臺灣國際科展

表面張力測量新方法-連通管原理的再應用

科展類別
臺灣國際科展
屆次
2008年
科別
物理與太空科學
學校名稱
臺南市立後甲國民中學
指導老師
林麗華、余青展
作者
林孟妤、郭曉芮
關鍵字
表面張力 連通管原理
備註
紐西蘭正選代表: 紐西蘭2008年科技展覽會

摘要或動機

傳統表面張力的測量儀器多屬較為貴重、攜帶不便的精密儀器,不利於一般生活或教學上使用。我們發現開口不等高的連通管水面溢出低管口端時,高管口端水位比較高,於是試圖利用此液面高度差來測量表面張力。我們探討了連通管的高度、內徑大小及材質對於液面高度差的影響,並利用此原理測量已知表面張力的液體,將液面高度差所造成的壓力與標準值做比較。結果發現液面高度差確實可以用來測量表面張力,但是低管口端要用疏水性材質的細管,測量會較準確。如果使用內徑0.5mm 的鐵氟龍管,測量出來的液面高度差(h)×液體比重(ρ)的值,與標準表面張力(T)之間呈線性關係【T(dyne/cm)=10.6(h×ρ)+6.51】,相關係數高達0.9996 (p<0.0005)。本研究利用連通管的壓力原理建立了一個全新的表面張力測量裝置,我們證明了這種裝置雖然非常簡單、便宜、攜帶方便,卻可以準確的測量液體表面張力。而且它所使用的原理簡明易懂,在各級學校都可以自己製作,作為教學或實驗用。Most instruments for measuring surface tension are expensive and fragile, and therefore are seldom applicable in routine daily life or school education. We found a difference in the fluid level between two sides of a communicating pipe, of which one opening was lower than the other, when the inside liquid was just spilled out from the lower one. This study was carried out trying to evaluate the surface tension by measuring this waterhead. We studied the effects of the length, diameter and material character of the tube bound on the lower head of the communicating pipe, measuring waterhead for each respective condition. We also compared the waterhead to the surface tension of standard liquids. Results showed that the surface tension of a liquid could be evaluated by this device, and the measurement would be accurate if using a small diameter tube made by hydrophobic materials. In a case using a Teflon tube of 0.5mm in diameter, there was a linear relationship between the waterhead and the surface tension as【T(dyne/cm)=10.6(h×ρ)+6.51】, where [T] denoted the surface tension, [h] the waterhead, and [ρ] the liquid density. The correlation coefficient was r=0.9996 (p<0.0005). This study established a novel device for measuring the surface tension of liquids. The device is simple and low cost, whereas accurate and practicable, and therefore is a good tool in routine daily life or school education.


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