27) Which of the following process is a physical change?
(A) Iron is magnetized
(B) Iron rusts.
(C) Red hot iron is put in steam.
(D) All of these
28) The element capable of gaining as well as losing an electron is
(A) Hg
(B) Ca
(c) Ag
(d) H
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Answers
Answer:
27. A
28. D
Explanation:
27.
Magnetization of iron is temporary and it can reversed when the magnet is removed. There is no permanent change in it. So it is a physical change.
Rusting of iron is a chemical change. Iron reacts with oxygen to form its oxide.
Red hot iron, when put in water, results in change of its crystalline structure which is irreversible. So it's a chemical change.
28.
H can lose an electron to form H+
Eg. 2 H2 + O2 = 2 H2O
in H2O, H is in H+ form.
H can gain electron to form H-
Li + H = LiH
In lithium hydride, H is in H- form.
Answer:
Required Answer :-
1. A
2. D
Know more :-
When iron is magnetised then no new substance is formed. Therefore, it is a physical change.Also, When Iron rusts then it forms a new substance which make the iron red. Now
When H gains
Li + H = LiH
Therefore
Option A
Option D