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Salt is added to the ice surrounding the ice-cream ingredients because when the salt dissolves into the water the freezing point of the water lowers to below 0 C. In order for the salt to dissolve, its particles have to **dissociate** to two ions. Now the freezing point of the water has lowered. This **colligative** property, which describes the ability of a dissolved solute to lower the freezing point of its solution is also known as freezing point depression. As the ice melts it causes an endothermic reaction because the ice absorbs the heat. Once the freezing point has been lowered, the ice cream will be made because the mixture will be much colder.=====