In this hands-on STEM investigation, students explore freezing point depression and phase changes by testing how adding different amounts of salt affects how quickly ice melts. Using real-world winter road safety as the context, students investigate why salt is spread on icy roads and how it changes the behavior of water at low temperatures.

Students measure ice mass and temperature over a set time period, compare salted and unsalted ice, and analyze how increasing salt amounts impacts melting. Through repeated trials, quantitative data collection, graphing, and a structured Claim–Evidence–Reasoning (CER) response, students connect experimental results to molecular-level explanations of phase change in a clear, engaging way.

This investigation blends physical science, chemistry, and real-world problem solving, allowing students to design fair tests, analyze patterns, and explain results using scientific evidence—just like real scientists and engineers.

What Students Will Learn

• How salt lowers the freezing point of water
• How phase changes occur below 0°C
• Why salted ice melts faster than unsalted ice
• How to design a fair scientific investigation
• How to support explanations using data and reasoning

Learning Targets

• Plan and carry out a controlled investigation with repeated trials
• Investigate how salt affects freezing and melting of ice
• Measure changes in ice mass and temperature over time
• Collect, graph, and analyze quantitative data
• Use evidence to explain freezing point depression and phase changes

What’s Included

Teacher Guide

Background science on freezing point depression, phase changes, and winter road safety; setup guidance; safety notes; classroom management tips; expected results; and common student misconceptions with fixes.

Student Packet

Driving question, hypothesis prompt, variables chart, step-by-step experimental procedure, structured data tables, graphing task, analysis questions, and a guided CER response.

Analysis & Answer Key

Sample data, expected patterns, completed data tables, graph examples, detailed scientific explanations, CER model responses, and common sources of error.

Rubric

Assesses experimental design, data accuracy, graphing quality, scientific reasoning, CER strength, collaboration, and safety.

Why Teachers Love It

• Strong real-world connection to winter road safety
• High student engagement with visible, measurable results
• Builds core lab skills: variables, measurement, graphing, CER
• Clear alignment with physical science and chemistry standards
• Low-prep, easy-to-manage, and highly structured
• Works well for winter units, phase change lessons, or sub plans

➡️ You can get this STEM as well as all my other ones in this series inside my STEM Investigations Growing Bundle. As more labs are added, the price will increase. CLICK HERE to have a look

Best For

Physical Science (phase changes, thermal energy), Chemistry (solutions, freezing point depression), STEM investigations, lab skills, graphing, CER writing, winter science units, and substitute-friendly lessons.

Materials Needed

Ice cubes (same size per group), clear cups or beakers, table salt, digital scale (grams), thermometer, timer or stopwatch, student packet (included).

Estimated Timing

• 1 class period for setup, testing, data collection, graphing, and CER
• Optional extension for error analysis or real-world application discussion

➡️ You can get this activity inside my STEM Investigations Growing Bundle.

I also have the following STEM Labs in My Store:

• Blow Cup Challenge STEM Lab
• Paper Table STEM Lab
• Pendulum STEM Lab
• Parachute STEM Lab
• Catapult STEM Lab
• Paper Airplane - Angle of Attack STEM Lab
• Bottle Flip STEM Lab
• Paper Helicopter STEM Lab
• Yeast Balloon STEM Lab
• Balloon Lift Design STEM Lab
• Candy Combustion Calorimetry STEM Lab
• Marble Ramp: Height vs Average Speed STEM Lab
• Clean Water Filtration STEM Lab
• Beetle Genetics STEM Lab
• Adaptations by Design - Extreme Environments STEM Lab
• Newton's 1st Law of Motion STEM Lab - Penny and Index Card - Inertia Test
• Newton's 2nd Law of Motion STEM Lab - Balloon Rocket
• Newton's 3rd Law of Motion STEM Investigation - Thrust vs Nozzle Size
• Electromagnet - Coil Turns vs Magnetic Strength
• Oobleck: Force vs Flow — Non-Newtonian Fluids
• Homemade Lava Lamp - Density & Gas Production - STEM Investigation
• Net Force STEM Investigation - Balanced vs Unbalanced Forces
• Thermal Insulation STEM Investigation – Keep Ice from Melting!
• Why Do Roads Get Salted? STEM Investigation — Lowering the Freezing Point

NGSS alignment

MS-PS1-4, MS-PS3-3, MS-PS3-4

Science & Engineering Practices: Planning and Carrying Out Investigations; Analyzing and Interpreting Data; Using Mathematics and Computational Thinking; Constructing Explanations; Engaging in Argument from Evidence

Assessment

Use the included rubric to score experimental design, procedure consistency, data accuracy, graphing quality, scientific reasoning, CER strength, collaboration, and safety.