Join in the Cambridge Science Festival excitement! This time Helen Czerski takes us to the physics department at Cambridge, known as the Cavendish laboratory. She turns the oxygen in a ballon liquid, explaining how the molecules zoom around. She shows us how to tell a real diamond from a fake diamond. Finally, she shows us a really big gun - the single stage gas gun at the Cavendish, which can fire objects at 1000s of miles per hour. She shows us how the diamond cracks when shot at with very high speed. Finally, she shows us what happens when a drop of water falls through a soap bubble.