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Maharashtra State Board Class 7 Science Material we use

Maharashtra State Board Class 7 Science Material we use Notes / Textbook Exercises and Extra Question and Answers.

Class 7 Science Material we use Notes

 

Toothpaste:

  • Principal ingredients: Calcium carbonate, calcium hydrogen phosphate.
  • Functions: Remove dirt and polish teeth.
  • Contains fluoride to prevent tooth decay and strengthen bones and tooth enamel.

 

Detergents:

  • Detergent defined as “a substance that cleans or wipes away dirt.”
  • Examples of natural detergents: Soap nut (ritha) and soap pod (shikekai) containing saponin.
  • Man-made detergent: Soap invented about 2000 years ago, traditionally made from animal fat and wood ash.
  • Types of soaps: Hard soap for washing clothes (sodium salt of fatty acids), soft soap for bathing (potassium salt of fatty acids).
  • Soap doesn’t work well in hard water (forms scum).

 

Synthetic Detergents:

  • Replaced traditional soap, can be used in hard water.
  • Made from fats or kerosene through various chemical processes.

 

Cement Production:

  • Cement is vital in construction, used to make concrete materials.
  • Composition of Portland cement: 60% lime (calcium oxide), 25% silica (silicon dioxide), 5% alumina, iron oxide, and gypsum.
  • Named after the Isle of Portland in England.
  • Historical use of cement dates back to ancient Romans, lost knowledge revived by John Smeaton in 1756.
  • Concrete is prepared by mixing cement, water, sand, and gravel for various construction applications.

 

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