“I don’t really understand why water has so many properties on different scales ranging from very large and cosmic to very small quantum and quarky - Could you help by zooming in and out on water to explain what is known about it? Asks Neil Morton in Stirling. Rutherford and Fry learn about the special hydrogen bonds that makes water such an unusual liquid. Quantum physicist Professor Patricia Hunt, at the Victoria University in Wellington in New Zealand explains to Hannah the quantum properties of individual water molecules and how they link up with other water molecules in liquid water and solid ice. She describes the hydrogen bonds that give water some of it’s weird and wonderful properties such as why ice floats, why water is able to store huge amounts of heat and why water has such a strong surface tension. Science writer and author of ‘H2O – a biography of water’ Philip Ball describes how in the 18th century it was discovered that water was not one of the classical elements, but a compound liquid of water and hydrogen and explains to Adam why there are at least 15 different types of ice. Physicist Dr. Helen Czerski sets the record straight on how ice forms in oceans and lakes and why water is at its densest at 4 degrees Centigrade and not zero. Presenters: Hannah Fry & Adam Rutherford Producer: Fiona Roberts First broadcast on BBC Radio 4 in 2021.