and
molecules. These images show that atoms and molecules are
often well-ordered in a grid-like pattern.

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The Periodic Table of Elements
The periodic table of elements is a tool for organizing the
known elements. The table starts with the smallest atomic
number in the first row and increases from left to right. Each

column in the table organizes elements by shared chemical
properties. You can predict the properties of an element if you
know which column it is in.
Each element has a short symbol with a capitalized first
letter. These symbols are used in chemical formulas. For
example, the H stands for hydrogen and Ca stands for calcium.

Periodic Table
of Elements

Each element has a unique number of protons and electrons.
They give each element its properties. Scientists sort elements
into three groups according to their properties: metals,
nonmetals, and metalloids.
Metals are often good conductors of electricity, are solid
at room temperature, and are ductile, meaning they can be
stretched without breaking. Nonmetals are identified by their
brittleness, their inability to conduct heat or electricity well, and
their tendency to break if stretched. The third group, metalloids,
includes elements that share properties of metals and nonmetals.

Metals
Metalloids (semimetals)
Nonmetals

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Using the Periodic Table
The periodic table is a useful tool for understanding
elements, and it is full of information about each one. You only
need to know how to read it. The block for titanium, shown
below, shows you the type of information you can find about
any element in the periodic table.
Rows show increasing atomic weight, while columns show
similar properties. The table comes together in a regular pattern,
so you can predict an element’s properties based on its location.

Close-Up: Titanium

Each column in the table is a group or a family. Each family
includes elements with similar characteristics. They react with
substances in similar ways.
Group 1 includes metal elements that react strongly with
water. Hydrogen is an exception; it is a gas. Its atomic structure
is similar to other elements in its family. But its chemical
properties are different.
Rows in the periodic table are periods. They are not
grouped by similar characteristics. The element farthest to the
left is very reactive. The elements become less active as you
move to the right.
If you look at the groups below, the color of the blocks
indicates that the metallic elements on the left are very reactive.
The nonmetals on the right are less active.

Atomic Number: 22
Symbol: Ti
The elements on the

far left of the periodic
table are very reactive.

Name: Titanium

The elements on
the far right of the
periodic table are the
least reactive.

Titanium is a strong metal that
is very light.

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Properties of Metals

Mixed Metals

You have read about metals and may already know some
important things about them. Have you ever noticed that most
metals are shiny and can bend without breaking? Reflectivity
and malleability are properties many metals share. All metals
are also solid at room temperature, except for mercury. At room
temperature, mercury is a liquid.
Metals also share conductive qualities. A good conductor is a
material that lets heat and electricity travel through it. Metals are

ductile so they can be made into wire. These properties make
metals very useful for wiring your home and electrical devices.
Many common metals are pure elements. Nickel, iron, and
copper are all pure elements.

Many metals are not pure
elements. When two or more metals
are mixed together, a metal alloy
results. Mixing metals together
gives the alloy new and different
properties. For instance, when
carbon and iron mix together, the
resulting steel alloy is much stronger
than iron alone. Brass, another
common mixture made from
copper and zinc, is less malleable
than copper and prettier than zinc.
Musical instruments made of metal,
such as trumpets, saxophones, and
tubas, are often made of brass.

Brass is an alloy of copper and zinc.
It has different properties than
copper and zinc.

nickel
iron

copper

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Compounds
When two or more elements combine, they form a
compound. The compound has different properties than
the elements within it. For example, water is made up of two
hydrogen atoms and one oxygen atom. Both hydrogen and
oxygen are gases that you can’t see, touch, or hold at room
temperature. When they combine to form the compound water,
you can pour it, boil it, and freeze it.
Remember the letter symbols from the periodic table?
Compounds have formulas that use these symbols. The formula
tells how many atoms of each element make up the compound.
The formula for water is H2O. H is the symbol for hydrogen,
and the 2 tells you how many hydrogen atoms are in the
compound. There are no numbers after the O for oxygen, so
there is only one atom of oxygen in the formula. Water always
has twice as many hydrogen atoms as oxygen atoms.
hydrogen

oxygen

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= oxygen

= hydrogen

Oxygen, hydrogen, and carbon combine
to make sugar.

= carbon

hydrogen

Hydrogen and oxygen can join with other elements to create
completely new compounds. Oxygen, hydrogen, and carbon join
to make sugar. This crystal has little in common with oxygen
and hydrogen gas, or the solid carbon found in coal.
Elements react differently depending on what they combine
with. Sodium combined with chlorine reacts to form table
salt. Sodium combined with water creates a violent reaction of
sodium hydroxide and hydrogen gas.
Compounds make up much more of the substances on
Earth than pure elements. A very common substance, water, is a
compound that makes up about 60 percent of your body.

15


Salt Compounds
Many compounds form by sharing electrons, but there are
other ways for compounds to form. Salts are compounds made
up of particles held together by oppositely charged atoms.
Particles with more electrons than protons are negatively
charged. Particles with more protons are positively charged.
Opposite charges attract and pull the particles together.
Most salts share two properties: they are made up of one

metal and one nonmetal element, and they can form crystals.
Brittle crystals develop when particles arrange themselves in a
regular pattern. Common table salt is just one of many types of
salt that have these properties.
sodium

Salts can form when chemicals called acids and bases
combine. Hydrochloric acid is a highly dangerous acid. When it
combines with sodium hydroxide, a dangerous base, they form
sodium chloride and water. The salt is dissolved in the water, but
salt crystals form if the water evaporates. When hydrochloric
acid or sodium hydroxide is mixed with metals, the result is a
violent reaction.
Acids and bases can be poisonous
and corrosive. They can burn your
skin. It’s important to be very careful
while handling chemicals. Never
put any chemicals near your face
or in your mouth during science
experiments. Even though sodium
chloride is a harmless salt, many
salts are actually poisonous.

chlorine

Each crystal of salt has
an organized pattern.

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Sodium hydroxide (left) and
hydrochloric acid (right) react in
violent ways (when combined
with magnesium and zinc
pieces, respectively).

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What can salts do?
Salts, as you already know, are made up of metal and
nonmetal elements. They form into a regular pattern of brittle
crystals. They are also resistant to melting until they are heated
at a very high temperature. Even though salt is resistant to heat,
it dissolves very easily in plain water. If you continue to pour
salt into water, it will reach a point where it stops dissolving.
When salts dissolve in water, they make the water an excellent
conductor for electricity.

Salts dissolve in water.
At some point, the salt
will no longer dissolve no
matter how much you stir.

Once elements combine
to form salts, the salt has very
different properties than the
elements that went into it. The
photos below show how copper
combines with other substances to

form salts. When copper is combined
with sulfur and oxygen, copper forms a
blue salt. When combined with chlorine,
it forms a green salt. Neither of these salts
looks like copper, nor can they be made into wire or bent into
different shapes. They are now brittle crystals.
On its own, sodium is a soft metal that reacts explosively
with water. When combined with the poisonous yellow gas
chlorine, the two create the safe little crystals you recognize as
table salt.

pure copper

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copper +
sulfur + oxygen

copper +
chlorine

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Separating Mixtures
Not all elements bond together to form compounds.
A mixture is different from a compound. You know that
compounds can have different properties than the elements that
form them. In a mixture, the different elements do not bond
together. They keep their own properties. Think of it this way:

if you make a mixture of raisins with your cereal, the cereal does
not change color or flavor, and the raisins don’t change color or
flavor. They keep their individual properties.
In a mixture such as cereal and
raisins, the substances keep their
own properties.

Think of a mixture of sand and water. How would you
separate the two? The sand does not dissolve in water, so you
might try pouring the mixture through a coffee filter. The bigger
sand particles won’t be able to squeeze through the filter. The
water particles will drip right through.
In order to separate mixtures, it helps to know some of the
properties of the mixed substances. Knowing that sand has
bigger particles than water helps you decide to use a filter.
What about sand mixed with iron filings? Both particles are
about the same size, but do they have other properties? Iron is a
metal, and it is attracted to magnets. The rest of the sand is not.
A good way to separate iron from the rest of the sand would be
to use a magnet.

Magnetism is a physical
property of iron. This
allows it to be separated
from the sand with a
magnet.

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Solutions

Chromatography

When you pour sand into water, the sand particles sink to
the bottom. Other substances dissolve when mixed together,
such as salt in water. Instead of sinking to the bottom, the salt
spreads out evenly in the water. When a mixture has particles
spread out evenly like this, it is called a solution.
A solute is a substance that dissolves in a solution. Think
about salt and water. Salt is the solute. Water is the solvent, or
substance in which the solute dissolves. Water is an excellent
solvent for many different solutes.
Solubility is another physical property. Solubility describes
how much of a substance will dissolve in a solvent at a certain
temperature. You can still separate these mixtures, but you may
have to heat or cool the solution to remove the solute.

When you see a glass of green liquid, you can be pretty sure
it’s not a glass of water. There is probably a solute in it. How
can you know for sure? The process of chromatography uses a
substance’s solubility to separate it from other substances. Police
departments use this process to identify different substances.
Paper chromatography works like this: the experimenter
puts a dot of the substance on a strip of paper. One end of
the paper is placed in water or isopropyl alcohol. This solvent
moves up through the paper. When it reaches the solute, the
solvent pulls the colored parts, called pigments, up the paper. If a

pigment is very soluble, it will travel high up the paper.
When the paper dries, you have information about that
substance. If there are two
or more obvious colors on
the paper, your substance
was not a pure element.

This is a dilute solution. More solute
could dissolve in this solution.

This is a concentrated solution. It has
much more solute compared with the
amount of solvent.

Chromatography can
be used to identify
different substances,
such as pigments.

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Glossary

What did you learn?
1. What are some physical properties of elements?

atom

the smallest particle of an element with
the same properties of the element

atomic number

the number of protons in the nucleus
of an atom; the single most important
property of an element

chemical property

any property of a material that describes
how it changes into other materials

compound

a kind of matter made of a chemical
combination of two or more elements

element

one of more than 100 basic kinds of
matter that cannot be broken into smaller
pieces through physical or chemical
processes

molecule

the smallest part of a substance made

from more than one atom that still has
the properties of that substance

physical property

any property of a material that can be
seen or measured without changing the
material

solution

a mixture in which substances are spread
out evenly and will not settle

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2. What is the relationship between an element and an atom?
3. How is a molecule different from a compound?
4.

Choose an element from the periodic table
on pages 8 and 9. What do you want to know about it? Write four
questions you would like to have answered. Using the information
on your element’s block, try to answer your questions. Write a
paragraph about your element using the facts and details you
have discovered. Explain how you found the information as you
write.

5.

Make Inferences Pick three objects in your classroom. Just
from looking, touching, and smelling, what can you infer about
them? Where do you think they would belong on the periodic
table if they were pure elements? What led you to make your
inferences?