Science Assessment ~ Items ~ SC075004

A student placed a piece of bread in a plastic bag. He sealed the bag so that nothing could get in or get out. After two weeks, he noticed mold growing on the bread. (Note that the mold’s weight increases as it grows.)

The student weighed the bag and its contents before and after the mold started growing. After two weeks, did the bag and its contents weigh the same, more, or less than it did before the mold started growing?

The bag and its contents weighed the same.
The bag and its contents weighed more.
The bag and its contents weighed less.
More information is needed to tell if the weight of the bag and its contents changed.

Explain why you selected the answer choice you did. Be as complete as you can and include science ideas in your explanation.*

Details
Performance
NGSS

Topic

Substances, Chemical Reactions, and Conservation of Matter

Correct Answer

Explanation Scoring Rubric

Reasoning – States the relevant general principles and links them to the claim (5 points)

States or uses the general principle that the bag was sealed, so matter can’t get in or out. (Closed system)
States the general principle that matter is not created or destroyed during chemical reactions. (Conservation)
States or uses the general principles of conservation and closed system in terms of atoms.
States or uses the general principle that the mass of an atom does not change.
Provides a mechanism that links the general principles to the answer choice selected (claim): Although new substances are produced as the mold grows, the new substances are produced by rearranging atoms that were already in the sealed bag. Hence, the bag and its contents weighed the same.

*The prompt shown for the explanation tier reflects revision following its use in the Year 3 study for which student results are shown.

Misconceptions

Answer Choice: B: SCM042: If something grows in a closed system, the total mass of the system increases. For example, when a tree grows in a closed system, the total mass of the system increases (Mitchell et al., 1984) or when mold grows in a closed system, the total mass of the system increases (DeBoer et al., 2009).

Pre-Test

Pre-Test

Post-Test (Treatment)

Post-Test

Distribution of Multiple Choice Responses

Chart showing distrubtion of responses for Item SC075004

Multiple Choice Points Earned

Group	Correct	Total	Percent
Overall	66	376	18%
Grades
6–8	66	376	18%
9–12	N/A	N/A	N/A
Gender
Male	43	206	21%
Female	23	170	14%
Primary Language
English	65	348	19%
Other	1	28	4%

Explanation Points Earned

Group	Earned	Possible	Percent
Overall	74	1890	4%
Grades
6–8	74	1890	4%
9–12	N/A	N/A	N/A
Gender
Male	56	1035	5%
Female	18	855	2%
Primary Language
English	73	1750	4%
Other	1	140	1%

View data table

Distribution of Multiple Choice Responses

Multiple Choice Points Earned

Group	Correct	Total	Percent
Overall	217	378	57%
Grades
6–8	217	378	57%
9–12	N/A	N/A	N/A
Gender
Male	132	207	64%
Female	85	171	50%
Primary Language
English	209	350	60%
Other	8	28	29%

Explanation Points Earned

Group	Earned	Possible	Percent
Overall	376	1890	20%
Grades
6–8	376	1890	20%
9–12	N/A	N/A	N/A
Gender
Male	223	1035	22%
Female	153	855	18%
Primary Language
English	364	1750	21%
Other	12	140	9%

View data table

Disciplinary Core Ideas: PS1.B No matter what reaction or change in properties occurs, the total weight of the substances does not change. (Boundary: Mass and weight are not distinguished at this grade level.)

Science Assessment

Item SC075004: When mold grows on a piece of bread in a sealed container, the bag and its contents weigh the same before and after the mold start growing.