Physical and chemical changes

Rusting of zinc is a fast change. True or false.

(a)  

The colour change when copper sulphate react with iron is

• Reddish

• Black-ish

• Blue-ish

• Green-ish

In which type of change a new substance is formed?

• Physical change

• Chemical change

• Both of these

• None of these

Which among the following is a physical change?

• Cutting a log of wood in small pieces

• Burning of wood

• Ripening of fruit

• Cooking of food

Which of the following is a chemical change?

• Bursting of a fire cracker

• Germination of seed

• Coal formation from buried trees

• All of these

Which is a method to prevent rust?

• Crystallisation

• Galvanisation

• Sedimentation

• All of these

What is the formula for rust?

• Fe₂O₃

• Fe₃O₄

• FeO₂

• FeO

How crystal of pure substances are obtained?

• By crystallization

• By chromatography

• By peptization

• By all these methods

What will happen if carbon dioxide gas is passed through lime water ?

• Calcium carbonate is formed

• The lime water turns milky

• Both of these

• None of these

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