时差N小时 你见过老式冰淇淋机吗?(下)(在线收听) |
The coldest that salt less ice water can get is 32 degrees Fahrenheit, where there's a balance between the rates of melting and freezing. 含有少量盐的冰水温度最低可达华氏32度,这一温度是凝固和融化的平衡点。 Add salt to the mix and the energy balance tips, allowing the temperature to drop below 32 without freezing. 将盐加到最大量能打破能量平衡,使得温度低于32度而不结冰。 Let's say you toss a handful of salt into ice water, and the temperature drops to 20 degrees. 让我们尝试一下,你将少量盐投放到冰水里,温度降到了20度。 At this lower temperature, salty ice water can absorb more heat from the mixture inside the canister, freezing it faster than salt less ice water could. 在这种低温里,盐水能从金属罐里的混合物中吸收更多的热量,与淡冰水相比能尽快将其冻结。 This means you can quit cranking sooner, kick back on the porch and enjoy some good-old-fashioned ice cream. 这意味着你能快速停止摇动,返回走廊,享受美味的老式冰淇淋了。 |
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