MIT Massachusetts Institute of Technology

How Big Is a Mole? Do We Really Comprehend Avogadro’s Number?

Dr. Jessica Silverman
Alan D. Crosby
Newton South High School
Newton, Massachusetts

With Maia Fefer, student

The unit “mole” is used in chemistry as a counting unit for measuring the amount of something. One mole of something has 6.02×1023 units of that thing. The magnitude of the number 6.02×1023 is challenging to imagine. The goal of this lesson is for students to understand just how many particles Avogadro's Number truly represents, or, how big is a mole.  This lesson is meant for students currently enrolled in a first or second year chemistry course. This lesson is designed to be completed within one approximately 1 hour class; however, completion of optional activities 4 and 5 may require a longer class period or part of a second class period.  This lesson requires only pencil and paper, as the activities suggested in this video place an emphasis on helping students develop their “back of the envelope” estimation skills.  In fact, calculators and other measuring devices are explicitly discouraged. However, students may require additional supplies (poster board, colored pencils, markers, crayons, etc.) for the final optional/assessment activity, which involves creating a poster to demonstrate the size of a mole of their favorite macroscopic object.


単位の「モル」は、あるものの量を計るための計測単位として化学で使われています。あるものの1モルは、そのものの6.02×1023 個あることになります。数字6.02×1023 の大きさは想像しがたいものがあります。この授業の目標は、生徒さんにアボガドロ数が真にどれくらいの数の分子を示しているか、すなわちモルがどれくらい大きいのか理解させることにあります。この授業は、現在化学の授業を始めて履修中の生徒か、2年目に履修している生徒向けとなっています。この授業は約一時間で終えられるようになっています。しかし、オプションとなっているアクティビティ4と5については、もっと授業時間が必要かもしれませんし、2時間目の一部を当てる必要があるかもしれません。このビデオで提案されているアクティビティは、生徒さんの「概算」スキルの発達を促すことに重きが置かれていますので、この授業では鉛筆と紙だけが必要になってきます。実際、計算機や他の計測器は使用禁止となっています。しかし、生徒さんは最後のオプションとなっている評価アクティビティには追加の教材(ポスター用ボード、色鉛筆、マーカー、クレヨンなど)が必要になってくるかもしれません。この最後のアクティビティでは、生徒たちが気に入っている巨視的な物体のモルでの大きさを表現するポスターを作成します。

Jessica holds a B.S. in chemistry from MIT and a Ph.D. in molecular microbiology from the Tufts University School of Medicine.  She has three years of teaching experience at the graduate level and one year at the high school level.  You can learn more about Jessica’s chemistry class through her website:

Alan instructed chemistry for nearly 30 years at the university level, most recently at Boston University, before transitioning to teaching at Newton South.  His thesis focus was on quantum chemistry—however, with a rich experimental background, he ran the numerous laboratory courses at Boston University.  He has been involved in chemical education his entire career, specifically working with high school chemistry teachers since 1980. He maintains an active website for his current classes at:

This famous film, “Powers of Ten”, takes viewers on a 9-minute adventure in magnitudes.

This 4-minute TED Ed lesson provides another look at “How Big Is a Mole?”

This site, sponsored by LearnChemistry: Enhancing Learning and Teaching, provides a comprehensive list of resources for learning about moles.

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This Lesson is in the following clusters: Chemistry Mole