Why Do Ice Cubes Crackle?

On a nice hot summer day, an ice cold glass of water is amazing. But why does the ice crackle?

Ice doesn’t conduct heat very well, so when something — like a drink — causes it to warm up, only the outer part of the ice cube actually warms up. The inner part of the ice cube however, remains at the same temperature and doesn’t warm much at all.

When the outer part of the ice cube warms, it expands, leaving the inner part at the same size. This creates a pressure difference between the outer and inner parts of the ice, causing the inner part of the ice cube to physically crack, making the noise you hear.