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States of Matter and Separation - Emulsions and Suspensions

Grade 9IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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A suspension is a heterogeneous mixture containing large solid particles (typically >1000 nm> 1000\text{ nm}) that are sufficiently large for sedimentation. If left undisturbed, the particles will eventually settle at the bottom due to gravity.

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An emulsion is a specific type of colloid formed by dispersing one liquid into another immiscible liquid (e.g., oil in water or water in oil).

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Emulsifying agents (or emulsifiers) are substances that stabilize an emulsion. They contain both a hydrophilichydrophilic (water-loving) head and a hydrophobichydrophobic (water-fearing) tail, preventing the dispersed droplets from coalescing.

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The Tyndall Effect is the scattering of visible light by colloidal or suspended particles. A beam of light becomes visible when passed through a suspension or emulsion, whereas it remains invisible in a true solution.

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Separation of a suspension is commonly achieved via filtration because the particles are larger than the pores of the filter paper. Emulsions are often separated using a separating funnel (based on density) or centrifugation.

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The stability of these mixtures can be influenced by temperature and the concentration of the dispersed phase.

📐Formulae

Concentration (v/v %)=Vdispersed phaseVtotal solution×100%\text{Concentration (v/v \%)} = \frac{V_{\text{dispersed phase}}}{V_{\text{total solution}}} \times 100\%

Concentration (m/m %)=msolutemtotal mixture×100%\text{Concentration (m/m \%)} = \frac{m_{\text{solute}}}{m_{\text{total mixture}}} \times 100\%

ρ=mV\rho = \frac{m}{V}

💡Examples

Problem 1:

A student prepares an emulsion by mixing 15 mL15\text{ mL} of olive oil with 135 mL135\text{ mL} of water and an emulsifier. Calculate the volume percentage (v/v %) of the oil in the resulting emulsion.

Solution:

Total Volume=15 mL+135 mL=150 mL\text{Total Volume} = 15\text{ mL} + 135\text{ mL} = 150\text{ mL} v/v %=15150×100\text{v/v \%} = \frac{15}{150} \times 100 v/v %=10%\text{v/v \%} = 10\%

Explanation:

To find the percentage, divide the volume of the dispersed liquid (oil) by the total volume of the mixture and multiply by 100.

Problem 2:

Compare the behavior of a 1 M1\text{ M} NaClNaCl solution and a muddy water suspension when a laser pointer is directed through them. Which one exhibits the Tyndall Effect?

Solution:

The muddy water suspension will exhibit the Tyndall Effect, while the NaClNaCl solution will not.

Explanation:

In a true solution like NaClNaCl in water, the particles (Na+Na^{+} and Cl−Cl^{-} ions) are too small (usually <1 nm< 1\text{ nm}) to scatter light. In muddy water, the suspended soil particles are large enough to reflect and scatter the light beam, making the path of the laser visible.

Problem 3:

A mixture has a total mass of 250 g250\text{ g}. After filtration and drying, 12.5 g12.5\text{ g} of solid residue is recovered from the filter paper. Calculate the mass percentage of the suspended solid.

Solution:

Mass %=12.5250×100\text{Mass \%} = \frac{12.5}{250} \times 100 Mass %=5%\text{Mass \%} = 5\%

Explanation:

The mass percentage is calculated by taking the mass of the recovered solid (the suspended phase) and dividing it by the initial mass of the total mixture.