By Jordan Meyers
Updated Aug 30, 2022
Image credit: Jupiterimages/Photos.com/Getty Images
Incorporating hands‑on investigations into everyday lessons helps young learners grasp scientific concepts. Ordinary table salt is a safe, inexpensive tool that opens a world of experiments for second‑graders—experiments that can even be replicated at home by parents.
Have students compare how salt affects the freezing point of water. Fill two disposable cups ¾ full with tap water; add 1 tablespoon of salt to one cup. Place both cups in the freezer and check every 20 minutes. Unsalted water typically freezes at 32°F (0°C), whereas the salted solution may require temperatures as low as –5.8°F (–20°C) to solidify. This demonstrates that salt lowers the freezing point—a fundamental principle of colligative properties.
Show the difference between a mixture and a solution using salt, Italian seasoning, and hot water. Dissolve 2 teaspoons of salt in hot water until completely transparent. In a second bowl, add 2 teaspoons of Italian seasoning to hot water; the seasoning remains visible and does not dissolve. The first example is a homogeneous solution; the second is a heterogeneous mixture.
Explore how salt changes water’s density. Use two bowls filled halfway with water; add 6 tablespoons of salt to one. Drop objects such as coins, marbles, pencils, fruit pieces, and small rocks into each bowl. Note which items float or sink. When an item that sinks in plain water floats in the salted water, record how much salt was needed. The increased density makes floating easier—illustrating the relationship between solute concentration and buoyancy.
Demonstrate that salt lowers the melting point of ice. Place an ice cube in each of two bowls. Sprinkle 1 teaspoon of salt on one cube and 1 teaspoon of sugar (or cinnamon) on the other. Observe which cube melts faster. The salted ice will melt more quickly, showing that solutes disrupt the crystalline lattice of ice. This experiment also introduces the concept that water can exist as solid, liquid, and gas, as seen when boiling water produces steam.
