Science Assessment ~ Ideas ~ All matter is made up of atoms.

Key Idea: When heated, solids can change into liquids and liquids can change into gases. When cooled, gases can change into liquids and liquids can change into solids. These changes of state can be explained in terms of changes in the proximity, motion, and interaction of atoms and molecules.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students are expected to know that:

When the temperature of a liquid decreases, the average speed of the atoms or molecules decreases and, as a result, the pull that exists between the atoms or molecules is strong enough to link them together as a solid.
When the temperature of a solid increases, the average speed of the atoms or molecules increases and the pull between the atoms or molecules is no longer strong enough to hold them together as a solid; the atoms or molecules are now more loosely connected as a liquid.
When the temperature of a gas decreases, the average speed of the atoms or molecules decreases and, as a result, the pull that exists between the atoms or molecules is strong enough to loosely connect them together as a liquid.
When the temperature of a liquid increases, the average speed of the atoms or molecules increases and the pull between the atoms or molecules is no longer strong enough to hold them together as a liquid. In this case, the pull between atoms or molecules is so weak that they are no longer connected to each other, but rather they exist as a gas.
At the boiling point and freezing point, atoms or molecules from anywhere in the substance can enter the gas state and solid state, respectively. Because of this, the bubbles that form when the substance is boiling are atoms or molecules of that substance in the gaseous state.
Evaporation or condensation can also occur independent of temperature; i.e., at any temperature there are some atoms or molecules that may move from one state to another at the surface of a substance. This also includes atoms or molecules on the surface of a solid that can enter the gas state.
A substance is made up of the same type of atom or molecule regardless of whether it is in the solid, liquid, or gas state. There is no change in the identity of the atoms or molecules during a change of state; only the arrangement, motion, and interaction of the atoms or molecules change.
Atoms or molecules are not destroyed during a change of state.
Any change of state is reversible.

Boundaries:

Although changes of state can be caused by changes in either temperature or pressure, students are only expected to know the effects of changes in temperature.

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
AM035004	When a piece of solid wax is heated, it becomes a liquid and the wax molecules become more loosely connected to each other.	48%	65%
AM028003	When a substance changes from a liquid to a solid, the molecules of the substance connect more strongly to one another.	44%	60%
AM036003	Water spilled on the floor will eventually disappear because the water molecules become a gas and are now part of the air.	46%	53%
AM062004	As water boils, the molecules become separated from each other.	38%	50%
AM065003	Wet jeans hung on a clothesline eventually dry because the water molecules move faster and become part of the air.	38%	47%
AM067006	As a substance changes state, the connection between molecules of the substance changes.	37%	48%
AM031004	The bubbles that form when water boils are made of water molecules.	13%	18%

Frequency of selecting a misconception
Misconception ID Number	Student Misconception	Grades 6–8	Grades 9–12
AMM061	The molecules of a substance break down into individual atoms when the substance evaporates. During evaporation, water breaks down into hydrogen and oxygen (Bar et al., 1991; Bar et al., 1994).	39%	37%
AMM049	The molecules of a substance break down into individual atoms when the substance boils. For example, molecules of water become atoms of hydrogen and oxygen when water boils (Osborne et al., 1983; Renstrom et al., 1990).	36%	34%
AMM051	When water boils, the bubbles formed during boiling contain air, not water in the gas state (Osborne et al., 1983; Renstrom et al., 1990; Bar et al., 1991; Johnson, 1998a; Chang, 1999).	29%	26%
AMM038	Heat is made of "heat molecules" (Berkheimer et al., 1988).	25%	17%
AMM043	Molecules change shape during a phase change (Novak et al., 1991; Griffiths et al., 1992).	19%	19%
AMM015	Observable properties of the state are attributed to the individual molecules (e.g., molecules in a solid are hard; molecules move in gases and liquids, but not in solids; or the molecules of the substance change from soft to hard when a liquid freezes) (Lee et al., 1993).	23%	12%
AMM047	The identity of the molecules of a substance changes during a phase change (Lee et al., 1993).	21%	14%
AMM045	Molecules change weight/mass during a phase change (Griffiths et al., 1992).	19%	14%
AMM133	Matter is destroyed during melting (AAAS Project 2061, n.d.).	15%	10%
AMM044	Molecules change size during a phase change (Novak et al., 1991; Griffiths et al., 1992).	11%	9%
AMM132	Matter is destroyed during boiling (AAAS Project 2061, n.d.).	11%	7%
AMM131	Matter is destroyed during evaporation (Bar & Galili, 1994; Bar & Travis, 1991; Lee et al., 1993; Osborne & Cosgrove, 1983)	11%	7%
AMM063	When water evaporates from an object, that water is absorbed into the object (Osborne et al., 1983; Bar et al., 1991; Bar et al., 1994).	7%	7%

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	In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations.
PS1.A MS	The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.
ESS2.C MS	Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land.