Student Handout: Connecticut Road Salt & Freezing Point Depression

Part 1: Engage (Anchoring Phenomenon)

Every winter, trucks cover Connecticut roads with thousands of tons of salt before and during snowstorms. But how does this actually stop ice from forming?

  1. Why does salt prevent ice from forming?
  2. Does the type of salt matter?
  3. How much salt is needed to effectively clear the roads?

Part 2: Explore (Simulation Investigation)

Use the Connecticut Road Salt simulation to explore freezing point depression.

  1. Initial Observations: Run the simulation with pure water. Note the freezing point and observe the molecular behavior.
  2. Variable Testing: Test different solutes (NaCl, CaCl₂, Sand) at various concentrations.
  3. Data Collection: Create a table to record the solute type, concentration, and the resulting freezing point.
  4. Micro-Level Interactions: Observe the micro-level view. How do the solute particles interact with the water molecules during freezing?

Part 3: Explain (Sensemaking)

Based on your data, explain the mechanism behind freezing point depression.

  1. Trend Analysis: What is the relationship between the concentration of a solute and the freezing point of water?
  2. Comparative Analysis: Why does CaCl₂ lower the freezing point more than NaCl at the same concentration?
  3. Evidence-Based Reasoning: Support your explanation with specific evidence from the simulation, focusing on the number of dissolved particles (the van ‘t Hoff factor, i).

Part 4: Elaborate/Evaluate (Argumentation & Modeling)

Develop a model or draft a scientific argument (CER format) that connects your observations to the broader scientific principles of intermolecular forces.