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

Key Idea: There are differences in the spacing, motion, and interaction of atoms and molecules that make up solids, liquids, and gases.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students are expected to know that:

The particles of a gas (atoms or molecules) are much farther apart than the atoms or molecules of a liquid or a solid. Because atoms or molecules of a gas are so far apart they rarely come in contact with each other. In solids and liquids, the atoms or molecules are packed closely together.
Although the motion of atoms or molecules of a solid is severely restricted, the atoms or molecules are constantly moving back and forth in all directions with respect to a fixed position. In liquids, the motion of the atoms or molecules is limited but the atoms or molecules can still move rapidly back and forth with respect to a fixed point, around a fixed point, and past each other from one fixed point to another. Atoms or molecules of a gas move freely and spread out throughout the container they occupy.
Similar to the pushes and pulls between magnets, atoms or molecules also push and pull on each other.
1. In solids, the atoms or molecules pull strongly on each other and are linked together in rigid structures.
2. In liquids, the atoms or molecules pull less strongly on each other, are more loosely connected, and form less rigid structures.
3. In gases, the pull between atoms or molecules is so weak that they do not form structures.
Hardness, flow, and compressibility are macroscopic properties for which students are expected to know the molecular reason.
1. Solids are hard because the atoms or molecules are linked together tightly in rigid structures, not because the individual atoms or molecules are hard.
2. The atoms or molecules of liquids can easily move past each other from one fixed point to another but do not move apart from one another and that this is why liquids flow and take the shape of their container but solids do not.
3. Gases can be compressed because the atoms or molecules are not as close together as they could be, not because the individual atoms or molecules are soft.

Boundaries:

Students are not expected to know the nature of the bonds between atoms or between molecules.
They are not expected to know that atoms or molecules of a solid can sometimes move past each other.
Students are not expected to know the terms rotation, translation, and vibration.
They are not expected to know that plasma is a distinct state of matter, and they are not expected to know the properties of a plasma.

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
AM027003	Molecules are spaced farthest apart in a gas.	66%	76%
AM056003	The molecules of a gas are far apart from one another.	61%	69%
AM055002	The connection between the molecules of a solid are the strongest compared to the molecules of a liquid or a gas.	61%	71%
AM033003	Ice is harder than liquid water because the molecules of ice are linked more tightly together than the molecules of liquid water.	50%	66%
AM069002	The molecules of a gas are spread far apart throughout a sealed container.	47%	62%
AM068003	Gases can be compressed more easily than solids because the molecules of gases are farther apart than the molecules of solids.	39%	55%
AM057005	Liquid water takes the shape of a cup it is poured into but solid ice cubes do not, because the molecules of liquid water can easily move past one another but the molecules of solid ice cannot.	39%	48%
AM071002	Liquid candle wax flows but solid candle wax does not because the molecules of liquid candle wax can easily move past one another but the molecules of solid candle wax cannot.	35%	53%

Frequency of selecting a misconception
Misconception ID Number	Student Misconception	Grades 6–8	Grades 9–12
AMM032	Atoms or molecules of a solid are not moving (Lee et al., 1993; Novak & Musonda, 1991).	32%	30%
AMM118	Particles of a gas are closely packed with no empty space between them (Benson et al., 1993; Novick & Nussbaum, 1978).	32%	20%
AMM017	Atoms and molecules of a gas in a container are not uniformly distributed (Novick et al., 1981; Lee et al., 1993).	21%	18%
AMM016	The gas state of a substance weighs less than the liquid or solid state (Stavy, 1990).	17%	15%
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).	18%	10%
AMM128	The molecules of the gas state are the lightest and the molecules of the solid state are the heaviest (Griffiths et al., 1992).	15%	9%
AMM034	Atoms or molecules of a gas are not in motion (Novick et al., 1981).	8%	8%

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	Gases and liquids are made of molecules or inert atoms that are moving about relative to each other.