Changes around us

Which among the following is a physical change?

• cutting a log

• burning a wood

• ripening of fruit

• cooking of food

Which of the following statements is true?

• Setting of milk to form curd is a chemical change and reversible change.

• Spoiling of food is a chemical and irreversible change.

• Burning of paper is a physical and reversible change.

• Boiling of an egg is a physical and reversible change.

Study the venn diagram. What does centre point X represents?

• making paper boat

• Burning crackers

• Blowing a balloon

• rusting of a bicycle

Which change represents point 1?

• Evaporation of water

• chopping of vegetables

• Burning of wood

• setting of milk

Which change represents point 2?

• bursting of balloon

• condensation of water

• tearing a paper

• setting of Plaster of Paris

Which change represents point 3?

• tearing of paper

• burning of LPG gas

• bursting of cracker

• melting of wax.

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.

• the chemical change that can be reversed.

• a physical change that cannot be reversed.

• the chemical change that cannot be reversed.

Which of the following statement is incorrect for a chemical reaction?

• Heat may be given out but never absorbed.

• The sound may be produced.

• A colour change may take place.

• A gas may be evolved.

Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?

• It is more than 7 metres high.

• It weighs about 6000 kg.

• It was built more than 1600 years ago.

• It has not rusted after such a long period.

Two drops of dilute sulphuric acid were added to 1 g of copper sulphate powder and a then a 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:

• physical and chemical changes, respectively.

• chemical and physical changes, respectively.

• both physical change.

• both chemical change.