Maharashtra State Board Class 7 Science Material we use Notes / Textbook Exercises and Extra Question and Answers.
Class 7 Science Material we use Notes
- 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.
- 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).
- Replaced traditional soap, can be used in hard water.
- Made from fats or kerosene through various chemical processes.
- 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.
Fill appropriate terms in the blanks.
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