Answer: Anomalous Expansion of water & its effects When water is heated from 00C to 40C it contracts continously instead of expanding. Conversely expands when cooled down from 40C to 00C . This expansion of water from 40C to 00C is called anomalous expansion. When heated from 40C to 1000C its expansion is normal like the expansion of other liquids. Since water contracts when heated from 00C to 40C and expands from 40C to 1000C , its volume is smallest and the density is maximum at 40C. Hence water is heaviest at 40C.