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.
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