SPM Chemistry: Chemicals for Consumers

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Slide 1

Chemicals for consumers Enter

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Detergent Chemicals for Consumers Food Additives Soap Medicine

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Soap Soap is a salt of a compound known as a fatty acid. A soap molecule consists of a long hydrocarbon chain (composed of carbons and hydrogens) with a carboxylic acid group on one end which is ionic bonded to a metal ion, usually a sodium or potassium. The hydrocarbon end is non-polar and is soluble in non-polar substances (such as fats and oils), and the ionic end (the salt of a carboxylic acid) is soluble in water. The structure of a soap molecule is represented below:   Non-polar hydrocarbon chain ionic end. (Soluble in non-polar substances) (Soluble in water)

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Detergent Any cleansing agents that are not soap is detergent. Detergent = sodium salt of sulphonic acid Alkalis react with sulphonic acid –> detergent. Detergents are structurally similar to soaps, but differ in the water-soluble portion.

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Eg. of Common Detergents sodium alkyl sulphate  sodium alkylbenzene sulphonate

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Additives in Detergent

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Similarity and differences

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Ɔℓɛαиƨιиɢ Δcтισи Ƥяσcɛƨƨ The cleansing action process for soap and detergent is similar. Soap and detergent are surfactants. Surfactants are organic compounds that lower the surface tension of a liquid. Surfactants act as emulsifiers and foaming agents. Anion soap consists of carboxylate ion (hydrophilic = soluble in water) and long hydrocarbon tail (hydrophobic = soluble in grease /oils). Anion detergent consists of sulphate ion / sulphonate ion (hydrophilic = soluable in water) and long hydrocarbon tail (hydrophobic = soluble in grease / oils).

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Ƭнɛ αcтισи ρяσcɛƨƨ Soap or detergent is added to water. This has lower the surface tension of water and increases the wetting ability of water. Hydrophilic part of the anion dissolves in water. Hydrophobic part dissolves in grease. Scrubbing helps to pull the grease free and break the grease into small droplets. These droplets do not coagulate and redeposit on the surface of the cloth. It is because the repulsion between negative charges on the surface. The droplets are suspended in water forming an emulsion. Foam produces to float the emulsion. Rinsing helps to remove these droplets.

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Preparation of Soap by saponification Saponification – alkaline hydrolysis Soaps are prepared by hydrolyzing fats or oils under alkaline condition . Oil or Fat + Alkali Soap + Glycerol

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Preparation of Detergent Preparation of detergent is by 2 processes: Sulphonation: Petroleum fraction (long chain hydrocarbon compounds) converted into sulphonic acid with the present of concentration sulphuric acid. Water molecule is removed. Neutralisation: sulphonic acid neutralised with sodium hydroxide to form detergent (water molecule is formed).

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Tips: For those who do not know about hard water as some books neglect to explain, hard water is water with high mineral content especially calcium and magnesium ions. It affects industrial processes more than it affects human health. Non-biodegradable Effectiveness of the cleansing action and Effect to the environment

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Modern traditional

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Traditional medicine derived from natural sources such as plants and animals, without being processed chemically

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Modern medicine known as chemotherapy made in various type like pill, capsule, paste and solution

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Side effects of modern medicine

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Food Additives Food additive = a natural / synthetic substance that is added to food to prevent spoilage extend food storage life improve food appearance improve food taste improve food texture

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Preservatives Function: slow down / prevent the growth of microorganisms / bacteria / fungi extend food storage life.

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Example:

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Antioxidant Function: prevent oxidation (causes rancid fats and brown fruits) Examples:

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Flavouring Functions: improve the taste improve the smell restore taste loss due to food process Examples:

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Stabilisers Functions: prevent an emulsion from separating out Example:

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Thickeners Functions: thicken food give the food dense, smooth and uniform texture

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Dyes or Colourings Functions: add colour vanished during food processing replace colour vanished during food processing make food appear more attractive Examples:

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The end

Summary: I am from MRSM Pontian. This is a note that I made for the last chapter of form 5 in Chemistry--Chemicals for Consumers which carry 10% of my marks in Final Exam Semester One, 2012

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