Which of these is an irreversible change?
a) Stretching of rubber band
b) Melting of ice
c) Burning of paper
d) Dissolving salt in water
Answer: c) Burning of paper
The phase changes of the moon are an example of:
a) Fast change
b) Periodic change
c) Chemical change
d) Irreversible change
Answer: b) Periodic change
Which of these is NOT a physical change?
a) Tearing of paper
b) Mixing of salt with water
c) Burning of wood
d) Sublimation of ammonium chloride
Answer: c) Burning of wood
To prevent rusting of iron, we can:
a) Expose it to more air
b) Apply coats of zinc or paint
c) Keep it in water
d) Heat it regularly
Answer: b) Apply coats of zinc or paint
The conversion of milk into curd is:
a) A physical change
b) A reversible change
c) A chemical change
d) A periodic change
Answer: c) A chemical change
When chalk breaks into pieces, it is an example of:
a) Chemical change
b) Physical change
c) Both chemical and physical change
d) Neither chemical nor physical change
Answer: b) Physical change
In a chemical change:
a) Only physical properties change
b) The characteristics of reactants and products are same
c) New products are formed
d) All changes are reversible
Answer: c) New products are formed
The process of digestion is:
a) A physical change
b) A chemical change
c) Neither physical nor chemical
d) Both physical and chemical
Answer: b) A chemical change
When water is poured on limestone:
a) Heat is absorbed
b) Heat is released
c) No heat exchange occurs
d) First heat is absorbed then released
Answer: b) Heat is released
To protect foodgrains from insects, we can use:
a) More water
b) Insecticide tablets wrapped in cloth
c) Direct sunlight
d) Cold storage only
Answer: b) Insecticide tablets wrapped in cloth
The formation of vapor from water is:
a) Chemical change
b) Irreversible change
c) Physical change
d) Permanent change
Answer: c) Physical change
Which of these changes cannot be reversed?
a) Stretching of rubber band
b) Melting of wax
c) Growth of plant from seed
d) Formation of ice from water
Answer: c) Growth of plant from seed
