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
Answers
Answer:
Correct option is
A
a, b and c
a, b and c represents physical changes and d represents chemical changes.
Physical changes:
a) Hammering of a red hot iron rod to make a flat sheet.
b) Formation of ice by cooling of water.
c) Rising up of water vapors from sea to make clouds.
Chemical changes:
d) Heating of charcoal in air to high temperature till it begins to flow.
Note: During physical change there is no change in the nature of substance. However during chemical change a chemical reaction converts one substance into another with energy being either released or given out.
Answer:
27)..
a) iron is magnetized.
Magnetization of iron is a physical change and not a chemical change as there is no change of state, no change of temperature, no smell and no evolution of gas. It is because: - No Chemical process is involved. - After demagnetizing the iron it will lose its magnetic power.
28).
d) H
Since it loses an electron to become chemically stable as it has an electron and it becomes H+ ion. Since only a proton is only left behind so it is also known as a proton. Since it gains an electron to become chemically stable as it has an electron and it becomes H- ion.