You add rock salt to the ice to maintain a lower temperature.
You start with solid ice (typically at a temperature of -18 C or so) and solid salt at room temperature. When the ice begins to melt, the salt dissolves into the water. Salt water freezes at a lower temperature than water. This means that salt water can be cooled to a temperature lower than 0 C - presumably as low as the ice which is at -18 C. The lower temperature solution means your ice melts much more slowly and your ice cream freezes more quickly. If you just used plain ice without salt the ice would melt to water, the solution would remain at 0 C, which means the rest of the ice melts more quickly and your ice cream will freeze more slowly.
The ice starts at -18 C. Air and mechanically-produced heat bring some of the ice up to 0 C, whereupon it melts to liquid water. The salt then enters the water, and the solution of salt and water is cooled by the remaining ice back down below 0 C.
You can never drop the overall temperature of a substance by adding a room temperature solid to it. This should be obvious. The temperature of the solution drops because the ice is colder than the water.
Correction: You can never drop the overall temperature of a [COLDER] substance by adding a room temperature solid to it.
Adding a room temp solid to a hot liquid would drop the temperature of the liquid. I was thinking of the specific example and failed to qualify my statement properly.
Another example of reducing water temperature by adding it to another substance at the same temperature is when water is added to ammonium nitrate. Just put the two together and they get really cold. They sell plastic bags of ammonium nitrate that have weaker bags of water inside them. Pop the water bag and you have an instant cold pack.
There are other endothermic reactions out there, both chemical and physical. Other than ice and salt, you could try this one at home- vinegar and baking soda. Use a thermometer and check that both are at room temperature. Mix the two and watch the temperature drop. This is one I used to use when teaching the difference between endo- and exothermic reactions.
OK my bad - endothermic reactions must have been knocked loose from my memory bank in a tragic drinking accident. However I do maintain that ice is commonly made and stored at temps well below 0 C.
And furthermore I believe the greater part of the effect comes from exactly what I describe. The reaction may be endothermic but contributes only slightly to the overall drop in temperature of the solution.
I met someone in an adult education class who was convinced that only affluent people and wealthier ever won big in the New York State Lottery. (Or at least that it was very rare for someone not affluent.) I was stunned by that statement and never questioned her on it. I might have asked her how the air molecule-lifted balls know how to favor the independently wealthy and comfortably-incomed, and screw the poor and struggling individuals. I mean, what happens if you pick or quick-pick the same numbers as a rich player?
Clearly, the appearance of unfairness can be ascribed to presence of a certain percentage of affluent people that also participate, along with the poor folks. (Although it is absolutely terrible as “investments” go.) A certain percentage of them will go beyond the sensible option of dropping off a dollar or two for the entertainment value. In some cases they will buy plenty of tickets, many more tickets than a poor person is likely to. So even odds per ticket-entry do not imply equal odds per player.
At one time I thought that another factor is that a poor winner is far more likely to go incognito than a successfully-careered suburbanite, the latter surrounded by other affluent people. Then I read that it certainly isn’t an option for a NYS Lottery winner to do so. Sure, you can get a new name and address, and are positively encouraged to do so. But you have to be willing to share your original identity to win a grand prize.
I can remember a lottery winner from the town next to ours, was low income. Only reason I really remember him [this would have been back in 81/82ish?] was because of the gossip going around about him being broke again because he bought all of his family cars and houses and things …
My mother has a bad habit of yelling over other peoples conversations. One day, my wife told her that she needed to keep her voice down because “if everyone keeps screaming eventually the noise pollution will build up and nobody would be able to hear anything even if everyone stopped talking.”
There have been some really intriguing images from more recent Mars missions that do look superficially like trees. I’m sure they’re not trees, but it’s easy to see why people have interpreted them that way - just do a google image search on Mars Trees - the first few results are genuine NASA images, and they look kinda like trees.
Pareidolia is very likely for these people. We all do it, just some of us have the ability to determine which makes more sense: an optical illusion/misinterpretation of an object, or the trees “they” don’t want you to know about.
You’re confused here. Adding salt to water is very slightly endothermic, but nowhere near large enough to be noticeable. What happens when you add ice is that the melting point of the water is lowered. Generally speaking, the water is better at heat conduction than the ice, so whatever you are soaking in the ice/water bath will end up near the temperature of the water. With no salt, that is 0C. With salt that can go down to -40C or so. The only way to reach those low temperatures is if the ice is already that cold. Adding salt does not come close to removing enough heat:
That site gives a rough value of 4 KJ/mol of salt, or 70 J/gram of salt. The density of salt is about 2.1 g/ml, meaning one tablespoon is about 30 grams. If you add 30 grams of salt to water, you release about 2100 Joules of energy. Assume you add that to 1000 g of water, or 1 liter. The specific heat of water is 4.186 J/(g*K). So that 2100 Joules of Energy will drop it 1/2 of a degree C. In other words, not noticeable at all.
I can beat that; had a boss once who was a hard-core Baptist and believed that if you take even one drink you’re an alcoholic. Noting the Last Supper I said “so Jesus was an alcoholic?”
We kept talk to work-related stuff after that.
Others:
A co-worker who is quite sure it’s all over Dec 21 of this year. Some of us actually fear what she might do as the year wears on.
Another claimed there’s no such thing as reserve discrimination.
An atheist friend of a friend who believed that pretty much all theists - esp those nasty ol Christians - were militant fundamentalists who were just itching to twist your arm to their beliefs and were bigoted nasty people who believe God is an invisible guy who lived in the clouds (ad nauseum, the typical anti-theist gibberish). :rolleyes: I started out civil but he got more and more obnoxious/arrogant as we went along and I ended up telling him off. Happily the mutual friend is still a friend - and with the other guy too, actually, but apologized for not warning me about that aspect of his friend. And amazingly we eventually got back to being “OK” with each other overall, just didn’t get into those discussions any
My sister - well-meaning as she is - seems anxious to believe in every new age, metaphysical whatevers that come along. Too bad she wasn’t born soon enough to be a hippie in the 60s (kind of like a nicer version of the big sister in “The Wonder Years”). Her latest is stuff like homeopathy and the “evil big pharmacy” conspiracy bit and actually taking loons like Burzynski/Mercola/etc seriously.
A common belief among some of these types is that when the Bible mentions wine, it’s really talking about some non-alcoholic grape juice. Which on the face is stupid; there is good evidence that most everybody drank in antiquity, even to much younger ages than today. The reasons were more practical than alcoholic: water in most places tended to be infested with bad stuff. IIRC, daily medieval beer was much weaker than today (at least the Bud of the day), but served the purpose of being beneficial to the health while fulfilling the sex-in-canoes quotient.
Well, it would just be discrimination at that point.
Anecdotes are not data, but I remember as a (Southern Baptist) child being told that “the ‘wine’ they drank back then was so weak we’d just call it grape juice today!”
…but there are several references in the Bible to people getting drunk on wine. The wedding at Cana, for instance, where Jesus is said to have turned water into wine. The guy in charge of the party comments that the usual thing is to serve the good wine first, then bring out the cheap stuff when everyone is tipsy and doesn’t care about the taste so much - but this new stuff is better than what they’d started out with.
In a much earlier part of the book, Noah is described as getting completely and utterly smashed.
