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Ice Cold
Examples of Student Work
Contributed by: Connecticut Academic Performance Test (CAPT)

Item 1
This item assesses students' understanding of the need to conduct a controlled experiment when investigating the effect of one variable on another. The purpose of this experiment is to determine which form of salt, table salt or rock salt, is better for melting ice. In this group's experiment the third beaker containing only ice water serves as a control. The control is used to compared the freezing point of the ice without either type of salt. (Students may note that a control is not necessary for comparing the two salts.)

CAPT Framework
Experimentation: Design and conduct appropriate experiments.

Item 2
This item assesses students' understanding of what constitutes a complete and appropriate experimental design. In this case, students do not have all of the information that they need to replicate the experiment. Some of the additional information that students would need to know includes how much of each type of salt, ice, and water were used, the initial temperature of the contents of the beakers, the temperature of the surroundings, how well the components were mixed, etc.

CAPT Framework
Experimentation: Design and conduct appropriate experiments.

Item 3
This item assesses students' ability to draw conclusions based on data and to consider the validity of the conclusions. While more ice appears to have melted in the beaker containing rock salt, the conclusion should be strongly questioned. It is uncertain whether important variables have been controlled such as the initial mass of the ice, salt, and beakers, the exposed surface of the ice cubes, and the distribution of the salts. The difference in the mass of the two beakers and their contents at the end of the experiment is not very large. In addition, some of the salts may have been poured off with the melted water.

CAPT Framework
Experimentation: Make, record and interpret observations/Draw conclusions and discuss their validity.

Item 4
This item assesses students' understanding of what constitutes a complete and appropriate experiment. In this case, the group of students could have improved their experiment by determining the initial mass of the beakers, ice and salts to make sure they were equal and by controlling other important variables. They could have measured the volume of the water poured off. In addition, an appropriate control could have been used and the group could have carried out the experiment several times.

CAPT Framework
Experimentation: Design and conduct appropriate experiments.


Sample Student Responses for Experimentation Questions: "Ice Cold"

There are several examples for each score point ranging from 3 down to 0. Explanations of the scores were written by staff from the Division of Teaching and Learning at the Connecticut State Department of Education who conducted training and scoring of field tested events.




Component
Score
Commentary
Question 1
(3)
This response correctly identifies the beaker of ice water without salt as the control in the experiment. The response also explains the purpose of the control in this experiment ("They used this so they knew the difference between the temperature of the ice with salt and without"). It is correct and contains elaboration.



Component
Score
Commentary
Question 1
(3)
This response correctly identifies the beaker of ice water without salt as the control in the experiment. The response also explains the purpose of the control in this experiment ("They would probably then compare the control with the actual experiment in order to see what effect [time, temperature, etc.] the salts had on the melting of the ice"). It is correct and contains elaboration.

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