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Why do we salt the ice when making ice cream?

timothyrice.org

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Re: Why do we salt the ice when making ice cream?

#91

Post by dlgeek »

Maursault wrote: post #86
dcow wrote: post #62

Earlier quoted context omitted.

I understand Fahrenheit now.

I thought I did, but just thinking about what temperature is, i.e. the degree of hotness or coldness something is, so it relates to heat, which is the energy transferred from something hot to something cold, so it relates to energy, the more energy something has the hotter it is, the less energy the colder. So I am utterly confused now why wind cools or even can be cold, and wind chill should be a contradiction, and…

The air around you is (usually) colder than your body. That means your body is transferring energy to the air. When the wind blows, convection causes you to transfer more energy to the air than you do when the wind doesn't blow. That increased transfer of heat away from you makes the wind seem colder/creates wind chill.

Re: Why do we salt the ice when making ice cream?

#92

Post by kgwgk »

eyelidlessness wrote: post #74
topaz0 wrote: post #70

Earlier quoted context omitted.

"then it won't be ice anymore". Not so: the freezing point is the temperature at which ice and water are in equilibrium. If you take a bowl of ice to its freezing point it will still be entirely frozen. Then if you continue adding energy, it will remain at its freezing point while progressively more of it melts, i.e. going from 100% ice to 50% ice/50% water to 100% water. All at one temperature. In other words, if yo…

> and none of it goes to increasing the temperature You’re clearly more knowledgeable than I am, but this strikes me as probably wrong? The temperature at the surface has raised, which is how some of the surface ice melted. The temperature on average has to raise because thermodynamics. If I understand the article, the core temperature of the remaining ice can decrease and localities can decrease with them. But the e…

>> If you take a bowl of ice to its freezing point it will still be entirely frozen. Then if you continue adding energy, it will remain at its freezing point while progressively more of it melts [...] if you are at the freezing point, then all of the energy you add goes to melting the ice (and none of it goes to increasing the temperature), until all of the ice is gone.

> this strikes me as probably wrong? The temperature at the surface has raised, which is how some of the surface ice melted. The temperature on average has to raise because thermodynamics.

What do yo you think is wrong in the quoted passage?

The "temperature on average" of the system described is the temperature of every part of it: the temperature where the liquid and solid phases co-exist. When you heat that system (i.e. add energy) the temperature doesn't have to increase "because of thermodynamics". The ice melts and everything remains at the same temperature. Only when the ice is gone the water starts to warm up.

Re: Why do we salt the ice when making ice cream?

#93

Post by topaz0 »

ekanes wrote: post #83
topaz0 wrote: post #70

Earlier quoted context omitted.

"then it won't be ice anymore". Not so: the freezing point is the temperature at which ice and water are in equilibrium. If you take a bowl of ice to its freezing point it will still be entirely frozen. Then if you continue adding energy, it will remain at its freezing point while progressively more of it melts, i.e. going from 100% ice to 50% ice/50% water to 100% water. All at one temperature. In other words, if yo…

Right on. It’s the same for boiling, isn’t it? The water “can’t” get above 100 degrees C - added energy just goes into making steam. Right?

That's right (well... assuming constant pressure lower than the critical pressure.)

Re: Why do we salt the ice when making ice cream?

#94

Post by topaz0 »

eyelidlessness wrote: post #81
lupire wrote: post #80

Earlier quoted context omitted.

At melting, the energy is going into the state change.

And the state change occurs when the portion of solid ice becoming liquid water warms however slightly, even if there’s a cooling side effect on the remaining ice as more energy is dissipated during that warming. Or am I still misunderstanding?

Yes. It is literally an isotherm. Energy is added without changing the temperature.

Re: Why do we salt the ice when making ice cream?

#95

Post by HPsquared »

mensetmanusman wrote: post #63
CliffStoll wrote: post #39

Now check out Eutectic mixtures ... old-timers may remember soldering with 63-37 tin/lead solder. The reason? With any other mixture of lead/tin, the liquid solder freezes over a temperature range, often resulting in what very-old-timers called a "cold solder joint". For example, 50-50 tin/lead mixture starts melting at 183C and is fully melted at 214C. Using Eutectic Solder, the phase transition happens at exacctly…

Without lead you get tin whiskers. I wonder how the math works out in terms of what’s better for the environment if electronics break a lot more often…

Given the explanation above, this now makes a lot more sense: if the (non-eutectic) solder has cooled gradually, some the higher melting component will freeze first at the coolest location, and things will move around, leaving less of the "low-melting" components in the remaining molten solder. Once it's all solidified, some areas will have more tin and other areas will have more of the other elements. This will induce some weirdness, maybe the tin will want to diffuse to other parts where there is less (is this possible?) or maybe just there will be areas of relatively pure tin, perhaps more susceptible to whisker formation?

On the other hand an evenly-frozen mix of lead and tin (eutectic) wouldn't have these non-uniformities as there would be no driving force for it. One location freezing before the other wouldn't change the composition of the remaining melted solder.

Re: Why do we salt the ice when making ice cream?

#96

Post by shultays »

We add some salt to most deserts as well, to make them more tasty (I am no expert so I don't actually know how it makes them "more tasty"). I highly doubt the salt in ice cream is for melting point, and probably it is also for taste reasons. OP is probably overthinking this

Re: Why do we salt the ice when making ice cream?

#97

Post by ohwaitnvm »

shultays wrote: post #96

We add some salt to most deserts as well, to make them more tasty (I am no expert so I don't actually know how it makes them "more tasty"). I highly doubt the salt in ice cream is for melting point, and probably it is also for taste reasons. OP is probably overthinking this

You don't add the salt to the ice cream, you add it to the ice that surrounds the ice cream-making container.

Re: Why do we salt the ice when making ice cream?

#99

Post by gjs278 »

shultays wrote: post #96

We add some salt to most deserts as well, to make them more tasty (I am no expert so I don't actually know how it makes them "more tasty"). I highly doubt the salt in ice cream is for melting point, and probably it is also for taste reasons. OP is probably overthinking this

No post body was provided.

Re: Why do we salt the ice when making ice cream?

#100

Post by shultays »

ohwaitnvm wrote: post #97
shultays wrote: post #96

We add some salt to most deserts as well, to make them more tasty (I am no expert so I don't actually know how it makes them "more tasty"). I highly doubt the salt in ice cream is for melting point, and probably it is also for taste reasons. OP is probably overthinking this

You don't add the salt to the ice cream, you add it to the ice that surrounds the ice cream-making container.

Aha, sorry I should give it a proper read. Didn't notice it was talking about the ice

Also in the recipes I googled right now, salt is also an ingredient for icecream

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