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Materials We Use, Q1] Fill in the blanks., (a), (b), (c), (d), (e), , The substance that helps water to remove dirt from the surface of materials is called detergent., Fluoride is used in toothpaste to prevent tooth decay., Soap is a salt of fatty acid and sodium hydroxide., Synthetic detergents can be used in hard water as well., For construction purposes Portland cement is the most commonly used cement., , Q2] Answer the Following., •, , How does the use of a detergent help to clean soiled clothes ?, , Ans. Detergent is a cleansing agent that combines with the impurities to make them more soluble and, therefore wipe them away. A molecule of detergent consists of two ends. One of its ends is attracted, towards the water while the other holds on to the dirt. This results in the mixing of dirt and water. Due, to the ability to get attached to both oil and water, detergent molecule spreads easily. This property of a, substance expanding on a surface is known as surface activity and the substance is known as surfactant., One of the effects of surface activity is lather formation. This action of detergent molecule results in the, removal of dirt and stains from the clothes., •, , How will you check with the help of soap powder whether water is hard ?, , Ans. Soap can be used to check wether sample of water is hard or soft. Soaps do not give lather with, hard water instead form scum whereas they give lather with soft water. If we do not get lather in water, while using soap, we can say it is hard water., •, , What are the important ingredients of a toothpaste , and what is the function of each ?, , Ans. The important ingredients of a toothpaste are abrasives, water and fluoride. Abrasives such as, calcium carbonate and calcium hydrogen phosphates help to remove the dirt on teeth and also helps to, polish them. Fluoride is the most common active ingredients used to prevent decay of our teeth. It helps, in strengthening of bones and the enamel which covers the teeth., •, , What are the ingredients of cements ?, , Ans. The ingredients of cement are lime (CaO), clay, silica along with some other oxides of aluminium,, iron and magnesium. Gypsum (CaSO4, 2H2O) is usually added to regulate the setting rate of cement., •, , What will happen if cement is not used in making concrete ?, , Ans. Concrete is a mixture of cement, water, sand and gravel. Cement helps in making the structures, strong and leak proof. If cement is not mixed in concrete, the structures made using concrete will not be, strong and leak-proof and thus will have the chances of falling down., •, , Make a list of detergents that you use.
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Ans. The detergents which we use in our daily lives are:-, , •, , o Ritha and shikhakai for washing hair, o Soaps like dettol, dove, lifeboy etc. for bathing, o Detergents like surf excel, tide etc. for washing clothes, What should be expected from a detergent for delicate garments ?, , Ans. A delicate detergent should clean the clothes effectively without affecting the quality of the, clothes. It should have the ability to remove all kinds of stains without causing any harm to the clothes., •, , What is meant by ‘ surface activity’? Name three chemicals responsible for the surface activity, of various detergents., , Ans. Surface activity of a substance is the property by virtue of which it can spread on a surface. For, example, soap water easily spreads on the any kind of surface and thus is used for cleaning purpose., Chemicals responsible for the surface activity of various detergents are alkylbenzene sulphonate,, alcohol ethoxysulphates and alkyl sulphates., Q3] Write Difference and Similarities of:•, , Natural Detergent & Man-made detergent
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•, , Soap & Synthetic Detergent, , •, , Bath Soap & Soap for Washing Clothes.
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•, , Modern Sement & Ancient Sement., , Q4] Explain Why?, •, , Soap cannot be used in hard water., , Ans. Soaps cannot be used in hard water because they lose their cleansing property when used with it., Soaps do not form lather with hard water and instead forms scum, as a result of which it loses its, cleansing property., •, , Oil does not mix in water . However, oil and water become homogeneous if a sufficient quantity, of detergent is added., , Ans. Oil and water are two immiscible liquids which means both of them repel each other. But when we, add a detegent to a solution conatining water and oil, the mixture becomes homogeneuos. This happens, because of the detergent molecule. The detergent molecules have two ends. One of its end holds on to, a water molecule and the other end holds on to the oil molecule. These opposing forces helps in, dissolving the oil in water and thus making a homogeneous mixture.
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•, , Synthetic detergents are superior to soap., , Ans. Synthetic detergents are superior to soap because synthetic detergents work both in soft water and, hard water. In contrast, soaps work only in soft water and they are not effective in hard water., •, , Often coloured spots are formed on clothes during washing., , Ans. The laundry, skin care, beauty and personal hygiene products which we use commonly can cause, stains and color changes in our clothes. Toothpaste, perspiration, facial soap, deodorants, hair sprays,, strong perfumes with alcohol and even rain are often the cause of stains on garments. All these stains, may eventually dry up not causing any visible stain however, age and exposure to heat will cause them, to reappear., •, , Tobacco masheri should not be used for cleaning teeth., , Ans. Tobacco has various kinds of negative effects on our body. It should not be used for cleaning teeths, because it can harm th soft and hard tissues of our mouth. Use of tobacco poses serious risks like oral, cancer, gum disease, poor healing after surgery, receding gums, and tooth decay., , -Yash Wani, 7’A
