7.15 MHCERT 7th General Science 15.Matarials We Use

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MHCERT General Science 7th Materials We Use



1. Fill appropriate terms in the blanks. (white cement, soap, detergent, wearing of bones, tooth decay, hard, soft, Portland, fatty acid)


3.


4.


Pro


(a) The substance that helps water to remove dirt from the surface of materials is called


(b) Fluoride is used in toothpaste to prevent


(c) Soap is a salt of sodium hydroxide.


and


(d) Synthetic detergents can be used in water as well.


(e) For construction purposes cement is the most commonly used cement.


2. Write answers questions. to the following


(a) How does the use of a detergent


help to clean soiled clothes? (b) How will you check with the help of soap powder whether water is hard?


(c) What are the important ingredients.


of a toothpaste, and what is the


function of each?


(d) What are the ingredients of cement?


(e) What will happen if cement is not


used in making concrete?


(f) Make a list of detergents that you


use.


(g) What should be expected from a detergent for delicate garments? (h) What is meant by 'surface activity'? Name three chemicals responsible for the surface activity of various detergents.


3. What are the differences between similarities


and


(a) Natural detergents and man-made detergents


(b) Soap and synthetic detergent (c) Bath soap and soap for washing clothes


(d) Modern cement and ancient cement


4. 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.

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