Ice cream and freezing point depression
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- เผยแพร่เมื่อ 13 ก.ค. 2017
- From our free online course, “Science & Cooking: From Haute Cuisine to Soft Matter Science (physics)”: www.edx.org/course/science-co...
Dan Souza discusses how to make a smooth and delicious vanilla ice cream, and Harvard Professor Michael Brenner explains the science behind it.
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Hi there, just wondering if you know whats the anti freezing power of palm sugars, is it the same as table sugar?? i cant seem to find any information online
But why does the liquid solute + solvent have higher entropy than just the liquid solvent?
This is not very easy to understand without a visual, but here goes(I know I am a year late, but this is for those who are still curious): picture that you have a beaker of H2O.. as you may know, its freezing point is 0 deg. Celsius. So, this process is near spontaneous, and it will form a solid lattice with no problem. However, now let us imagine a scenario where we add a solute, say NaCl. Now that we have added NaCl into our beaker, we observe its freezing point. It seems that the freezing point has now been lowered.. funny. From a molecular standpoint, inside the beaker: some NaCl molecules have actually blocked the phase change of H2O from liquid to solid. Picture the molecules in motion, and every now and then, an NaCl molecule will “block” an H2O molecule from bonding to the “solid lattice”. Effectively, this is because there are molecules in the solution that are not freezing. So, being the jerks that they are, their fat arses block the guys who are actually trying to freeze up. Given that there are MORE molecules, and MORE interactions(collisions), there is a higher disorder in the “system”. This is vaguely known as entropy. Entropy has therefore increased, lowering the amount of H2O molecules that have phase-changed, and lowering the freezing point. Compared to the plain H2O beaker, the entropy will be higher in the solution.
as a solute is mixed in the solvent , solute particles are evenly distributed in solvent, but due to that we can't predict , which particles is present at a particular place this indicates that due to adding solute there is a little uncertainty added in solution, and entropy is not just randomness , it also indicates uncertainty within the system , so entropy increases
So I understand how salt lowers the "freezing point' of the water and has an impact on what happens inside the canister, but I still can't understand how the salt actually lowers the "temperature" of the ice/water mixture in the bucket. How does salt make the ice colder?
It doesn’t. If your freezer is set at -10C, that is the temperature of your ice you started with. Heat only flows from hot to cold. Your ice is the coldest object in ice cream making process so it only absorbs heat energy; therefore, it cant get any colder than what you started with.
I didn't get it either. Tell me when you figure it out
@@fatimaasad2005 As user dn7 mentioned, the ice is much colder than you need. The problem is that ice by itself is bad at absorbing heat from your churning vessel, because it's shape and tendency to melt prevent it from making constant comprehensive contact with the vessel. That's where the water comes in. If you make an ice water bath for your churning vessel, the ice can cool the water, and the water can make contact with every surface of the vessel. The catch is that you need the contents of the vessel to get below freezing, but the water can't do that because the water in an ice water bath never goes below freezing. No matter how cold your ice is, it can't make the water go below freezing. But, if you add salt to the ice water, it lowers the freezing point to several degrees below freezing. This allows your very cold ice to cool the water to several degrees below freezing. It can now freeze the contents of the churning vessel because it's below freezing. Hope this helps!!
Well, the salt doesn't actually lower the 'temperature' of ice , it lowers the "Freezing point" of the solution -means the solution will remain in liquid phase even below 0°C(freezing point of water) and that happens, because in a solution ,the salt particles are evenly distributed and thus the solvent particles(water for eg.) have come slightly apart as the salt particles have occupied the space , so when freezing pure water we just remove heat enough to bring 2 water molecules(which are comparatively closer) together to form solid , but in our case they have gone slightly apart, so we can say they have gained a bit more energy than previous case , so we also need to remove that extra energy-extra heat to bring the particles together to form solid, and by removing heat, temperature is lowered, and THEN, freezing point is achieved .
Dang it’s Dan from American test kitchen. 😂
why he kinda cute
there is no water in the mixture cream,milk, eggs
There is water in the mixture; whole cow's milk contains about 87% water, chicken egg about 74%, etc. ( 8675309 ) ;)
no recipe and instructions this video is not valid
Get recipe at ATK / COOKS Country by joining site ( copyright issue ); that's why Michael Brenner explains the science and talks over the recipe.