Imp Questions For All Chapters – General Science Class 7
Materials we Use
Short Questions
1. What is a detergent?
→ A detergent is a cleaning substance that removes dirt and grease from clothes, dishes, and surfaces.
2. How does soap clean dirty clothes?
→ Soap breaks down grease and dirt, allowing them to mix with water and be washed away.
3. What is the difference between soap and detergent?
→ Soap is made from natural oils and fats, while detergent is made from chemicals and works in hard water.
4. Why do we use fluoride in toothpaste?
→ Fluoride helps to strengthen teeth and prevent cavities.
5. What are the main ingredients of toothpaste?
→ Fluoride, calcium carbonate, sweeteners, and detergents help clean and protect teeth.
6. What is cement made of?
→ Cement is made from lime, silica, alumina, iron oxide, and gypsum.
7. Which type of cement is commonly used in construction?
→ Portland cement is the most commonly used cement.
8. Why is cement important?
→ Cement is used in construction to make concrete, buildings, roads, and bridges.
9. What is meant by surface activity in detergents?
→ Surface activity allows detergents to reduce surface tension, helping them remove dirt and grease.
10. Why does soap not work well in hard water?
→ Hard water contains calcium and magnesium salts, which form scum with soap, reducing its cleaning ability.
11. What are natural detergents?
→ Natural detergents come from plants, like soap nut (ritha) and shikekai.
12. What are synthetic detergents?
→ Synthetic detergents are man-made cleaning agents that work in hard and soft water.
13. What is the role of calcium carbonate in toothpaste?
→ Calcium carbonate removes plaque and cleans teeth.
14. What is the function of alumina in cement?
→ Alumina makes cement resistant to heat and gives it strength.
15. Why should we avoid tobacco masheri for cleaning teeth?
→ Tobacco masheri damages tooth enamel and can cause gum diseases.
16. What are alloys?
→ Alloys are mixtures of metals made to improve strength and durability.
17. What is meant by galvanization?
→ Galvanization is coating iron with zinc to prevent rusting.
18. What are the disadvantages of synthetic detergents?
→ Synthetic detergents cause water pollution and may harm the skin.
19. Why do we use synthetic detergents instead of soap in washing machines?
→ Synthetic detergents produce more foam and work in both hard and soft water.
20. What happens if cement is mixed with too much water?
→ If cement is mixed with too much water, it becomes weak and cracks easily.
Long Questions
1. How does detergent help in cleaning?
→ Detergents have hydrophilic (water-attracting) and hydrophobic (oil-attracting) ends, which help break down and remove dirt from clothes.
2. Why is toothpaste important for dental hygiene?
→ Toothpaste contains fluoride to prevent cavities and abrasives to remove plaque, keeping teeth strong and clean.
3. Why does soap form scum in hard water?
→ Hard water contains calcium and magnesium ions, which react with soap to form insoluble scum, making washing difficult.
4. How does cement help in construction?
→ Cement binds materials together, making strong concrete for buildings, bridges, and roads.
5. What are the harmful effects of synthetic detergents?
→ Synthetic detergents pollute water bodies, harm aquatic life, and cause skin irritation in some people.
6. Why do we need to check the expiry date of toothpaste?
→ Expired toothpaste loses its fluoride effect, making it less effective in preventing cavities.
7. Why is a separating funnel used in laboratories?
→ A separating funnel is used to separate immiscible liquids like oil and water based on their densities.
8. How can we reduce the environmental impact of detergents?
→ Using eco-friendly, biodegradable detergents and limiting detergent use can reduce water pollution.
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