Maharashtra Board Class 7 Science Solution Chapter 15 – Materials we Use
Balbharati Maharashtra Board Class 7 Science Solution Chapter 15: Materials we Use. Marathi or English Medium Students of Class 7 get here Materials we Use full Exercise Solution.
Std |
Maharashtra Class 7 |
Subject |
General Science Solution |
Chapter |
Materials we Use |
(1) (a) The substance that helps water to remove dirt from the surface of materials is called detergent.
(b) Fluride is used in toothpaste to prevent tooth decay.
(c) Soap is a salt of fatty acid and sodium hydroxide.
(d) Synthetic detergent can be used in hard water as well.
(e) For Construction purpose Portland cement is the most commonly used cement.
(2) (a) A molecule of a detergent holds on to a water molecule and oil molecule. One of end is attracted to the water and the other hold the dirts. This action remove the dirt from soiled clothes.
(b) Soaps don’t give lather with hard water. If we don’t get lather, we can say it hard water.
(c) The principle ingredients of a toothpaste, calcium carbonate and calcium hydrogen phosphate remove the dirt on teeth. Fluride helps prevent tooth decay.
(d) The ingredients of cement are silica, lime, clay sand, gravel. If cement is not used in concrete, then concrete will not be strong, leak proof.
(f) Detergents that we used in our daily life soaps – Dove, lifeboy etc
Detergent – Tide, surf-excel, sunlight etc.
(g) A delicate detergents should clean the cloths by removing all kind of strains without causing any harm the cloths.
(h) Spreading of a substance on a surface is called surface activity.
(3) (a) Difference between Natural Detergents and Man made detergents are following –
Natural Detergents | Man made detergents |
(i) Substances that are naturally available can be used as detergents | (i) Detergents that made by man for their daily life uses. |
(ii) Examples: Ritha | (ii) Soap |
(b) Difference between Soap and Synthetic detergent are following –
Soap | Synthetic detergent |
(i) Soap is sodium salt of fatly acids. | (i) Sythetic detergents are obtained from raw materials. |
(ii) Only used in soft water | (ii) Can be used in both waters. |
(c) Difference between Bath soap and Soap for washing clothes are following –
Bath soap | Soap for washing clothes |
(i) It is a type of soft soap | (i) It is a type of hard soap |
(4) (a) Soaps don’t form lather with hard water so soaps cannot be used in hard water.
(b) Oil and water in detergent is homogeneous. The one of two ends of detergent holds on water molecule and the other holds on oil molecule. It is made homogeneous.
(c) Synthetic detergents are superior to soap because sythetic detergents work can be used in both waters, hard or soft.
It is a short Answers but Some questions answers are missing so Plz don’t missed That’s question
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Wow this is very short answer this is my helpful for exam thanks
Please also give us the answer of chapter. 16 ,17,20 please