Microwaves Shake Water
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Why Is Ice So Slow to Melt?
Water molecules in ice can’t turn, so they barely absorb the waves
View in 3DWhy is ice so slow to melt?
Remember, the waves heat food by twisting water molecules back and forth. In ice, water molecules are locked tightly to their neighbors and can’t turn. So the waves (yellow lines) pass straight through, barely weakening. That is why frozen food heated as is gets hot where it has melted while other parts stay frozen.
Why?Melted spots have molecules that can turn, so they soak up the waves and heat faster. As they heat, the ice next to them melts, and that new water soaks up waves too. So one part can boil while another is still frozen.
Learn moreBy calculation, waves travel about 12 m through ice before dropping to a third — about 700 times deeper than in water (a rough value that changes a lot with the ice’s temperature). The defrost setting switches the waves on and off, so heat from melted parts can spread into frozen parts during the pauses.
- How much deeper the waves go in ice
- about 700×
textbook formulas · example oven cavity 31.5 × 21 × 32.5 cm
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More in the series
Wavelength, standing waves and the properties of water are calculated with textbook formulas. The standing-wave pattern is a simplified sum of the metal box’s resonant modes; water’s properties come from the Debye model (water at 20 °C). In the 3D view, waves and molecules move far slower than in real life, and the water molecule is an enlarged model.