Key Idea: 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.

Students are expected to know that:

  1. Note: The term “characteristic property” is used to emphasize that these properties are defining attributes that are independent of the amount of the sample, regardless of time, location, size, or shape.
  2. The term “substance” means a pure material that is made of the same matter throughout. This is in contrast to the common definition that equates substance with matter that could be made of either a single substance or a mixture of more than one substance. To make this explicit, the phrase “pure substance” is used in assessment items.
  3. A substance can be a solid, a liquid, or a gas.
  4. Every substance has a set of characteristic properties that are always the same for that substance, regardless of time, location, shape, or size.
  5. Furthermore, characteristic properties are consistent throughout a sample of a substance.
  6. Characteristic properties with which students should be familiar are boiling point, melting and freezing point, solubility (i.e. how much of the substance can dissolve in water), flammability (i.e. the ease with which a substance will catch on fire), odor, color, and density (i.e., that equal volumes of different substances have different masses).
  7. Weight, mass, volume, shape, length/width, texture, and temperature are not characteristic properties of substances and may change.
  8. The characteristic properties of a substance do not change when temperature and pressure remain the same.
  9. No two substances can have the same set of characteristic properties under the same conditions and that if two materials have even one different characteristic property, they are different substances.

Boundaries:

  1. Students are not expected to know that the properties of substance can be different at the nanoscale.
  2. They are not expected to know the formula for density (density = mass/volume).
  3. Students are not expected to know that the atomic mass of a substance is a characteristic property.
  4. They are not expected to know whether specific materials are or are not pure substances.
  5. Because some properties do change with changing conditions (e.g., changing atmospheric pressure affects boiling point) all assessment items will make comparisons between substances where it is clear that the conditions, such as temperature and pressure, are constant.
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
Select This Item for My Item Bank

SC095003

To help identify a metal, you could determine its density and compare it to the density of other metals.

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SC095002

To help identify a metal, you could determine its melting point and compare it to the melting point of other metals.

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SC064007

Two liquids with the same density and color but different boiling points are different substances. (This item uses a table that lists properties of the liquids.)

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SC063004

To identify a liquid, you could determine the boiling point of the liquid and compare it to the boiling points of other liquids.

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SC057008

Two solids with the same melting point and color could be the same substance. (This item uses a table that lists properties of the solids.)

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SC044004

If a piece of wax is removed from a ball of wax, the mass of the ball of wax would change but its melting point would stay the same.

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SC057007

Two solids with the same melting point and color could be the same substance. (This item uses a table that lists properties of the solids.)

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SC046005

How much of a substance dissolves in water is a characteristic property of the substance.

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SC100003

Two liquids with the same flammability, boiling point, and color could be the same substance. (This item uses a table that lists properties of the solids.)

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SC064008

Two liquids with the same density and color but different boiling points are different substances. (This item uses a table that lists properties of the liquids.)

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SC100004

Two liquids with the same boiling point and color could be the same substance. (This item uses a table that lists properties of the liquids.)

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SC099002

Determining the mass of a liquid and comparing its mass to the mass of other liquids will NOT help you identify the liquid.

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SC061004

Smelling two liquids can help a student determine if the liquids are the same substance.

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Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8
Grades
9–12

SCM081

Density is not a characteristic property of a pure substance.

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SCM080

Freezing point is not a characteristic property of a pure substance.

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SCM079

Melting point is not a characteristic property of a pure substance.

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SCM078

Boiling point is not a characteristic property of a pure substance.

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SCM077

Flammability is not a characteristic property of a pure substance.

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SCM076

Color is not a characteristic property of a pure substance (AAAS Project 2061, n.d.).

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SCM069

The melting point of a substance is dependent on the amount of substance. For example, the melting point of a ball of wax will change if a piece of wax is removed from the ball (AAAS Project 2061, n.d.).

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SCM061

Shape is a characteristic property of a substance (AAAS Project 2061, n.d.).

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SCM060

Length is a characteristic property of a substance (AAAS Project 2061, n.d.).

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SCM059

Width is a characteristic property of a substance (AAAS Project 2061, n.d.).

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SCM058

Volume is a characteristic property of a substance (DeBoer et al., 2009).

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SCM057

Mass/weight is a characteristic property of a substance (DeBoer et al., 2009).

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SCM054

If most of the listed characteristic properties are the same, the substances are the same (AAAS Project 2061, n.d.).

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SCM053

If two substances share one characteristic property, they are the same substance (AAAS Project 2061, n.d.).

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SCM023

Temperature is a characteristic property of the substance (Thomaz et al., 1995).

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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.