Question

Explain Why -

(a) Soap cannot be used in hard water .
(b) Oil does not mix in water . However, oil and water become homogeneous if a sufficient quantity of detergent is added .
(c) Synthetic detergents are superior to soap .
(d) Often coloured spots are formed on clothes during washing .
(e) Tobacco masheri​ should not be used for cleaning teeth.

Answer 1

a. 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.

b. 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.

c. 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.

d. 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.

e. Tobacco has various kinds of negative effects on our body. It should not be used for cleaning teeths becuase 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.