Ans. The anomalous expansion of water refers to the unusual behavior of water when it is heated or cooled. Most substances contract when cooled and expand when heated, but water behaves differently. It contracts when cooled from room temperature to around 4 degrees Celsius, but below 4 degrees Celsius, it starts to expand again. This expansion continues until it freezes into ice. This unique property of water has important implications for various natural processes, such as the formation of ice and the circulation of water in lakes and oceans.