Say you fill two plastic soft drink bottles with water, screw on caps, record their weights. Float two bottles in a bucket/pan of water and record what you see. Put one in the freezer overnight and remove the next day. Record the weights of both bottles again. Compare physical appearances. Float both in water again & record differences in way they float. What happens to water when it freees, how can this cause large rocks to crack, and relate your observations to icebergs floating the ocean & the expression “the tip of the iceberg.”