Okay so in our class we did an ice cream lab where we use Ziploc bags to make ice cream. We made an ice cream mixture and then put it into a smaller Ziploc bag. Then we got a large Ziploc bag and placed ice in it and placed the bag with the ice cream mixture into the large bag and were told to put salt into the bag and then shake it until it forms ice cream?
Anyway I was wondering what caused the rapid increase in the amount of water in the bags.
salt draws out the water
first off, the ice was colder than OC. Adding salt lowers the freezing point of the "water". But it so the heat from the ice cream mixture melted some of the ice, making more salt solution in the outer bag. But melting that ice requires heat, so heat was taken from the ice salty water, making it colder, reducing temp, and causing the icecream to get colder. As long as the process goes, adding salt and cold ice, it will take heat from the ice cream mixture. Next time you do this, you need a thermometer in the ice cream mix, and a thermometer in the ice bag. You will be amazed how cold it gets as the ice melts in the salt mixtxure.
The rapid increase in the amount of water in the bags is actually a result of a scientific process called freezing point depression. When salt is added to ice, it lowers the freezing point of water. The presence of the salt causes the ice to melt at a lower temperature than it normally would, which allows it to absorb heat from the surroundings, including the ice cream mixture.
To explain further, when you shook the bag with the ice and salt, the ice melted due to the lower freezing point caused by the salt. As a result, the ice absorbs heat from the ice cream mixture, while the saltwater solution also becomes colder through the process of dissolving salt into water. This transfer of heat causes the mixture inside the smaller bag to cool down significantly.
As the ice cream mixture cools, the fats and proteins in the cream start to solidify and form ice crystals, turning it into ice cream. The shaking motion helps to evenly distribute the cold temperature and promote the formation of ice crystals throughout the mixture. Eventually, the ice cream mixture reaches a solid state, and the rapid increase in the amount of water in the bags is due to the phase change from liquid to solid as the ice cream forms.
So, in summary, the addition of salt to the ice lowers the freezing point of water, allowing it to melt. This melting ice absorbs heat from the ice cream mixture, causing it to cool down and form ice cream. The shaking helps facilitate the freezing process evenly throughout the mixture.