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Massachusetts Comprehensive Assessment System

2013, High School Chemistry

  Question 23: Open-Response  
Particle models of four different types of matter are shown in the diagram below.
Model 1 shows a square containing circles joined in pairs. The pairs of circles are either both white or both black.
Model two shows a square containing circles. All the circles are white. The circles on the left side of the square are joined in pairs. The circles on the right side of the square are single circles.
Model three shows a square containing circles joined in pairs. All of the pairs of circles have one white circle joined to one black circle.
Model 4 shows a square containing circles joined in pairs. The top half of the square contains pairs of white circles. The bottom half of the square contains pairs of circles with one white circle joined to one black circle.
  1. Identify which of the four models best represents a pure compound. Explain your answer and give a specific example of a compound.
  2. Identify which of the four models best represents a homogeneous mixture. Explain your answer and give a specific example of a homogeneous mixture.
  3. Describe one method that could be used to separate a homogeneous mixture.

Scoring Guide and Sample Student Work
Select a score point in the table below to view the sample student response.

ScoreDescription
4 The response demonstrates a thorough understanding of the differences among pure substances, homogeneous mixtures, and heterogeneous mixtures. The response correctly identifies the particle models that correspond to a pure compound and to a homogeneous mixture, clearly explains the answers, and gives specific examples of each. The response also clearly describes one method that could be used to separate a homogeneous mixture.
4
3
The response demonstrates a general understanding of the differences among pure substances, homogeneous mixtures, and heterogeneous mixtures.
2
The response demonstrates a limited understanding of the differences among pure substances, homogeneous mixtures, and heterogeneous mixtures.
1
The response demonstrates a minimal understanding of the differences among pure substances, homogeneous mixtures, and heterogeneous mixtures.
0 Response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured.

Note: There are 2 sample student responses for Score Point 4.

High School Chemistry

Question 11: Bonding and Reactions
Question 23: Properties of Matter and Thermochemistry
Question 33: Bonding and Reactions
Question 44: Atomic Structure and Periodicity
Question 45: Solutions, Equilibrium, and Acid-Base Theory

Return to the MCAS 2013 Student Work Directory



Last Updated: June 17, 2016
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