Key Idea: When substances interact to form new substances, the atoms that make up the molecules of the original substances rearrange into new molecules.

Students are expected to know that:

  1. During a chemical reaction the atoms that are linked together in molecules (or arranged in other patterns such as arrays and crystals) rearrange to make new molecules.
  2. If the atoms are not rearranged, then a chemical reaction has not occurred.
  3. New substances are made of the same kinds of atoms as the original substances (i.e., the atoms themselves did not change during the reaction).

Boundaries:

  1. The idea that the number of each kind of atom stays the same will be assessed under Idea H (conservation of matter).
  2. Students are not expected to know the term “bond” or how chemical bonds are formed or broken during chemical reactions.
  3. They are not expected to know that during chemical reactions, atoms are not turned into energy.
Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

M002

During a chemical reaction, the molecules of any ending substance must always include every type of atom from the starting molecules.

See the Original Project

SCM026

The atoms of the reactants of a chemical reaction are transformed into other atoms (Andersson, 1986).

See the Original Project

SCM025

The reactants and products of a chemical reaction are different and independent of each other. There is no recognition of a change of one sample to the other (Johnson, 2000b).

See the Original Project

SCM021

After a chemical reaction, the product is a mixture in which the old substances persist, and is not a new substance (Johnson, 2000b; Solomonidou & Stavridou, 2000).

See the Original Project

SCM016

The products of a chemical reaction, though unseen, must have somehow existed from the start in another location, such as in the air or inside the reactants (Andersson, 1986; Solomonidou et al., 2000).

See the Original Project

SCM015

Substances can change their characteristic properties but maintain their identity (Pfundt, 1982). The products of a chemical reaction are the same substances as the reactants but with different properties (Solomonidou et al., 2000).

See the Original Project

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.