Work Sample & Commentary: Exothermic/Endothermic Reactions
The task
This experiment was a modification of an experiment in the text Chemistry: Visualizing Matter (Holt, Rhinehart & Winston). In this activity, students were asked to design an experiment to prove whether a worker’s claim that he was burned by a mixture of two cleaning fluids was true. This assignment was given to a Regent chemistry class.

Circumstances of performance
This sample of student work was produced under the following conditions:
alone in a group
in class as homework
with teacher feedback with peer feedback
timed opportunity for revision

This work sample illustrates a standard-setting performance for the following parts of the standards:
c Physical Sciences Concepts: Chemical reactions.
a Scientific Connections and Applications: Big ideas and unifying concepts.
a Scientific Thinking: Frame questions to distinguish cause and effect; identify and control variables.
b Scientific Thinking: Use concepts from Science Standards 1 to 4.
a Scientific Tools and Technologies: Use technology and tools.
a Scientific Communication: Represent data and results in multiple ways.


What the work shows

c Physical Sciences Concepts: The student produces evidence that demonstrates an understanding of chemical reactions such as every day examples of chemical reactions….
In the statement of purpose the student states that the reaction between sodium hydroxide(NaOH) and hydrochloric acid(HCl) involved heat change.
This understanding is also expressed in the hypothesis, which states that the mixture will produce sufficient heat to cause a burn.

a Scientific Connections and Applications: The student produces evidence that demonstrates understanding of big ideas and unifying concepts, such as…cause and effect.
The question clearly indicates that the student is looking for a cause and effect relationship.
The student determined that the mixture could cause a burn because of the heat generated during the reaction.
The student states that the concentration of sodium hydroxide remaining unreacted was too small to cause a chemical burn.

a Scientific Thinking:The student frames questions to distinguish cause and effect; and identifies and controls variables in experimental and non-experimental research settings.
The student frames the question appropriately.
A review of the formulae in the “Analysis and Interpretation of Results” makes it very clear that the student identified and controlled variables, both in the experiment itself and in the follow-up analysis.

b Scientific Thinking: The student uses concepts from Science Standards 1 to 4 to explain a variety of observations and phenomena.
Throughout the “Analysis and Interpretation of Results” the student uses physical science concepts from c expressed as formulae.
The student expresses concepts from c in the “Related Background Information” section, and used them to develop the hypothesis.
a Scientific Tools and Technologies: The student uses technology and tools (such as traditional laboratory equipment…) to observe and measure objects…and phenomena, directly, indirectly, and remotely, with appropriate consideration of accuracy and precision.
The materials list and the “Experimental Procedure” section make it clear that the student used a graduated cylinder, a calorimeter, and a Celsius thermometer.

a Scientific Communication: The student represents data and results in multiple ways, such as numbers [and] tables…and selects the most effective way to convey scientific information.
Throughout the “Analysis and Interpretation of Results” section, the student conveys scientific information through the use of formulae.
The student records data in a table format.