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CHEMISTRY PROJECT ON: DIFFUSION<br />

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Diffusion<br />

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Diffusion<br />Movement of molecules from an area of high concentration to an area of low concentration.<br />Movement from one side of a membrane to another, un-facilitated.<br />

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Dissolving KMnO4 crystal<br />Diffusion<br /><ul><li> Particles in a liquid or gas spread out…

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… from regions of high concentration…

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… to regions of low concentration…

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…until the particles are evenly spread out.</li></li></ul><li>Diffusion<br />

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All substances are made up of sub-microscopic particles called molecules.<br />In gases (like air) the molecules can move freely.<br />In liquids (like water) the molecules can also move.<br />In solids the molecules are more or less stationary.<br />

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Representation of molecules in a gas<br />(a)<br />(b)<br />As a result of their random movements the <br />molecules become evenly distributed.<br />

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Diffusion<br />As a result of this random movement, the<br />molecules of a gas become evenly dispersed<br />This movement is called DIFFUSION.<br />The scent of a room freshener diffuses throughout <br />a room.<br />The scent molecules diffuse from a region <br />where they are concentrated (the flower) to <br />regions where they are absent or in low concentration.<br />

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One of the ways substances enter and leave cells<br />is by diffusion.<br />If a substance is more concentrated outside a cell <br />than inside, the molecules will tend to diffuse<br />into the cell.<br />If a substance is more concentrated inside the<br />cell than outside, the molecules will tend to<br />diffuse out of the cell.<br />

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If all kinds of substance could diffuse into a cell<br />there would be a danger that poisonous <br />substances could diffuse in and kill the cell.<br />If all the substances in a cell could diffuse out<br />the cell would lose essential substances <br />(e.g. glucose) needed to keep the cell alive.<br />In fact, although the cell membrane does allow<br />some substances (e.g. oxygen and carbon <br />dioxide) to diffuse freely, it controls the exit and <br />entry of nearly all other substances.<br />

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<ul><li> Diffusion occurs because of the moving particles in gases and liquids .</li></li></ul><li>Free moving water molecules<br />Sugar molecules in sugar lump<br />Dissolving substances in water<br /><ul><li> The molecules in liquid water are constantly moving

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When water molecules bump into particles of a soluble substance, they stick to them</li></li></ul><li><ul><li> When the water molecules move away…</li></ul>… they carry particles of the solute with them<br />

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Solute<br />molecule <br />Free water molecules<br /><ul><li> Adding a solute to water reduces the amount of free water molecules</li></li></ul><li>Partially permeable membrane<br /><ul><li> Generally, small particles can pass through…</li></ul>…but large particles cannot<br />Partially-Permeable Membranes<br /><ul><li> A partially-permeable membrane will allow certain molecules to pass through it, but not others.</li></li></ul><li>Partially-permeable membrane<br />Water-solute particle is too large to pass through membrane<br />More free water molecules on this side of membrane<br />Free water molecules diffuse in this direction<br />

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THANK YOU<br />