Water Freezes When Heated
By Tracy Staedter Fri
Feb 5, 2010 11:44 AM ET
Usually water freezes at 32 degrees Fahrenheit and temperatures below that. But now scientists - reporting today in the journal Science -- have found a way to keep water in a liquid form at -40 degrees F. What's more, the scientists have found another way to make the water freeze when it's heated. It's a curious phenomenon to say the least, but the results could have implications for computer climate modeling.
通常水在華氏32度或以下的氣溫結冰，但現在科學家 - 今天在科學雜誌的報告 - 已經找到一種方法在華氏負40度保持水的液態；更多的是，科學家們已發現了另一個方法，在水被加熱時使水結冰。這是一個奇怪的現象，至少可以說結果可能會影響到電腦的氣候模型。
Igor Lubomirsky and his colleagues from Israel's Weizmann Institute of Science achieved this unusual feat using dust-free water on materials called pyroelectric amorphous solids, which change their electrical charge depending on their temperature.
以色列魏茨曼科學研究所的Lubomirsky和他的同事達成這一不尋常的技藝，使用脫塵的水在稱為無定形固體的材料上，它在不同溫度情况下改變了它們的電荷。
One of the materials the scientists looked at was lithium tantalate. At 12 degrees F, the material has a negative charge. But raise the temperature to 17.6 degrees F, and it has a positive charge.
When the scientists put dust-free water on the material, the freezing point no longer was the normal 32 degrees. In fact, the freezing point depended on the charge. The scientists were able to supercool the water down -40 F without it freezing.
當科學家把脫塵的水放在那物質上，冰點不再是正常的32度；事實上，冰點取決於電荷，科學家們能夠過度冷卻水至華氏負40 度仍沒有結冰。
A negative charge did the opposite. So when they applied a negative charge to the surface, thereby raising the temperature to 17, the "heated" water froze.
負電荷卻反其道而行，因此當他們應用一負電荷的表面，提高那附近的溫度至17度，那“加熱”的水凍結。
Another strange thing happened: on a positively charged surface, the water froze from the bottom up, and on a negatively charged surface, the water froze from the top down.
另一個奇怪的事情發生：在一個正電荷的表面，水由底部向上結冰，和在一個帶負電荷的表面，水自上而下凍結。
Lubomirsky told NPR that he wasn't sure yet why any of this happened.
Lubomirsky告訴NPR說，他仍不肯定為什麼這會發生。
But the implications of the roll of dust in water should be considered in climate modeling, Franz Geiger, a physical chemist at Northwestern University in Illinois, told NPR. Ice in the atmosphere forms on dust particles and dust particles can have different electrical charges. That could influence temperatures, so it's a variable that could be taken into consideration in computer models of climate.
但是灰塵在水中打滾的影響，應在氣候模型內被考慮，在伊利諾伊州西北大學的物理化學家蓋革告訴NPR，冰於大氣層中在塵埃的微粒上形成和塵埃粒子可以有不同的電荷，這能會影響溫度，所以它是一個變物，可以在氣候變化的電腦模型加入考慮。
Photo: iStockphoto
http://news.discovery.com/tech/water-freezes-when-heated.html
在不同溫度下凍結水的電荷
A charge for freezing water at different temperatures
By Lisa Grossman
Web edition : Friday, February 5th, 2010
http://www.sciencenews.org/view/generic/id/56134/title/A_charge_for_freezing_water_at_different_
temperatures
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