Ice Cubes are Cloudy on the Inside

Water contains both dissolved gases (e.g., oxygen) from the atmosphere and dissolved minerals (e.g., calcium and magnesium salts). The presence of these substances affects the temperature at which water freezes. Pure water freezes at 0~ water with dissolved gases and mineral salts freezes at a lower temperature. The higher the concentration of dissolved gases and minerals, the lower the freezing point of water. As water cools, the first layer of ice that forms is at the interface with air. As ice forms, pure water solidifies, leaving the dissolved gases and salts in solution. Thus, the freezing process concentrates the dissolved species in smaller and smaller volumes of liquid solution, effectively increasing their concentration. With a higher concentration of dissolved material, the temperature at which additional ice will form is lowered. The cloudiness in the center of an ice cube thus is the consequence of the concentration of dissolved gases and minerals that refract light and create an opaque appearance.