What Melts Ice Fastest? Salt, Sugar and Sand Compared

Which melts ice fastest: salt, sugar or sand? Most children guess salt, and they’re right, but the experiment is more interesting than the answer, because it needs a careful fair test and it leads to a real-world conclusion.

What you need

Identical ice cubes from the same tray (4 per team)
Table salt, sugar and sand, one teaspoon each
Four small plates or cups, labelled: salt, sugar, sand, nothing
A measuring cup with millilitre markings, or a kitchen scale, and a timer

The method

Predict. Which will melt the most ice in 20 minutes? Why?
Put one cube on each plate. Sprinkle one teaspoon of each material on its cube. Leave one plain as the control.
Start the timer and leave all four in the same spot.
After 20 minutes, pour the meltwater from each plate into the measuring cup and record the millilitres.
Repeat at least twice and compare.

Keep the same: cube size, amount of material, room, time. Change: the material.

What usually happens

The salted cube melts the most, and it’s often obvious within a few minutes, with a pool of water and a pitted cube. Sugar melts a bit more than the plain cube. Sand does about the same as nothing, though dark sand can speed melting a little in sunlight by absorbing heat.

The science

Salt and sugar both dissolve in the thin layer of water on the ice. Dissolved particles lower the freezing point of water, so the ice melts at a temperature below 0 °C. Salt splits into two kinds of particle when it dissolves, which makes it more effective per spoonful than sugar. Melting takes heat from the surroundings, so the mixture gets colder. Sand doesn’t dissolve, so it can’t do this.

This is why road crews spread salt on icy roads, and sand for grip rather than melting. Salt works down to a certain temperature, and in very cold weather other treatments are needed.

Use the evidence

A good follow-up: “If you ran a drinks stall on a hot day, would you add salt to your ice?” The data helps you decide: salted ice melts faster, but it also gets colder. A salty ice bath chills a drink faster than plain ice, even though the ice melts sooner.

Try What melts ice fastest? from Winter Science: Ice, Snow and Staying Warm, or the summer version, What melts ice fastest on a hot day? from Keep It Cool. Younger children enjoy Why does salt melt ice? Sign up for three lessons free.