Question

Q. An element reacts with Oxygen to give a compound with a high melting pont. This compound is also soluble in water. The element is likely to be --- a) calcium b) carbon c ) silicone d) iron

Q. Which of the following is a non- biodegradable substance ----a) Wood b) paper c) cotton d) plastic

Q . The commercial unit of electrical energy is ----- a) watt hour b) jule c) kilo watt per hour d) kilowatt hour

Q. What is the role of acid in our stomach ?

Note: kindly don't give answer if you aren't sure . don't copy from nat. Don't give guessing answer

Q. why does the colour of copper sulphate solution change when an iron nail is dipped in it

Answer 1

1] Calcium

2) Plastic
3)kilowatt hour
4)Acid makes the food acidic so the the enzymes can act or do better Digestion.

5)Coppor is less reactive tha iron so when iron nail is dipped in CuSO4 the reaction takes place which is displacement reaction to Fe|SO4 hence the colour changes