How does the freezing process of ice cream occur?
What happens to ice when salt is added?
NaCl added to ice lowers the freezing point of ice to below zero C, melting the ice takes energy, the energy must come form someplace; it comes from the water/ice mixture. The result is that the temperature of the ice/salt/water mixture is below zero. It can be MUCH lower than zero; enough to freeze the ice cream mixture.
The freezing process of ice cream occurs through a combination of two principles: lower freezing point depression and constant agitation.
To begin, ice cream mixture typically contains sugar, milk, and flavorings. When this liquid mixture is poured into an ice cream maker, the machine starts to cool it down rapidly. The machine consists of a freezing chamber surrounded by an outer chamber filled with an ice and salt mixture.
The addition of salt to the ice lowers its freezing point. Normally, pure water freezes at 0 degrees Celsius (32 degrees Fahrenheit), but by adding salt to the ice, its freezing point decreases to a temperature below 0 degrees Celsius (32 degrees Fahrenheit). This is known as freezing point depression.
As the ice and salt mixture circulates around the freezing chamber of the ice cream maker, it absorbs heat from the ice cream mixture. Heat transfer occurs because heat naturally flows from an area of higher temperature (the ice cream mixture) to an area of lower temperature (the ice and salt mixture). This heat transfer causes the ice cream mixture to cool down rapidly.
Additionally, the ice cream maker has a paddle or beater that constantly stirs the mixture while it freezes. This constant agitation prevents large ice crystals from forming and creates a smooth and creamy texture in the ice cream. By breaking up the ice crystals as they form, the paddle helps incorporate air into the mixture, giving it its characteristic light and fluffy consistency.
Overall, the combination of freezing point depression and constant agitation in an ice cream maker allows for the rapid freezing of the ice cream mixture, resulting in a delicious frozen dessert.