Class 7 Science

1. Which of the following is a physical change?
(a) Rusting of iron
(b) Combustion of magnesium ribbon
(c) Burning of candle
(d) Melting of wax
2. 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.
3. Which of the following is a chemical change?
(a) Twinkling of stars
(b) Cooking of vegetables
(c) Cutting of fruits
(d) Boiling of water
4. 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.
5. A chemical change may involve –
(a) change in colour only
(b) change in temperature only
(c) evolution of gas only
(d) any or all of the above
6. Galvanisation is a process used to prevent the rusting of which of the following?
(a) Iron
(b) Zinc
(c) Aluminium
(d) Copper
7. Which of the following is/are true when milk changes into curd?
(i) Its state is changed from liquid to semi solid.
(ii) It changes colour.
(iii) It changes taste.
(iv) The change cannot be reversed.
Choose the correct option from below:
(a) (i) and (ii) are correct
(b) (ii) and (iii) are correct
(c) (i), (iii) and (iv) are correct
(d) (i) to (iv) are correct
8. 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.
9. A man painted his main gate made up of iron, to
(i) prevent it from rusting. (ii) protect it from sun. (iii) make it look beautiful. (iv) make it dust free.
Which of the above statement(s) is/are correct?
(a) (i) and (ii)
(b) (ii) and (iii)
(c) only (ii)
(d) (i) and (iii)
10. 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.