Your phone, the air you breathe, the ocean, and even you are all built from the same tiny pieces. What are they, and how do a few kinds of piece make everything?
By the end of this lesson, you will be able to:
Click a card to reveal what each word means. Click it again to close. You'll meet every one of these in the lesson below.
Imagine you tear a sheet of gold foil in half. Then in half again. And again, thousands of times, with a perfect tiny blade. Could you keep going forever, or is there a smallest possible piece?
Before we shrink down to the smallest piece, let's name the stuff we are shrinking into. Almost everything you can point to is matter, and it all passes two tests.
Matter is anything that has mass and takes up space (volume). All matter is made of tiny pieces called particles that are far too small to see. The tiniest particle is called an atom.
Matter is all around you, in every state:
Let's actually take that gold coin from the mystery and zoom in, step by step, until we reach the smallest possible piece. Use the button to keep zooming.
An atom is the smallest piece of matter that still behaves like that substance. One atom of gold is still gold. But if you could split that atom apart, the pieces would no longer be gold at all. For example, the smallest piece of gold that is still gold is a single gold atom.
There are many different types of atoms. Each type is defined by a name and a symbol (one or two letters). The periodic table is the chart that organizes every known type. The bigger number on each tile is its mass.
Tap any atom to see its name, symbol, and mass.
Every tile you just tapped is an element. The idea is simple but powerful.
An element is a substance made up of only one type of atom. A gold bar is pure gold, so it is the element gold: nothing but gold atoms, all the way through. For example, a chunk of pure gold is the element gold.
Atoms can join together and act as a single unit. The oxygen you breathe is not lonely single atoms; it travels as pairs.
A molecule is two or more atoms joined together that act as one unit. The air you breathe is full of oxygen molecules: two oxygen atoms bonded together, written O₂.
Remember the mystery? Hydrogen plus oxygen makes water, something completely different from either gas. That is the power of a compound.
A compound is a molecule that has two or more different types of atoms bonded together. Water is two hydrogen atoms bonded to one oxygen atom, written H₂O.
Add atoms to the tray and watch the model decide what you made. Then try to build the three target substances at the bottom. The builder names your creation and tells you whether it is an element or a compound.
Here are seven real substances. For each one, decide: is it an element (one type of atom) or a compound (different types bonded)? Tap your choice.
You started by asking what the smallest piece of matter is. Now you can answer that and explain how a few kinds of piece build the whole world.
Everything from this lesson in one place: the words to know and the goals you worked toward.
| Term | Student-Friendly Definition |
|---|---|
| Matter | Anything that has mass and takes up space (volume). |
| Atom | The smallest piece of matter that still behaves like that substance. The basic building block. |
| Element | A substance made of only one type of atom, such as gold or oxygen. |
| Periodic table | The chart that organizes every known type of atom, each with its own name and symbol. |
| Molecule | Two or more atoms bonded together that act as one unit, such as O₂. |
| Compound | A molecule made of two or more different types of atoms bonded together, such as H₂O. |
| Learning Goals | How You Showed It |
|---|---|
| Describe how all matter is built from atoms and organized on the periodic table (6.MS-PS1-1). | You zoomed from a gold coin down to a single atom and explored the periodic table to see how each type of atom has its own name, symbol, and mass. |
| Use models to show how atoms form molecules and compounds, and tell elements from compounds (6.MS-PS1-1). | You built O₂, H₂O, and CO₂ in the Matter Builder and sorted real substances into elements and compounds. |
Five questions covering everything you discovered, including substances for you to classify. Answer every question, then submit.
Atoms build every material you have ever touched. Offline challenges: grab a periodic table and write your initials using element symbols (for example, He-Ne or C-O). Or go on a kitchen compound hunt: find three labels listing H₂O (water), NaCl (salt), and CO₂ (in fizzy drinks), and sketch each as a model of bonded atoms. Which of your finds are elements, and which are compounds?