Elements & Compounds oh my

Get ready to learn about elements and compounds. 

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What is matter?

Matter is everything that you can see, touch, taste, and feel. Anything that has mass and takes up space is matter. Mass measures how much matter is in an object, and volume measures how much space the matter occupies. What are some examples of matter in the classroom?


Matter can be made from only one kind of material, or it can be a mixture of different kinds of materials. Think about the examples of matter that the class identified. Which examples are only one kind of matter? Which examples are mixtures of different types matter?

When matter is made of different types of materials, it is called a mixture. When matter is made of only one kind of material, it is a pure substance. A pure substance is matter that is uniform throughout and has consistent properties.

All matter is made up of very small particles called atoms. Atoms are the building blocks of all matter. When a substance contains only one type of atom, it is called an element. Each element has a special name and unique properties that are different from all the rest of the elements. All known elements are organized on a chart called the periodic table of elements. An element is a pure substance and is made of only one type of atom; it cannot be broken down into a simpler substance.

Take a look at the Periodic Table of Elements provided by your teacher. You will see many boxes that contain information for each of the elements. The first box is for the element hydrogen.

The name of this element is hydrogen. The name of an element can be found at the bottom of the box. Every element is also represented by a chemical symbol, a one or two-letter symbol. When the element is represented by two letters, the first letter is always capitalized and the second letter is lower case. The chemical symbol of hydrogen is H.

Go To Google Classroom and access STEMscope Elements and Compounds Explain Student Journal

Answer questions 1 through 5

Pure Substance Definition

A pure substance is a sample of matter with both definite and constant composition with distinct chemical properties.

Alternate Spellings: chemical substance

Examples of Pure Substances

Examples of pure substances include elements and compounds. Alloys and other solutions may also be considered pure.

  • water
  • diamond
  • gold
  • table salt (sodium chloride)
  • ethanol
  • brass
  • bronze
  • saline solution



  1. A pure substance is matter that is made of only one kind of matter, is uniform throughout, and has consistent properties.








Examples of Things That Are NOT Pure

Basically, any heterogeneous mixture is not a pure substance. If you can see differences in the composition of a material, it's impure, at least as far as chemistry is concerned.

  • rocks
  • an orange
  • wheat
  • light bulb
  • a shoe
  • a sandwich

What is an Element?

An element is a substance consisting of atoms which all have the same number of protons - i.e. the same atomic number.

Elements are chemically the simplest substances and hence cannot be broken down using chemical methods. Elements can only be changed into other elements using nuclear methods.

Although an element's atoms must all have the same number of protons, they can have different numbers of neutrons and hence different masses. When atoms of the same element have different numbers of neutrons, they are called isotopes.


The Most Abundant Elements

With only one proton, hydrogen is the simplest, lightest element, followed by helium, which has two protons.

At 75 percent, hydrogen is also the most abundant element in the universe, followed again by helium at 23 percent, then oxygen at 1 percent. Each oxygen atom has eight protons. All of the other elements make up the remaining 1 percent.

In the earth's crust, oxygen (47 %) is the most abundant element, followed by silicon (28 %) and aluminum (8 %).


Element Names and Numbers

All of the elements have been named. Some of these names are familiar to us, such as nitrogen and sodium, and some are less familiar, such as dysprosium and roentgenium.

We can also name elements using their atomic numbers. For example, element 1 is hydrogen, element 2 is helium, element 3 is lithium, element 8 is oxygen, etc.

How Many Elements Are There?

There are currently 115 accepted elements and three elements whose existence has been claimed, but not yet accepted (elements 113, 115 and 118).

We use the periodic table to display all of the elements in an organized way.

Elements Ancient and Modern

Some elements have been known for thousands of years, and we do not know who discovered them. These are: antimony, arsenic, carbon, copper, iron, gold, lead, mercury, silver, sulfur, and tin.

All other elements have been discovered since 1669; it was in this year that Hennig Brand became the first named person to discover a new element - phosphorus.

Combining Elements

An element can combine with one or more other elements to form compounds, of which there are millions. For example, one of the best-known compounds is water, written chemically as H20, which means that water is made of two atoms of hydrogen combined with one of oxygen.

An element is a pure substance that is made of only one type of atom that cannot be broken down into a simpler substance.


The periodic table is a list of the known elements. The table lists an element’s name and chemical symbol.



One or two letter chemical symbols identify an element. Single letters are always capitalized. Two letters are used in cases that identify elements whose names begin with the same letter; the first letter is capitalized, and the second letter is lower case.

Go To Google Classroom and access STEMscope Elements and Compounds Explain Student Journal

Answer the next section.

Part II: Elements, Compounds, and Mixtures

Student Guide

When you were in elementary school, you learned about mixtures. Remember that the properties of the mixture depended on the parts of the mixture. For example, salt water is wet like water and salty like the salt. Saltwater keeps the properties of its ingredients because it is a mixture. Mixtures can be separated by simple mechanical methods like sorting, evaporation, filtering, or magnetic attraction.

Matter that is a pure substance is very different from mixtures. Pure substances are made from only one type of matter and cannot be separated by physical methods. Pure substances can be divided into two categories, elements, and compounds. You already know that elements are pure substances that cannot be broken down into simpler substances. When elements combine, they form new substances called compounds. Compounds have entirely new properties, different from the properties of the elements that it contains. Compounds are pure substances made of two or more kinds of atoms bound together. Compounds can also be broken down into simpler substances.


Part III: Elements Make Compounds

Student Guide

Perhaps you sometimes refer to water using its chemical name: H 2 o or H20. H2O is the chemical name of water that identifies the building blocks of water. What element has the chemical symbol H? What element has the chemical symbol O? The compound water is made of the elements hydrogen and oxygen. Hydrogen and oxygen each have their own distinctive properties such as: freezing and boiling temperatures, color, and mass. The properties of water are very different from the properties of hydrogen and oxygen.

Carbon dioxide is another compound that is familiar to you because it is the gas that you exhale with each breath. You may have heard carbon dioxide referred to as C-O-2 or CO2. The O in CO2 is the same oxygen element that you find in the water. You may already know the name of the element that C stands for, but if you did not know the name, you could look it up in the Periodic Table of Elements. What does the C in CO2 represent? The small number 2 in CO2 represents the number of atoms of oxygen that are in carbon dioxide, two oxygen atoms. The C in the CO2 is not followed by a small number, so that means there is only one atom of carbon in carbon dioxide. This small number is called a subscript.

Your teacher will provide you with cubes in four different colors, four index cards (two labeled compound and two labeled element) and a beaker. The cubes represent atoms of the elements carbon, oxygen, hydrogen and copper.

20 blue = 20 oxygen;

4 red = 4 carbon;

8 yellow = 8 hydrogen;

4 green = 4 copper

  1. First make oxygen gas, or O2, by connecting two blue cubes. Is Oan element or compound? Recall that an element is a pure substance made of only one kind of atom, so O2 is an element. Use the blocks to make three more individual models of O2 and set these models aside to use later.

Next use the blocks to make a model of carbon dioxide, or CO2. Is carbon dioxide an element or a compound? Carbon dioxide is a pure substance made from two different elements so it is a compound. Use the blocks to make three more individual models of carbon dioxide, CO2, and set these models aside to use later.

  1. Now use the blocks to make a model of the compound water, H2O. How do you know by just looking at this model that it is a compound? Compare the single model of water to the models of oxygen that you made earlier. These models clearly represent when a substance is an element or a compound simply by looking at their colors. Make three more models of water.
  1. Leave the individual atom models of the element copper in a pile. Identify the models that you created as elements or compounds by placing a labeled index card next to the appropriate set. Complete the chart in Part III of your Explore Student Journal.
  1. All four sets of models that you made are pure substances! Recall that a pure substance is uniform throughout and has consistent properties such as melting or freezing points, hardness, and whether or not the substance burns (flammability).
  1. Use any combination of the pure substances that you modeled to create a mixture by placing them in a beaker. Your mixture will probably not look like the mixtures created by other groups. Recall that mixtures can vary in the amounts and types of matter present, which explains why mixtures do not have consistent properties.

Complete Part III in your Explore Student Journal.

Complete the Google Classroom assignment and the Student Handout from Monday.