Key Idea: All atoms are extremely small.

Students are expected to know that:

  1. Individual atoms are much smaller than things that can be seen and even much smaller than very small things, such as dust, germs and other microorganisms, blood cells, and plant cells.
  2. This is true for all atoms.
  3. All atoms are so small that billions of them make up these small things.

Boundaries:

  1. The comparison with very small objects can be used to test students’ understanding of the relative size of atoms in relation to these objects. Students will not, however, be expected to know the actual size of atoms.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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AM025002

A grain of sand is bigger than an atom.

65%

78%

AM060003

An atom is smaller than the width of a hair, a cell in your body, and a germ.

63%

77%

AM026001

A blood cell is bigger than an atom.

63%

76%

AM061003

It would take millions of atoms to make a line across a small dot (about one millimeter in diameter).

38%

56%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

AMM124

A germ is smaller than an atom (AAAS Project 2061, n.d.).

17%

9%

AMM068

Cells are smaller than atoms (Tretter et al., 2006).

12%

7%

AMM125

A grain of sand is smaller than an atom (AAAS Project 2061, n.d.).

12%

8%

AMM001

Atoms/molecules are similar in size to cells, dust, or germs/bacteria (Lee et al., 1993; Nakhleh et al., 1999).

9%

8%

AMM104

The width of a hair is smaller than an atom (Tretter et al., 2006).

8%

6%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.