NCERT Class VII Science Solutions: Chapter 6-Physical and Chemical Changes Part 2
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Question 7:
Galvanisation is a process used to prevent the rusting of which of the following?
Iron
Zinc
Aluminium
Copper
Answer: A

Image of Galvanising Process
Question 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 -
Physical change that can be reversed.
Chemical change that can be reversed.
Physical change that cannot be reversed.
Chemical change that cannot be reversed.
Answer: A
Question 9:
Which of the following statement is incorrect for a chemical reaction?
Heat may be given out but never absorbed.
Sound may be produced.
A colour change may take place.
A gas may be evolved.
Answer: A
Question 10:
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:
Physical and chemical changes respectively.
Chemical and physical changes respectively.
Both physical change.
Both chemical change.
Answer: C
VERY SHORT ANSWER QUESTIONS
Question 11:
State whether the following statements are True or False:
When a candle burns, both physical and chemical changes take place.
Anaerobic bacteria digest animal waste and produce biogas.
Ships suffer a lot of damage though they are painted.
Stretching of rubber band is not a physical change.
Answer:
When a candle burns, both physical and chemical changes take place. (True)
Anaerobic bacteria digest animal waste and produce biogas. (True)
Ships suffer a lot of damage though they are painted. (True)
Stretching of rubber band is not a physical change. (False)
Question 12:
Melting of wax is a change where a solid changes to liquid state. Give one more such change which you observe in your surroundings.
Answer:
Melting of ice is also a change where solid changes into liquid state.
Question 13:
What kind of change is shown by tearing of paper?
Answer:
Tearing of paper is a physical change although, it cannot be reversed.