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Water

Water as a solvent — solutions, solubility and crystals — and how water reacts with metals and why it can be hard or soft.

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What this chapter covers

  1. Solutions

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    • Water as a SolventWater dissolves substances into aqueous solutions.
    • Components of SolutionsSolute dissolves in a solvent.
    • Types of Solutions by ConcentrationDilute or concentrated, by solute amount.

  2. True Solution, Colloids and Suspension

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    • True SolutionClear, homogeneous; particles never settle.
    • Colloid SolutionTranslucent, between solution and suspension.
    • Suspension SolutionOpaque; particles settle if undisturbed.

  3. Solubility

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    • Solubility Definition and FactorsGrams dissolving in 100 g solvent.
    • Types of Solutions by SolubilityUnsaturated or saturated at that temperature.

  4. Water of Crystallisation

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    • CrystalsDefinite geometric shape; orderly atoms.
    • Hydrated and Anhydrous SaltsHeating removes water; adding restores colour.

  5. Efflorescence, Deliquescence and Hygroscopy

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    • EfflorescenceLoses crystal water to air, powders.
    • DeliquescenceAbsorbs moisture and dissolves in it.
    • HygroscopyAbsorbs moisture without dissolving; drying agents.

  6. Reaction of Metals with Water

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    • Reactivity and WaterOnly metals above hydrogen displace it.
    • Reaction with Cold WaterPotassium and sodium react very vigorously.
    • Reaction with SteamMg, Al, Zn, Fe form oxides.

  7. Hard Water and Soft Water

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    • Definitions and Reasons for HardnessCalcium, magnesium salts stop lathering.
    • Types of Hard WaterTemporary removed by boiling; permanent not.
    • Softening of Hard WaterRemoving calcium and magnesium ions.
    • Advantages of Hard WaterHealthy teeth, bones; checks lead poisoning.
    • Disadvantages of Hard WaterWastes soap, fuel; scale, corrosion.

Try a sample question

Which softening method works on both temporary and permanent hardness of water?

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