M.I.C.C. Manchester Ice Cloud Chamber Site and content created using Xara Designer Pro 6 Droplet Freezing This project investigates the temperature at which droplets freeze after being doped with various types of ice nuclei.  Ice nuclei are prevalent throughout the atmosphere and determine the temperature at which supercooled liquid water droplets (colder than 0°C but not frozen) actually freeze to form ice.  The temperature at which frozen precipitation forms in the atmosphere can greatly influence cloud conditions and the weather. Droplets of water containing a range of different substances in solution (e.g. ash, soot, organic material etc.) are placed on a metal surface with a high thermal conductivity.  This is then placed into a freezer and begins to cool.  The droplets freeze one by one once a certain temperature below zero has been reached, and this temperature is dependent on what substance is in the water.  The freezing-temperature range for different substances can be found (Fig. 1).  In addition, it’s possible to determine how long it takes for a droplet to freeze when it is held at a constant temperature; heterogeneous freezing is probabilistic, and the average time taken to freeze can be determined.  (Heterogeneous freezing involves the encouragement of liquid water to freeze when at a temperature between 0–-36°C; water colder than about -36°C will freeze automatically and this is known as homogeneous freezing.  More details are available in the Formation of Ice Crystals section, in particular, Fig. 1 in that section.) . Fig. 1. Droplets of deionised liquid water doped with various substances on a cooling metal surface solidify into ice as the temperature decreases.  Ice nuclei within the droplet acts as a seed for heterogeneous freezing. The crystallisation wave front can be seen propagating through the liquid after nucleation.  Change video resolution by starting video and choosing from bottom right of player. Choose resolution