and Chemical Changes
Q1. Fill in the blanks.
Cutting a log of wood into pieces is a physical
Condensation is a physical change.
When carbon dioxide is passed through lime
water, it turns milky due to the formation of Calcium Carbonate.
Two methods by which rusting of iron can be
prevented are painting or greasing and galvanisation.
Changes in which only physical
properties of a substance change are called physical changes.
A medicine is the end product of a chain of
Formation of manure from leaves is a
physical change. False
Iron pipes coated with zinc do not get
rusted easily. True
Iron and rust are the same substances. False
The chemical name of baking soda is Sodium
Changes in which new substances are formed
are called chemical changes. True
Q3. What type of change is crystallisation?
It is a physical change.
Q4. What type of change is involved in rusting of iron?
Ans. Rusting of iron is a chemical change.
Q5. Write one property of stainless steel.
It does not rust.
Q6. What type of change is formation of manure?
Formation of manure is a chemical change.
Q7. Which of the two is permanent change chemical change or
change is a permanent change.
Q8. What do you understand by chemical change?
change in which one or more new substances are formed is called a chemical
Q9. State the conditions necessary for rusting of iron?
rusting, the presence of both oxygen and water (or water vapour) is essential.
Q10. What is galvanisation?
of depositing a layer of metal like zinc or chromium on iron is called
Q11. What is added to steel to make it stainless?
steel is made by mixing iron with carbon and metals like chromium, nickel and
Q12. Why formation of manure from leaves is a chemical change?
Formation of manure from leaves is a chemical change because manure formed has
a different composition from leaves.
Q13. Why souring of milk is a chemical change?
of milk is a chemical change because it results in formation of new substance.
Q14. What is rust?
If a piece of iron is left in the open for some time, it acquires a film of
brownish substance. This substance is called rust.
Q15. What is blue vitriol?
of copper sulphate pentahydrate are blue in colour. So, it is commonly known as
Q16. Name the two methods by which rusting of iron can be
methods by which rusting of iron can be prevented are
painting or greasing and by galvanizing.
Q17. What happens when baking soda is treated with vinegar?
(Acetic acid) + Baking soda (Sodium hydrogencarbonate) → Carbon
dioxide + other substances
Q18. Which technique is better for obtaining sugar from sugar
Crystallization is considered as a better technique for obtaining sugar from