Instant Ice in 6 Steps

Watch a bottle of water skip freezing, then turn to ice the instant you bump it.

 

Materials you'll need

• Bottle of water
• Bottle of plain tap water (same size)
• Permanent marker
• Freezer
• Glass and spoon, for serving

 

Step-by-step tutorial

Step 1: Fill one bottle with bottled or filtered drinking water and a second, same-size bottle with plain tap water. Label the tap water bottle "TAP" with a permanent marker so the two don't get mixed up.

Step 2: Lay both bottles flat in the freezer, side by side.

Step 3: Set a timer for about 2 hours, then leave the freezer completely alone — no opening the door, bumping, or shaking.

Step 4: Check the tap water bottle first. Once it's frozen solid all the way through, that's your cue: the drinking water bottle should still look and feel completely liquid, even though it's colder than the normal freezing point.

Step 5: Very gently lift the drinking water bottle out of the freezer, being careful not to shake, squeeze, or bump it, and set it down on a table or counter.

Step 6: With an adult's help, give the bottle one strong, sudden bump against a hard surface. Watch ice race through the water in seconds, then scoop the soft, slushy ice into a glass and enjoy.

Learn more

This works thanks to a strange state called supercooling — water can drop below its normal freezing point (32°F/0°C) and still stay liquid, as long as nothing gives ice crystals a place to start growing. That starting point is called a nucleation site, like a speck of dust or a dissolved mineral. Bottled or filtered drinking water has very few of these specks, so it can supercool in the freezer without turning solid, while the minerals in tap water give ice plenty of places to start, so it freezes right on schedule. When you bump the supercooled bottle, the jolt lines up a few water molecules into the first tiny ice crystal, and the rest of the bottle freezes into slushy ice around it almost instantly.

Still thinking about that instant ice? Science of Cooking: Ice Cream lets kids control ice crystal formation on purpose, turning the same freezing science into a treat they mix and eat.