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# Massachusetts Comprehensive Assessment System

## 2011, High School Chemistry

 Question 11: Open-Response Reporting Category: Solutions, Equilibrium, and Acid-Base TheoryStandard: 7.4 - Compare and contrast qualitatively the properties of solutions and pure solvents (colligative properties such as boiling point and freezing point). Antifreeze is mixed with water in a car’s radiator to help keep the solution from freezing. The graph below shows how the freezing point of a solution of antifreeze and water changes based on the percent of antifreeze in the solution.Based on the graph, estimate the percent of antifreeze in a solution of antifreeze and water that has the lowest freezing point.Compare the freezing point of 1 L of 40% antifreeze solution with the freezing point of 10 L of 40% antifreeze solution. Explain the reasoning for your answer.A car mechanic stated that a 50% antifreeze solution provides better protection for the radiator of a car than a 90% antifreeze solution. Is the mechanic’s statement correct or incorrect? Include data from the graph to support your answer.

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

ScoreDescription
4 The response demonstrates a thorough understanding of the properties of solutions and pure solvents. The response correctly estimates the percent of antifreeze that has the lowest freezing point. The response correctly compares the freezing point of a 1 L solution of 40% antifreeze with a 10 L solution of 40% antifreeze and explains the reasoning for the answer. The response identifies the mechanic’s statement as correct and includes data from the graph to support the answer.
4
3
The response demonstrates a general understanding of the properties of solutions and pure solvents.
2
The response demonstrates a limited understanding of the properties of solutions and pure solvents.
1
The response demonstrates a minimal understanding of the properties of solutions and pure solvents.
0
The 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.

Question 11:
Question 23:
Question 33:
Question 44:
Question 45: