By Lily Mae, updated Aug 30, 2022
When a liquid turns into a solid, its properties shift in ways that fascinate scientists and students alike. These carefully designed experiments invite children to observe and explain the science behind freezing, melting, and the behavior of mixtures, making abstract concepts tangible and memorable.
Gather a set of common liquids—pure water, soda, orange juice, and lemonade—and have students predict which will solidify fastest. Pour each liquid into separate compartments of an ice tray and place the tray in the freezer. Check the tray at regular intervals, noting the elapsed time. When the first ice crystal forms, remove the tray and compare the remaining liquids. Pure water typically freezes first because it has the lowest solute concentration, which lowers its freezing point. Discuss how impurities and dissolved gases affect the freezing process.
Explore how different substances melt ice—a practical winter safety topic. Provide ice cubes on individual plates and offer three materials: table salt, sand, and kitty litter. Students sprinkle each onto a cube and record which melts quickest. Salt lowers the freezing point of water, so it melts ice most effectively, while sand and litter primarily provide traction.
Demonstrate density differences by mixing water and oil in clear containers. Initially, water settles at the bottom and oil rises. Freeze the mixture; the arrangement reverses because ice is less dense than liquid water. Extend the activity by adding soda, sugar water, or juice to oil and observing whether the separation changes when frozen. This shows how solute concentration and temperature influence density and phase behavior.
Create bi‑colored ice cubes by filling a tray halfway, adding food coloring, and freezing. Complete the tray with extremely cold water and refreeze. Place the cubes in warm water; watch the colored side lift, then flip again, repeating until the cube dissolves. The heavy, unheated top surface gradually becomes buoyant, causing the cube to rotate. Test the effect with mixed‑liquid cubes (half water/half soda, milk/juice) to see if the flipping phenomenon persists.
