Science Assessment ~ Ideas ~ A pure substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the amount of the substance and can be used to identify it.

Key Idea: Many substances react chemically in predictable ways with other substances to form new substances with different characteristic properties.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students are expected to know that:

When substances react chemically one or more new substances are formed.
If a new substance does not appear, a chemical reaction did not occur.
The products of a chemical reaction can be identified as new substances because each product has different characteristic properties from the original substances under the same conditions.
Liquids, solids, or gases can be reactants or products in chemical reactions.
It is possible for a single substance to undergo a chemical reaction, such as when the substance is heated or an electrical current flows through the substance.
It is not true that all chemical reactions are irreversible.

Boundaries:

Students are not expected to know that chemical reactions involve the rearrangement of atoms into new molecules. This idea is addressed in a later idea (Idea D).
Students are also not expected to know that nuclear reactions are not chemical reactions nor why nuclear reactions are not chemical reactions. Nuclear reactions are addressed in later ideas (4E/H6* and 4G/H6*)
By “predictable ways,” we mean that the same products will be formed when the same reactants are combined regardless of location and experimental set-up. Students are not expected to predict what the products of a reaction will be.
Students are expected to know that the original substances in a chemical reaction are called reactants and the resulting substances are called products but they will not be assessed on these definitions.

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
SC069007	When a chemical reaction occurs, the characteristic properties of the products are different than the characteristic properties of the reactants. (This item used a table to show the properties of the substances.)	55%	65%
SC072004	Chemical reactions produce solids, liquids, or gases.	67%	69%
SC072003	Chemical reactions produce solids, liquids, or gases.	63%	67%
SC049003	A chemical reaction always results in the formation of a new substance, which can be a solid, liquid, or gas.	58%	62%
SC029003	Forming a white solid by mixing two clear liquids is an example of a chemical reaction.	51%	59%
SC101003	Bubbles of gas forming as a seashell is placed in vinegar is an example of a chemical reaction.	51%	59%
SC071003	The surface of a copper penny changing color after being in a drawer for years is an example of a chemical reaction.	40%	52%
SC065004	Burning a marshmallow is an example of a chemical reaction.	35%	48%
SC067003	When two liquids are mixed together and a solid forms, the solid is a new substance that was formed during a chemical reaction between the two liquids.	37%	41%
SC073002	Some chemical reactions can be reversed.	16%	24%

Frequency of selecting a misconception
Misconception ID Number	Student Misconception	Grades 6–8	Grades 9–12
SCM070	A chemical reaction always happens when two substances are combined together (AAAS Project 2061, n.d.).	18%	16%
SCM040	Chemical reactions involve only the production of gas (Cavallo et al., 2003).	11%	13%
SCM039	Chemical reactions involve liquids only (Cavallo et al., 2003).	13%	11%
SCM063	Chemical reactions occur between solids and liquids but not between solids and gases (AAAS Project 2061, n.d.).	12%	10%
SCM037	All chemical reactions are inherently dangerous (Cavallo et al., 2003).	11%	11%
SCM056	A chemical reaction always happens when two liquids are combined together (DeBoer et al., 2008).	15%	9%
SCM062	A solid substance is always formed during a chemical reaction (DeBoer et al., 2008).	9%	8%
SCM002	A chemical reaction must take place in a laboratory (Herrmann-Abell et al., 2009).	8%	7%
SCM038	Chemical reactions involve two reactants (Cavallo et al., 2003; Eilks et al., 2007).	66%	58%
SCM036	A chemical change is irreversible (Cavallo et al., 2003; Calik et al., 2005).	36%	34%
SCM020	A chemical reaction occurs when a substance dissolves (Novak et al., 1991; BouJaoude, 1992; Abraham et al., 1994; Ahtee et al., 1998; Stavridou et al., 1998; Valanides, 2000; Eilks et al., 2007)	29%	21%
SCM019	A chemical reaction occurs during a change of state (Hall, 1973; Novak et al., 1991; BouJaoude, 1992; Ahtee et al., 1998; Stavridou et al., 1998).	19%	16%

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.

NGSS Statements
Code	Statement
PS1.A MS	Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.
PS1.B MS	Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.