Name ______________________________________ Period _______ Date ___________
Directions: Read and find answers to questions. Answer on separate paper. Underline the answers in the text.
1
What is matter? Matter is the stuff that makes up everything in the universe. Matter has mass and takes up space. Matter is made of atoms. Solids, liquids, gases, and plasma are all matter. When all atoms that make up a substance are the same, then that substance is an element. Elements are made of only one kind of atom. Because of this, elements are called "pure" substances. An atom is the smallest piece of an element that still has the properties of that element. For example, aluminum is a lightweight, shiny metal. If we took a piece of aluminum and cut it into small pieces, it would still be aluminum. It would still be a lightweight, shiny metal.
The smallest piece would be called an atom. Atoms are so small they cannot be seen even with a microscope. Atoms consist of a nucleus that has protons and neutrons surrounded by electrons outside the nucleus.
2
Atoms of different elements can combine to make new substances. A molecule is formed when two or more atoms join together chemically. If atoms combine that are of two or more different elements, we call that a compound. All compounds are molecules, but not all molecules are compounds. When two hydrogen atoms combine with one oxygen atom, it becomes the compound water. The oxygen we breathe is actually two atoms of oxygen combined, so it is a molecule of oxygen. We use abbreviations for elements, molecules, and compounds. These abbreviations are called chemical symbols. The chemical symbol for an oxygen molecule is O
2
.
3
The compound water has a chemical symbol of H
2
O. This is like the "recipe" for water.
It tells us that a water molecule is made of two atoms of hydrogen and one atom of oxygen.
Oxygen is a gas that we can't see, hear, smell, taste, or feel. But it's in the air we breathe, and without it we would die. Hydrogen, also a gas, is the lightest substance on Earth. When two atoms of hydrogen join together with one atom of oxygen, those two gases make a liquid compound we call water. Water, a liquid at room temperature, is a very different substance from the two gases that it is made of. Many different compounds can be made when different atoms combine.
4
There are 93 elements that naturally occur on Earth. Many more have been made by scientists in a laboratory. With that many elements to form combinations, many millions of different molecules and compounds can be made. How is that possible? Think of our alphabet. The English alphabet has 26 letters. Those 26 letters can be combined in different ways to make millions of words. Atoms are like the letters of the alphabet and the compounds they make are like words.
5
Now that you have learned the language of chemistry, you are ready to learn more about elements, atoms, and the ways they combine.
1.
What is matter?
2.
What is an element?
3.
What is an atom?
4.
What are the parts of an atom?
5.
Abbreviations for elements, compounds, molecules are called
_________________________________.
6.
How many elements occur naturally on Earth?
7.
What is the lightest substance on Earth?

Name ______________________________________ Period _______ Date ___________
Directions: Read and find answers to questions. Answer on separate paper. Underline the answers in the text.
1
All matter is made up of tiny particles called atoms. When different kinds of atoms join together, they form molecules called chemical compounds. In compounds, atoms of different elements are linked together.
2
Each group of linked atoms is called a molecule. Compounds may be made of many molecules. Compounds often have physical properties that are very different from the properties of the elements they are made of. For instance, oxygen in the air is in the form of a gas. Hydrogen is also a gas. When oxygen atoms join with hydrogen atoms, they form molecules of liquid water. What would happen if the atoms of elements couldn't join together to form molecules? There would be no such thing as water. The world would be very different if compounds didn't exist.
3
A compound that you probably see every day is sodium chloride or table salt. It is formed when sodium atoms join with chlorine atoms. Sodium is a gray metal, and chlorine is a yellowish poisonous gas. How can these two different substances form a white solid that we can eat?
4
When sodium and chlorine combine to form salt, they undergo a chemical reaction. In a chemical reaction, atoms or molecules join, break apart, or switch places. In all chemical reactions, the beginning substance or substances undergo change and form new substances with different properties. The beginning substances are called reactants. The final substances are called products.
5
Each molecule of sodium chloride is made up of one atom of sodium and one atom of chlorine. But other compounds may have more of one kind of atom than of another kind of atom. For example, water is made up of one oxygen atom and two hydrogen atoms. Its chemical symbol is H2O. This is like the "recipe" for water. You must have two hydrogen atoms for every oxygen atom to make water.
6
There are about ninety naturally occurring elements on Earth. If atoms could not join to form compounds, the world would be a very different place! Everything would be in the form of one of the elements on the periodic table. Plants and photosynthesis wouldn't exist because each involves compounds. We wouldn't have any gasoline or cars because both are made of compounds. There would be no oceans, lakes, or rivers because water is a compound. We wouldn't be able to make plastics anymore because plastics are compounds. Without compounds, life as we know it on Earth could not exist.
1.
What is all matter made of?
2.
When different kinds of atoms join together they make
____________________________________________.
3.
What is a molecule?
4.
How many different molecules are found with one compound?
5.
Do compounds always have the same physical properties as the elements they are made of?
6.
What is the name of the beginning substances in a chemical reaction?
7.
What is the name of the final substances in a chemical reaction?
8.
What is the chemical compound for table salt?

1 Atoms
2 Molecules called chemical compounds
3 A group of different kinds of atoms linked together
4 True
5 False
6 Reactants
7 Products
8 One atom of sodium and one atom of chlorine e properties of that element
4 A nucleus that has protons and neutrons with electrons outside
5 Chemical symbols
6 H
2
O
7 93
8 Hydrogen