Physical and Chemical Changes Test

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Physical and Chemical Changes Test - 7

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Weekly Quiz Competition

Question 1
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Which of the following is a chemical change:

A
melting of ice

B
boiling of water

C
rusting of iron

D
tearing a paper

Solution

When iron comes in contact with air and moisture it reacts with it and forms a brownish layer on its surface due to the formation of its oxides.
This is called rusting of iron. It is a chemical change since the new substance is formed.
Melting of ice, boiling of water, and tearing of paper are all physical changes.
Hence the option $$C$$ is correct.
Question 2
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Corrosion is a chemical reaction that involves :

A
The inside of the object changing from an element to a compound

B
The surface of the object changing from an element to a compound

C
Nothing happens

D
The surface of the object changes from one element into another element

Solution

Corrosion is a natural process, which converts a refined metal to a more chemically stable form, such as its oxide, hydroxide, or sulfide.

The corrosion process is a chemical change because two substances react together to form a new substance.

When iron rusts, iron molecules react with oxygen molecules to make a compound called iron oxide.

The surface of an object is changing from an element to any compound such as oxide, hydroxide, sulfide etc.

Option $$B$$ is correct.
Question 3
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Rusting is a special term, given to the corrosion of which metal?

A
Zinc

B
Copper

C
Nickel

D
Iron

Solution

Corrosion is a natural process, which converts a refined metal to a more chemically stable form, such as its oxide, hydroxide, or sulfide.
Rust is a general term for a series of iron oxides, usually, red oxides, formed by the reaction of iron with oxygen in the presence of water or air moisture.
Rusting is the common term for corrosion of iron and its alloys, such as steel. Many other metals undergo similar corrosion, but the resulting oxides are not commonly called rust.
Rusting is a special term for corrosion of iron.
Question 4
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Iron pillar near the Qutub Minar in Delhi is famous for the following facts. Which of these facts is responsible for its long stability?

A
It is more than 7 meters high

B
It weights about 6000 kg

C
It was built more than 1600 years ago

D
It has not rusted after such a long period

Solution

The correct answer is 'It has not rusted after such a long period'. For not rusting after such a long period the 'iron pillar' is famous.
Question 5
1 / -0

Which of the following are chemical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal

A
only (ii)

B
(ii) and (iii)

C
(iii) and (iv)

D
(i) and (iv)

Solution

Rusting of iron is a redox reaction and its a chemical change, apart from this all others are physical changes.
The rusting of Iron (Iron in contact with water forms the anode and in contact with air forms the cathode. At the anode iron is oxidised to $$Fe^{2+}$$ and at the cathode oxygen is reduced to water
Question 6
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Classify the following as physical or chemical change.

Metallic sodium is soft enough to be cut with a knife.

A
Chemical

B
Physical

C
Both $$A$$ and $$B$$

D
None of these
Solution
Physical Change:
It is a process in which the substance experiences a change in its physical properties like shape, size, colour, volume, appearance, state etc.
There is no change in its chemical composition.
When sodium metal is cut, there are only changes in its shape. Therefore, it is a physical change.
Question 7
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Classify the following as physical or chemical properties.
Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.

A
Chemical

B
Physical

C
Both $$A$$ and $$B$$

D
None of these

Solution

It is a chemical property as electron exchange takes place and new compound forms in this reaction.
$$Zn+2HCl \rightarrow ZnCl_2 + H_2$$
Question 8
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Which of the following is not a physical change?

A
Boiling of water to give water vapour

B
Melting of ice to give water

C
Dissolution of salt in water

D
Burning of Liquefied Petroleum Gas (LPG)
Solution
- Burning of any substance is a chemical change because it results in the formation of new products and the change is also irreversible. So, option D is correct.
- Boiling of water, melting of ice and dissolving of salt in water are all physical changes. There are no new substances formed and these changes are reversible as well.
Question 9
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A change in the physical state can be brought about:

A
only when energy is given to the system

B
only when energy is taken out from the system

C
when energy is either given to, or taken out from the system

D
without any energy change

Solution

A change in a physical state can be brought about when energy is either given to or taken out from the system.
For example, if we give energy or heat to ice, it will convert to liquid water similarly if we took out the energy (or cool it) from the water it will convert back to ice.

Therefore, the correct option is ($$C$$).
Question 10
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Assertion: Physical change of a substance involves a change in all properties and composition of its molecules.
Reason: The change of a substance with alteration of the composition of its molecules without any change in its specific property is called physical change.

Read the above assertion and reason and choose the correct option from the following.

A
Both assertion and reason are correct and reason is the correct explanation of the assertion.

B
Both assertion and reason are correct, but reason is not the correct explanation of the assertion.

C
Assertion is correct, but reason is incorrect

D
Assertion is incorrect, but reason is correct

E
Both assertion and reason are incorrect

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Physical and Chemical Changes Test - 7

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Physical and Chemical Changes Test - 7

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Question 1

melting of ice

boiling of water

rusting of iron

tearing a paper

Solution

Question 2

The inside of the object changing from an element to a compound

The surface of the object changing from an element to a compound

Nothing happens

The surface of the object changes from one element into another element

Solution

Question 3

Zinc

Copper

Nickel

Iron

Solution

Question 4

It is more than 7 meters high

It weights about 6000 kg

It was built more than 1600 years ago

It has not rusted after such a long period

Solution

Question 5

only (ii)

(ii) and (iii)

(iii) and (iv)

(i) and (iv)

Solution

Question 6

Chemical

Physical

Both $$A$$ and $$B$$

None of these

Solution

Question 7

Chemical

Physical

Both $$A$$ and $$B$$

None of these

Solution

Question 8

Boiling of water to give water vapour

Melting of ice to give water

Dissolution of salt in water

Burning of Liquefied Petroleum Gas (LPG)

Solution

Question 9

only when energy is given to the system

only when energy is taken out from the system

when energy is either given to, or taken out from the system

without any energy change

Solution

Question 10

Both assertion and reason are correct and reason is the correct explanation of the assertion.

Both assertion and reason are correct, but reason is not the correct explanation of the assertion.

Assertion is correct, but reason is incorrect

Assertion is incorrect, but reason is correct

Both assertion and reason are incorrect

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