Usually, we trust ___1___ to solve problems. Is a runny mixture too thick? Add some fluid. That’ll make it runnier. Except when the fluid makes it thicker. Scientists now think they know why.
The flow of a runny mixture, technically a suspension, is generally controlled by the size, shape and amount of the solid particles. The researchers started out with tiny hydrophilic glass beads in an organic solvent. Then they added just one percent weight of water. And like when you add water to sand and it ___2___ together, the mix turned into almost a gel. Microscopic analysis showed that a few beads stick tightly to each water drop.
Then the scientists made the glass beads hydrophobic. But ___3___. Turns out that in this case the beads form loose rings around the water droplets, as this formation minimizes each beads contact with water. The research was published in the journal Science. [Erin Koos and Norbert Willenbacher, "Capillary Forces in Suspension Rheology"—link to come]
The scientists say this effect could be used to keep solids from ___4___, or to ___5___ the viscosity of a liquid in engineering. Because sometimes, to make a mixture thicker, just add water.
【視聽版科學(xué)小組榮譽出品】
common sense clumps the addition of water still made the mixture firmer separating out of liquids fine-tune
靠常識解決問題，這是常理。流質(zhì)混合物太黏稠么？那就加點水，這樣就可以稀薄一點。不過有的時候會適得其反。科學(xué)家們貌似已經(jīng)發(fā)現(xiàn)了個中奧秘。 流質(zhì)混合物流動比較緩慢，且有一定限制，這是由其大小、形狀以及固體微粒的數(shù)量決定的?？茖W(xué)家們首先對有機溶劑中的微型親水性玻璃珠進行了實驗，先加入溶劑重量1%的水，這時候有機溶劑近似膠化，就像往沙子里灌水，微粒都凝結(jié)起來了。通過顯微鏡分析，科學(xué)家們發(fā)現(xiàn)有一部分玻璃珠和水滴緊密結(jié)合在了一起。 科學(xué)家們繼而用憎水性玻璃珠來做實驗。但是，加了水之后，有機溶劑仍然更黏稠。這就表明這項實驗中，玻璃珠在水滴周圍形成了松圈，因此玻璃珠與水的接觸也就少之又少了。這項研究結(jié)果刊登在《科學(xué)》雜志上。 科學(xué)家們表示這項發(fā)現(xiàn)可用于防止固體物析水，也可用于調(diào)節(jié)工程用液體的黏度。因為——加點水，就可以更黏稠~