Why do water particles expand when frozen?
Water at 4 degree C is at it’s greatest density, below -4 C degree water expand to form crystal like (hexagonal structure) solid which take up space (expand). Equally above +4 C degree, with increasing temperature as in common with all liquids, water molecules expand. Thus ice float and deep sea maintains @ the 4 C degree at the bottom. This behavior of water is of great importance in nature to sustain life form in water (or sea). If water behave differently, say ice shrink (contract) and fall to the bottom of lake/sea, then all lakes and sea would be perminantly flozen (except your garden pond), life might not have existed.
