A phenomena is an extraordinary occurrence or circumstance, whereas chemical phenomena is defined as any natural phenomena which involves chemistry i.e. the changes to atoms and molecules. Chemical changes that occur in concrete at the microstructure level due to environmental effects are termed as thermal analysis, which is nothing but formation of chemical compounds through various chemical reactions. This article deals with various chemical changes that took place due to some chemicals or environment or conditions which may be helpful for various examinations.
1. What happens when Calcium bicarbonate is heated?
Ans. Calcium bicarbonate is heated to form calcium carbonate, water and carbon dioxide.
2. What happens when Ammonia and air passed over hot platinum?
Ans. Nitric acid and water are produced.
3. Potassium chlorate is heated to form:
Ans. Potassium chloride and oxygen are produced.
4. If a lighted paper is introduced in a jar of carbon dioxide? What happened?
Ans. The flame will be extinguished because carbon dioxide does not help in burning.
5. What happened if lime water is kept in air?
Ans. It turns milky due to carbon dioxide in the air.
What is the role of Helium in Medicines?
6. When blue litmus put in to a solution of acid what happens to it?
Ans. It turns red.
7. What happens when red litmus is put into a solution of base or alkali?
Ans. It turns blue.
8. Why does a candle blow off when covered?
Ans. Because it does not get oxygen which helps in burning.
9. Why is phosphorous kept in water?
Ans. Because with air it catches fire and in water it is insoluble.
10. Sugar gets charred on heating why?
Ans. When sugar is heated above 2000C it decomposes into carbon and water and therefore gets charred.
11. Why does the mass of an iron rod increase on rusting?
Ans. Because rust is hydrated ferric oxide which adds to its mass.
Is Nitrogen important for Human Body?
12. Why is salt mixed with ice when making ice-cream?
Ans. Salt causes reduction of temperature and helps to freeze the ice cream and freezing temperature is lowered from 00C to -50C.
13. Why does milk curdle?
Ans. Lactose or milk sugar content of milk undergoes fermentation and changes into lactic acid which on reacting with lactose forms curd.
14. Why does milk turns sour?
Ans. The microbes react with milk and grow. They turn lactose into lactic acid which is sour in taste.
15. Why does not hard water lather soap profusely?
Ans. Hard water contains sulphates and chlorides of magnesium and calcium which forms an insoluble compound with soap. Therefore soap does not lather with hard water.
16. Why does sea water boil at a higher temperature than fresh water?
Ans. Sea water contains impurities which raises the boiling point of water.
What is the function of hydrogen in the human body?
17. Why is it dangerous to have charcoal fire burning in a closed room?
Ans. When charcoal burns it produces carbon monoxide which is suffocating.
18. Why is it dangerous to sleep under trees at night?
Ans. Plants respire at night and give out carbon dioxide which reduces the oxygen content of air required for breathing.
19. Why does ENO salt effervesce on addition of water?
Ans. It contains tartaric acid and sodium bicarbonate. On adding water, carbon dioxide is produced which when released into water causes effervescence.
20. What happens when mixture of ammonium sulphate and sodium nitrate is heated?
Ans. Ammonium nitrate is formed which on decomposition gives nitrous oxide.
From the above article we come to know about various chemical reactions which makes changes like how milk becomes sour, Why iron rust etc.