NCERT Class VII Science Solutions: Chapter 6-Physical and Chemical Changes Part 2 (For CBSE, ICSE, IAS, NET, NRA 2023)
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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
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.