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Ncert Exemplar Solutions Class 7 Science Physical and Chemical Changes
Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Exemplar Class 7 Science Book, Unit 6, Physical and Chemical Changes. Here students can easily find step by step solutions of all the problems for Physical and Chemical Changes, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.
Physical and Chemical Changes all Question Solutions :
Multiple Choice Questions :
Question no – (1)
Which of the following is a physical change?
Answer :
The correct answer is option – (d)
Melting of wax is a physical change.
Question no – (2)
Which of the following is a chemical change?
Answer :
The appropriate answer is option – (b)
Cooking of vegetables is a chemical change.
Question no – (3)
A chemical change may involve
Answer :
The correct answer is option – (d) any or all of the above
A chemical change may involve change in colour only, change in temperature only or evolution of gas only
Question no – (4)
Which of the following is/are true when milk changes into curd?
Answer :
The answer is – (c) (i), (iii) and (iv) are correct
True Statements :
(i) Its state is changed from liquid to semi solid.
(iii) It changes taste.
(iv) The change cannot be reversed.
Question no – (5)
A man painted his main gate made up of iron, to
Answer :
The correct option is – d) (i) and (iii)
A man painted his main gate made up of iron, to prevent it from rusting and protect it from sun.
Question no – (6)
Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?
Answer :
The correct option is – (d)
The fact is responsible for its long stability is that, It has not rusted after such a long period.
Question no – (7)
Galvanisation is a process used to prevent the rusting of which of the following?
Answer :
The correct answer is option – (a)
Galvanisation is a process used to prevent the rusting of Iron.
Question no – (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 –
Answer :
The correct option is – (a)
This indicates a physical change that can be reversed.
Question no – (9)
Which of the following statement is incorrect for a chemical reaction?
Answer :
The correct option is – (a)
The incorrect statement is – Heat may be given out but never absorbed.
Question no – (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:
Answer :
The correct option is – (c)
Ships suffer a lot of damage though they are painted.
Very Short Answer Questions :
Question no – (11)
Answer :
(a) When a candle burns, both physical and chemical changes take place
This statement is True.
(b) Anaerobic bacteria digest animal waste and produce biogas –
This statement is True.
(c) Ships suffer a lot of damage though they are painted –
This statement is True.
(d) Stretching of rubber band is not a physical change
This statement is False.
Reason : Stretching of rubber band is a physical change.
Question no – (12)
Answer :
Ice melting into water is another example of a solid changing into liquid state.
Question no – (13)
Answer :
Tearing of paper is a physical change and also irreversible.
Question no – (14)
Answer :
(a) → (iv) Sugar candy (Mishri).
(b) → (vi) Galvanization.
(c) → (v) Chemical change.
(d) → (i) Turns lime water milky.
(e) → (iii) Rust.
(f) → (ii) Physical change.
Question no – (15)
Answer :
(a) Making sugar solution is a Physical change.
(b) A physical change is generally Reversible.
(c) Grinding of wheat grain changes its size. It is a Physical change.
(d) Iron benches kept in lawns and gardens get rusted. It is a chemical change because a new substance is formed.
Question no – (16)
Answer :
(i) Beating of aluminium metal to make aluminium foil – Physical change.
(ii) Digestion of food – Chemical change.
(iii) Cutting of a log of wood into pieces – Physical change.
(iv) Burning of crackers – Chemical change.
Question no – (17)
Answer :
(I) Iron + Air + Water → Iron Oxide
(II) Copper Sulphate + Iron → Iron Sulphate + Copper
Question no – (18)
Answer :
(a) When carbon dioxide is passed through lime water white coloured insoluble calcium carbonate is formed which makes it look milky.
(b) The chemical reaction between acetic acid and sodium hydroxide carbonate produces carbon dioxide which burst out in the form of bubbles.
Long Answer Questions :
Question no – (19)
Answer :
(a) Melting wax and Melting ice are examples of physical changes that can be reversed.
(b) Cutting a paper and breaking a glass bottle are examples of physical changes that are not reversible.
Question no – (20)
Answer :
(a) A change in colour is observed
Example :
The reaction between copper sulphate and iron
Copper sulphate + Iron → Iron Sulphate + Copper
(b) A gas is evolved
Example :
The reaction between vinegar and baking soda
Vinegar + Baking soda → Carbon dioxide + other substance
(c) Sound is produced
Example :
Burning of a fire cracker produces sound
Question no – (21)
Answer :
(a) Do you think rust is different from iron?
Yes, rust is different from iron as rust is a iron oxide.
(b) Can you change rust back into iron by some simple method?
No, rust cannot be changed back to iron as it is an irreversible change.
(c) Do you think formation of rust from iron is a chemical change?
Yes, formation of rust is a chemical change as it the reaction between three substances to form a new substance.
(d) Give two other examples of a similar type of change.
Folding of paper and melting of ice are both reversible physical changes.
Question no – (22)
Answer :
(a) What changes do you expect?
The colour of the solution in the beaker changes from blue to green and a brown colored deposit is found on the surface of the iron nail.
(b) Are these changes chemical in nature?
Yes, these changes are chemical in nature as two or more substances have reacted to form two or more new substances.
(c) Write a word equation for the chemical change, if any
Copper Sulphate + Iron → Iron Sulphate + Copper.
Other Chapter Solutions :
👉 Heat
👉 Weather, Climate and Adaptation of Animals to Climate
👉 Soil
👉 Transportation in Animals and Plants
👉 Electric Current and Its Effects
👉 Light
👉 Wastewater Story
