What is an atom?

Author(s): Linda Akiyama and Ranyee Chiang

Lesson Overview

Grade level(s):

Elementary School (K-5), Grade 3, Grade 5


FOSS-Related, Physical Science



Big ideas(s):

An atom is the smallest particle of an element that is still an element.  If you cut an atom of aluminum, you will no longer have aluminum.

Vocabulary words:

Introduced during the lesson:

Matter - All the stuff of the universe is made of matter.  Anything that takes up space.

Element - A type of atom.  There are 118 types of atoms in the periodic table.

Atom - the smallest part of an element that is still that element.  (If you cut one atom of an element, it will no longer be that element.)

What you need:

2 inch squares of aluminum (one for each student), scissors (one for each student)


Each student will have his or her own piece of aluminum and pair of scissors.  The teacher will lead the entire class together through the activity.



Time needed:

Total:  45 minutes

Introduction:  10-15 minutes

Activity: 10-15 minutes

Discussion: 10 minutes

Time for student questions: 10 minutes 

Author Name(s): 
Linda Akiyama and Ranyee Chiang

The students will repeatedly cut a piece of aluminum foil into smaller and smaller pieces to model the process of how you can break a substance down from a large number of atoms to a single atom.  This activity is meant to supplement the introduction to atoms on Foss Matter and Energy, Investigation 4: Changing Matter, Part 2: Melting and Evaporation, page 183.

Learning goals/objectives for students: 

Even though we cannot cut the aluminum to be a single atom, the students will understand that if they have better tools, they would be able to continue the cutting process to get one atom of aluminum.  The students will also understand that if they could cut one atom of aluminum, they will no longer have aluminum.

Getting ready: 

Write out the definitions for "matter," "element," and "atom" on pieces of paper that eventually can be displayed in the room during and after the activity.  (See vocabulary section)

Lesson Implementation / Outline


Introduce “matter”

Using the definition that is written up, introduce that matter is…

Introduce aluminum and elements

We are going to be working with a substance called aluminum.

  • Aluminum comes in different shapes and forms. This aluminum is rolled out thinly so it is easy to cut
  • Aluminum is one of the elements that are on our periodic table.  Introduce the definition of elements.
  • From the evidence that scientists have gathered so far, they believe that all the stuff in our world is made up of one or more of the elements listed on this table
  • Sometimes, substances are made up of only one element like aluminum.  Other times, substances are made up of multiple elements combined together, like wood or our bodies. 
  • We are going to use aluminum to help us better understand what an atom is.
  1. Each student has one piece of aluminum.  Tell them that each piece of aluminum is made up of a lot of aluminum atoms.
  2. Have them cut their piece of aluminum in half.  They keep one half.  They ball up the other half and put it to the side.
  3. Ask the students if the remaining half is still aluminum, even though we cut it in half.
  4. Repeat steps 2 and 3 a few times until the students understand that when we cut the aluminum in half with scissors, we still have a substance that is aluminum.
  5. When the students understand this idea, have them continue to repeat the process on their own until they have a tiny piece of aluminum remaining.

Even though the aluminum is very small, we still have aluminum and it is still made up of many atoms.  With our tool (scissors), we can only make aluminum this small.  If we had even better tools, we’d get to the point you have one atom of aluminum.  The smallest piece of aluminum is one atom of aluminum.  If you cut one atom of aluminum further, the pieces won’t be aluminum.

Go over definitions that you have prepared for an atom.

Allow the students to ask "wondering questions." 

Checking for student understanding: 

When cutting the aluminum multiple times, the teacher should ask different students whether we still have aluminum after we've cut it.

After going over the definition for an atom, ask the students if you could have 1 atom of oxygen (or any other element) and you could cut it, would you still have oxygen.

Extensions and Reflections

Extensions and connections: 

Math - How small is an atom?

1 atom of aluminum is .000000025 cm. long

If you could line up aluminum atoms, one right next to the other in a straight line one centimeter long, it would take about 40,000,000 aluminum atoms to make the line.

If you wanted to cover a centimeter square with atoms, each right next to each other, with no space in between, it would take about 1,600,000,000,000,000 atoms.

Difference between different types of atoms:

An atom of aluminum will be like all the other atoms of aluminum. But an aluminum atom differs in some ways from the atoms of a different element. We can tell the difference between an atom of aluminum and an atom of gold or an atom of oxygen.

Can you cut the tiny piece of aluminum more:

Have each students use a microscope, magiscope or magnifying glass to look at their tiniest piece and see that if we had better tools, we could still cut the aluminum into tinier pieces.

NGSS Topics
Kindergarten through Grade 5: 
NGSS Disciplinary Core Ideas
NGSS Performance Expectations
NGSS Performance Expectations: 
NGSS Science and Engineering Practices
NGSS Science and Engineering Practices: 
NGSS Crosscutting Concepts
NGSS Crosscutting Concepts: 

Standards - Grade 3

Physical Sciences: 
1. Energy and matter have multiple forms and can be changed from one form to another. As a basis for understanding this concept:
h. Students know all matter is made of small particles called atoms, too small to see with the naked eye.
i. Students know people once thought that earth, wind, fire, and water were the basic elements that made up all matter. Science experiments show that there are more than 100 different types of atoms, which are presented on the periodic table of the elements.