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Colloidal precipitates01:09

Colloidal precipitates

3.9K
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
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Colloids03:22

Colloids

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Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
20.2K
Colloids and Suspensions01:17

Colloids and Suspensions

2.8K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
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Precipitation Processes01:12

Precipitation Processes

3.8K
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
3.8K
Coagulation01:06

Coagulation

1.0K
Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
1.0K
Recrystallization: Solid–Solution Equilibria01:10

Recrystallization: Solid–Solution Equilibria

1.9K
Recrystallization is a purification technique used to separate impurities from solid compounds. In this technique, no chemical reactions occur. Instead, it exploits physical properties only, specifically, the solubility differences between the desired compound and impurities, either at a single temperature or at different temperatures, and under other selected conditions. The solid-solution equilibrium (solubility equilibrium) of each component in the solution represents a binary phase...
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関連する実験動画

Updated: Dec 12, 2025

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures
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Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

Published on: May 20, 2014

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コロイド系では指数関数的に速い冷却

Avinash Kumar1, John Bechhoefer2

  • 1Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada.

Nature
|August 8, 2020
PubMed
まとめ
この要約は機械生成です。

熱い物体は 寒い物体よりも早く冷却できます これは"ムペンバ効果"として知られる 逆説的な現象です この研究は,熱除去を加速させる条件を明らかにする,コロイド系におけるMpemba効果を実証している.

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Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films
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Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures
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Last Updated: Dec 12, 2025

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Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures

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科学分野:

  • 熱力学について
  • 非均衡の物理
  • コロイド科学

背景:

  • Mpemba効果は,より熱い水が冷たい水よりも速く凍るという直感に反する観察を記述しています.
  • 歴史的な観察と広範な研究にもかかわらず,Mpemba効果の根本的なメカニズムに関する一般的なコンセンサスは依然として難しい.
  • 以前の調査で様々なメカニズムが 探求されましたが 統一された説明はまだ欠けています

研究 の 目的:

  • コロイド系を用いた制御された実験環境で,ムペンバ効果を実証し,調査する.
  • Mpemba効果について最近提案された理論的枠組みを定量的に検証する.
  • 熱の除去と熱的リラックスを加速する一般的な条件を特定する.

主な方法:

  • 制御された熱冷却実験のための熱浴として水に浸されたコロイド系を用いた.
  • このコロイド系内でMpemba効果が再現された.
  • 理論的枠組みからの定量的な予測と実験結果を比較した.

主要な成果:

  • コロイド系でMpemba効果を成功裏に実証し,当初より熱いサンプルの冷却速度が速いことが示されました.
  • 実験パラメータを慎重に選択することで,典型的なシナリオよりも指数関数的に速い冷却速度を観測した.
  • 最近の理論モデルによる予測と定量的に一致する結果です.

結論:

  • Mpemba効果はコロイド系で観察され制御され,異常なリラックス現象のモデルとして用いられる.
  • この研究は,熱の除去を加速し,より速い熱平衡を達成するために必要な一般的な条件を特定しています.
  • 発見は,Mpemba効果は,重要な技術的な意味を持つより広範な異常なリラックス現象の原型であることを示唆しています.