Melting of wax is a change where a solid changes to liquid
state. Give one more such change which you observe in your
surroundings.
State whether the following statements are true or false:
(a) When a candle burns, both physical and chemical changes take place.
(b) Anaerobic bacteria digest animal waste and produce bio gas.
(c) Ships suffer a lot of damage though they are painted.
(d) Stretching of rubber band is not a physical change.
Two drops of dilute sulphuric acid were added to 1 g of copper sulphate powder and then small amount of hot water was added to dissolve it (step I). On cooling, beautiful blue coloured crystals got separated (step II). Step I and step II are:
(a) physical and chemical changes respectively.
(b) chemical and physical changes respectively.
(c) both physical change.
(d) both chemical change.
Which of the following statement is incorrect for a chemical reaction?
(a) Heat may be given out but never absorbed.
(b) Sound may be produced.
(c) A colour change may take place.
(d) A gas may be evolved.
In which one of the following countries, the ‘Earth Summit’ was held?
(a) the UK (c) Brazil
(b) Mexico (d) China
Paheli’s mother made a concentrated sugar syrup by dissolving
sugar in hot water. On cooling, crystals of sugar got separated.
This indicates a –
(a) physical change that can be reversed.
(b) chemical change that can be reversed.
(c) physical change that cannot be reversed.
(d) chemical change that cannot be reversed.
Galvanisation is a process used to prevent the rusting of which
of the following?
(a) Iron
(b) Zinc
(c) Aluminium
(d) Copper
Iron pillar near the Qutub Minar in Delhi is famous for the
following facts. Which of these facts is responsible for its long
stability?
(a) It is more than 7 metres high.
(b) It weighs about 6000 kg.
(c) It was built more than 1600 years ago.
(d) It has not rusted after such a long period.
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