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Matter, Atoms, Molecules, and Elements

by Cindy Grigg

1

Answer the following questions BEFORE you read this book. It is okay if you do not know as much as you thought. Do the best you can!

1.What are the things around you made of?

2.How does water change into ice or water vapor?

3.What do you know about atoms?

2 Matter, Atoms, Molecules, and Elements

Look at this picture. What do you see? Students, a book, a pencil, a window. What are these things made of?

Books are made of paper, glue, and ink. The pencil is made of wood, graphite, metal, and an eraser. Windows are made of glass. Students are made of living cells, tissues, and organs.

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Each of the objects in the first picture is very different from the others. Yet all the objects are alike in some ways. All these things are matter.

Matter is anything that takes up space and has mass. Matter is the "stuff" that everything in the universe is made of. Mass is the amount of matter, or stuff, that something is made of.

4 Matter, Atoms, Molecules, and Elements

This clump of matter in space is forming new stars.

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These things all take up space. The amount of space they take up - their volume - can be measured. Their mass can be measured, too. This spring scale is one tool that can be used to find the mass of an object.

6 Matter, Atoms, Molecules, and Elements

Volumes of cubes can be found by multiplying the measurement of their length, width, and height.

In the kitchen, we use a measuring cup to find the volume of liquids. This measuring cup shows volume in three different units: cups, fluid ounces, and milliliters.

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All matter is made of atoms. Atoms are the smallest pieces of an element that still have the properties of that element.

For instance, you can take a piece of aluminum and cut it into tiny little pieces, and each piece is still a shiny, lightweight metal. If you could cut that aluminum into pieces that are too small to see with your eyes or even with a good microscope, it would still be aluminum.

8 Matter, Atoms, Molecules, and Elements

Elements are made of only one kind of atom. Elements are called "pure" substances.

There are only about 120 different elements. The periodic table is a visual display showing the elements. Aluminum is AL. Its atomic number is 13.

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Atoms of different elements can combine to make many other things. When two or more atoms combine, they make a molecule. A molecule is the smallest amount of a substance that can exist.

A molecule can be made of the same kind of atoms or different kinds. A molecule of ozone is made of three oxygen atoms joined together. A molecule of water (H2O) is made of one oxygen atom bonded to two atoms of hydrogen.

10 Matter, Atoms, Molecules, and Elements

Just as the 26 letters of our alphabet can combine to make millions of words, the elements can combine to make a huge number of different kinds of substances.

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How do atoms join together? You may already know that atoms are made up of even smaller bits of matter. The nucleus (or center) of the atom holds the protons and neutrons. Circling outside the nucleus are the electrons.

Note: This is a simplfied picture of how an atom might look.

12 Matter, Atoms, Molecules, and Elements

One way that atoms combine is to share electrons. This is called covalent or chemical bonding. When atoms join together and form chemical bonds, or when chemical bonds are broken between atoms, we call that a chemical reaction.

Oxygen has six electrons in its outer shell. It needs two more electrons to fill its outer shell. Hydrogen has one electron. It needs one more. When two hydrogen atoms share their electrons with one oxygen atom, all three atoms are happy!

(Note: The oxygen atom should be larger than the two hydrogen atoms.)

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Physical changes in matter don't form or break any chemical bonds. Water goes through a physical change when it freezes into ice or disappears into water vapor.

What happens to the water in a mud puddle after the sun comes out?

14 Matter, Atoms, Molecules, and Elements

Physical changes are changes in the physical properties of a substance. They can be changes in color, shape, or size. Physical changes don't create new substances.

Adding or taking away heat causes physical changes in water. Ice changes into liquid water when it is heated, either on a stove top or by the sun. With even more heat, liquid water changes into water vapor. The water in a mud puddle evaporates. It changes from a liquid to a gas. It becomes water vapor in the air.

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Matter commonly exists on Earth in three phases or states: solid, liquid, and gas.

Changes in states of matter are physical changes. Physical changes can usually be undone. If ice melts, we can undo that physical change by simply freezing the water again.

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Solid butter melting on warm corn on the cob is a physical change. Melted butter can become solid again by cooling it.

Butter, water, molecules, and even elements can change from one state to another without changing their atoms. Iron, an element that is usually a solid, can be heated and melted into a liquid. It is made of only iron atoms in both the solid and liquid states.

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Water is H2O -- made of one oxygen atom bonded to two atoms of hydrogen- whether it is solid ice, liquid water, or gaseous water vapor in the air. It can easily change from one state of matter to another, but its chemical state remains the same.

18 Matter, Atoms, Molecules, and Elements

Lucky for us, matter can change states. It wouldn't be much fun if water was always in its solid state, would it? Imagine breathing air that had chunks of ice instead of water vapor in it! Imagine chunks of ice falling from the sky instead of rain. Imagine oceans and swimming pools filled with ice instead of water. Lucky for us, all matter is not alike.

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On Earth, most matter exists in three different states - solid, liquid, and gas. The stars are made of plasma, a fourth state of matter. Matter has mass and volume, and these can be measured. Look around you. Everything you see is made of matter - even the stars in the sky at night. Matter is made of atoms. Atoms of only 120 different elements can combine to make many substances.

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Glossary

atoms - the smallest pieces of elements

covalent or chemical bonding when two or more atoms combine by sharing electrons

electron- a particle of an atom that circles outside the nucleus

elements - pure substances made up of only one type of atom

mass - the amount of matter something contains

matter - anything that takes up space and has mass; matter makes up everything in the universe

molecule - the smallest amount of a substance that can exist; made of two or more atoms

nucleus - the center of an atom, containing the proton(s) and neutron(s)

neutron - a particle of an atom, found in the nucleus

proton- a particle of an atom, found in the nucleus

physical changes changes in the physical properties of a substance, such as size, color, shape, or state of matter

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Answer the following questions AFTER you have completed this book.

1.What three states of matter are commonly found on Earth?

2.How many atoms make up one molecule of water? Name them.

3.What state of matter are stars?

4.Circle the parts of an atom.election electron oxygen neutron

proton nucleus matter mass

5.A chemical reaction happens when two or more atoms

chemical bonds.

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6.Compare an atom to a molecule. How are they alike? How are they different?

23Matter, Atoms, Molecules, and Elements

7.Describe the periodic table. What information can you find on it?