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Massachusetts Comprehensive Assessment System

2011, High School Chemistry

  Question 44: Open-Response  
At sea level, water boils at 100°C. The boiling point of water varies with changes in air pressure, as shown in the diagram below.
This is a phase diagram that has pressure in atmospheres on the x-axis and temperature in degrees Celsius on the y-axis. The center of the x-axis is marked 1 atmosphere. The y-axis is divided in about thirds with 0 degrees Celsius marked on the first third and 100 degrees Celsius marked on the second third. The curve starts at 0 atmospheres and 0 degrees Celsius, curves up and to the right until about 0.3 atmospheres and 10 degrees Celsius. At that point the curve splits into a
  1. Based on the diagram, describe what happens to the boiling point of water as air pressure decreases.
  2. Use the kinetic molecular theory to describe the process of boiling.
  3. Use the kinetic molecular theory to explain why the boiling point of water is affected by pressure.

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 kinetic molecular theory and how it relates to the properties of gases, liquids, and solids and the behavior of matter as it undergoes phase transitions. The response correctly describes what happens to the boiling point of water as air pressure decreases. The response also correctly uses the kinetic molecular theory to describe the process of boiling and to explain why the boiling point of water is affected by pressure.
4
3
The response demonstrates a general understanding of the kinetic molecular theory and how it relates to the properties of gases, liquids, and solids and the behavior of matter as it undergoes phase transitions.
2
The response demonstrates a limited understanding of the kinetic molecular theory and how it relates to the properties of gases, liquids, and solids and the behavior of matter as it undergoes phase transitions.
1
The response demonstrates a minimal understanding of the kinetic molecular theory and how it relates to the properties of gases, liquids, and solids and the behavior of matter as it undergoes phase transitions.
0
Response is incorrect or contains some correct work that is irrelevant to the concept being measured.

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

High School Chemistry

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

Return to the MCAS 2011 Student Work Directory



Last Updated: March 29, 2004
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