Question

Long answer type questions
21) Compare fertilizer and Manure.
22) Explain at least any 3 chemical methods of food preservation.
23) (a)What are petrochemicals?
(b) Why we should avoid wearing synthetic clothes while working in kitchen or in a
laboratory?
24) What are consequences of swallowing plastics by animals?
25) Compare physical properties of metals and non metals.

plz anwer these questions of class8th sst andbi will mark as brainlist​

Answer 1

Answer:

21. Manures are obtained from natural sources, whereas fertilisers are synthetically manufactured in the factories. Manures are eco-friendly, whereas fertilisers harm the useful microbes present in the soil and also decrease the soil fertility if used for a longer time.

22. There are several traditional methods of food preservation used at the household level that can be classed as chemical methods. Substances such a sugar, salt, vinegar, spices and wood-smoke are generally regarded as safe and natural preservatives. Salting, sugaring and smoking are all methods of curing foods.

23. a There are several traditional methods of food preservation used at the household level that can be classed as chemical methods. Substances such a sugar, salt, vinegar, spices and wood-smoke are generally regarded as safe and natural preservatives. Salting, sugaring and smoking are all methods of curing foods.

23. b Synthetic fibres melt on heating. If they catch fire, they melt and stick to the body of the person wearing them. This is why it is advised not to wear clothes made of synthetic fibre while working in a kitchen or in a fire laboratory.

24. Swallowed plastic fills the stomach and not surprisingly this reduces the feeling of hunger. Animals eat less, obtain less energy, and weaken. Larger pieces of plastic can also block their gastrointestinal tract so that the plastic can no longer be excreted.

25. They have high electronegativities. Nonmetals are insulators which means that they're poor conductors of electricity. They are dull, they do not have lustre like metals. Nonmetals are poor conductors of heat.