水要evaporation 就要gain energy，過程中令particles kinetic energy raise
而particles kinetic energy raise，咁水的temperature 咪會升lor??
水是一個絕緣體，但點解佢都可以導電?
有關水的物理問題
2006-12-09 11:56 pm
回答 (4)
2006-12-10 12:02 am
✔ 最佳答案
食水可以導電, 不是因為食水本身, 而是當中的金屬礦物！純水本身的遵電率跟塑膠差不多.
純水只要加入苛性鹼(NaOH)之類的電解質就會導電了，那是因為電可經由電解質解離出的陰、陽離子傳導。電解質的定義→ 熔融狀態或溶於水中解離成陰、陽離子能幫助導電者，稱為電解質。 至於電解質大致可以分為兩種：1.金屬加非金屬(離子化合物) 2.酸和鹼
純水的導電率低, 兩端接電線再接上電源及燈泡, 燈泡不會亮. 完全純水的電阻率為18.3 MΩ-cm@25℃, 超純水的電阻率在17 MΩ-cm以上, 一般純水電阻率在1 MΩ-cm以上. 自來水的電阻率只有5 kΩ-cm, 導電性佳, 接近高溫時鎢的電阻率.
一般說來, 加些容易解離的酸, 鹼, 鹽, 就可以增加導電性.
導電度的產生：
自然界中的水百分百以不純物的形態組成，其濃度可能為非常稀的溶液，含有微量的可溶性物質於水中，不純物因含量少，故在水中的濃度常以"ppm"或"mg/l"來表示。部分物質如礦物質、酸、鹼類，需打斷彼此間之鍵結才能溶於水，在電流通過時，這些離子便與電流作用(即所謂的導電)，當離子數愈多，導電度愈大。超純水在理論上不應該有任何不純物，當溫度於25℃時，純水的電阻值為18.18MΩ-cm，是無法導電的。
我們一般日常生活中的水，之所以會導電，是因為水中含有許多的雜質；真正的純水是不導電的；現在常用在半導體工業中的「超純水」，去除了很多的雜質，沒有導電離子的存在，因此，幾乎是不導電的非導體！
參考: ｍｅ
2006-12-10 1:47 am
水有極微量的正，負電子，氫離子等等物質，這都是令水導電的原因!
水係唔會導電,所以唔會上升,只係水入面o既正,負電子會上升,因為係呢D野先導電呀~!
水係唔會導電,所以唔會上升,只係水入面o既正,負電子會上升,因為係呢D野先導電呀~!
參考: me
2006-12-10 12:49 am
水要evaporation 就要gain energy，過程中令particles kinetic energy raise
而particles kinetic energy raise，咁水的temperature 咪會升lor??
Particles in water have a distribution of kinetic energies (KE), some have lower energy whereas some with higher energy. Those particles near the water surface with energy high enough to escape from the attractive force between particles will be free from the surface to get into air. This is evaporation.
After the high energy particles have gone, the mean energy of the remaining particles decreases (owning to the presence of lower energy particles). Since the mean energy is a key factor to the temperature of the water, the decrease in mean energy indicates a drop in water temperature, i.e. the water cools on evaporation.
Heat from the surroundings then flows to the water because of a temperature difference. This would make some water particles to gain higher energy again. When sufficient no. of particles have acquired energy high enough to escape into the air, the process is then repeated.
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水是一個絕緣體，但點解佢都可以導電?
Pure water cannot conduct electricity. Normally, water contains minerals which contribute to the presence of metallic ions that make water to conduct electricity.
而particles kinetic energy raise，咁水的temperature 咪會升lor??
Particles in water have a distribution of kinetic energies (KE), some have lower energy whereas some with higher energy. Those particles near the water surface with energy high enough to escape from the attractive force between particles will be free from the surface to get into air. This is evaporation.
After the high energy particles have gone, the mean energy of the remaining particles decreases (owning to the presence of lower energy particles). Since the mean energy is a key factor to the temperature of the water, the decrease in mean energy indicates a drop in water temperature, i.e. the water cools on evaporation.
Heat from the surroundings then flows to the water because of a temperature difference. This would make some water particles to gain higher energy again. When sufficient no. of particles have acquired energy high enough to escape into the air, the process is then repeated.
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水是一個絕緣體，但點解佢都可以導電?
Pure water cannot conduct electricity. Normally, water contains minerals which contribute to the presence of metallic ions that make water to conduct electricity.
收錄日期: 2021-04-12 23:41:54
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