Physical And Chemical Changes Test

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Physical And Chemical Changes Test - 2

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Weekly Quiz Competition

Question 1
1 / -0

A man painted his main gate that was made of iron. This is done in order to

(i) prevent it from rusting
(ii) protect it from the sunlight
(iii) make it look beautiful
(iv) make it dust free

Which of the above reasons is/are correct?

A
(i) and (ii) only

B
(ii) and (iii)

C
(ii) only

D
(i) and (iii)

Solution

Iron objects are painted in order to prevent rusting. This also improves the looks of the object.
Hence, (i) and (iii) are correct.
Question 2
1 / -0

Corrosion is a chemical reaction that involves

A
bulk material of the object changing from an element to a compound

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

C
wearing off of the surface due to friction with air

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

Solution

Corrosion is tarnishing of the metal surface due to reaction with atmospheric gases.
The reaction occurs at the surface of the metal which gets deposited with the compounds formed.
Question 3
1 / -0

During an activity, following three test tubes are set up:

Test tube 1: A shiny iron nail is placed in a test tube along with anhydrous calcium chloride. Mouth of the test tube is covered with cotton wool.
Test tube 2: A test tube is filled with boiled water and a shiny nail is dropped in it. A layer of oil is placed on the surface of water.
Test Tube 3: A test tube is filled with tap water and a shiny iron nail is dropped in it. The test tube is left open.

In which of the test tubes will rusting not take place when observed after a week?

A
1 and 2

B
2 and 3

C
1 and 3

D
1, 2 and 3

Solution

Presence of both air and moisture is essential for rusting to take place.
In test tube 1, moisture is not available as it has been absorbed by anhydrous calcium chloride.
In test tube 2, air is not available as it got expelled on boiling the water and the layer of oil prevents more air from dissolving in the moisture.
Hence, rusting will not be observed in test tubes 1 and 2.
Question 4
1 / -0

Identify the incorrect statement(s).

Statement I: All physical changes are spontaneous, but chemical changes have to be induced.
Statement II: All changes, physical as well as chemical, involve energy exchanges.

A
Only I

B
Only II

C
Both I and II

D
None

Solution

Statement I is incorrect as spontaneity of a process depends on the conditions available. Many physical as well as chemical processes are spontaneous under standard conditions. For example, evaporation of water is spontaneous and so is the reaction of Na metal with the water vapour in the air. Statement II is correct as both physical and chemical processes involve energy changes.
Question 5
1 / -0

Zinc oxide (ZnO) reacts with carbon (C) to produce zinc (Zn) and carbon monoxide (CO). The balanced chemical equation for the given reaction is ZnO (s) + C (s) → Zn (s) + CO (g). Which of the following substances is reduced in the given reaction?

A
ZnO

B
C

C
CO

D
Zn

Solution

The given reaction is an example of a redox reaction. In a redox reaction, the substance that either gains oxygen or loses hydrogen is oxidised and the substance that loses oxygen or gains hydrogen is reduced. In the given reaction, zinc oxide (ZnO) loses oxygen to form zinc (Zn). Hence, ZnO is reduced in the given reaction.
Question 6
1 / -0

Which of the following statements is not true about a substance that goes rancid?

A
Its smell changes.

B
Its taste changes.

C
Its colour changes.

D
It reduces in mass.

Solution

Rancidity is a term generally used to denote unpleasant odours, colour change and flavours in foods resulting from deterioration in the fat or oil portion of a food. There is no change in the mass observed, which is in agreement with the law of conservation of mass.
Question 7
1 / -0

Which of the following phenomena is not an indication of a chemical change?

A
Evolution of a gas

B
Change in shape

C
Change in temperature

D
Change in colour

Solution

Change in the shape of a substance does not indicate that a chemical change has taken place.
Question 8
1 / -0

The substances which prevent oxidation of food are called

A
oxidants

B
reductants

C
antioxidants

D
decomposers

Solution

Antioxidants are the substances used to slow down the process of oxidation.
They may be used to preserve food in order to prevent it from going rancid.

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Physical And Chemical Changes Test - 2

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Physical And Chemical Changes Test - 2

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Question 1

(i) and (ii) only

(ii) and (iii)

(ii) only

(i) and (iii)

Solution

Question 2

bulk material of the object changing from an element to a compound

surface of the object changing from an element to a compound

wearing off of the surface due to friction with air

surface of the object changes from one element into another element

Solution

Question 3

1 and 2

2 and 3

1 and 3

1, 2 and 3

Solution

Question 4

Only I

Only II

Both I and II

None

Solution

Question 5

ZnO

C

CO

Zn

Solution

Question 6

Its smell changes.

Its taste changes.

Its colour changes.

It reduces in mass.

Solution

Question 7

Evolution of a gas

Change in shape

Change in temperature

Change in colour

Solution

Question 8

oxidants

reductants

antioxidants

decomposers

Solution

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