Physical and Chemical Changes Test

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Physical and Chemical Changes Test - 15

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Weekly Quiz Competition

Question 1
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Your lab partner mixed two colorless solutions in the test tube. He sees no observable changes in the resulting mixture and is unable to detect any temperature change. Based on these observations, what type of change has taken place?

A
Physical change

B
Chemical change

C
Periodic change

D
None of the above

Solution

In a periodic change, the events are repeated after regular intervals like day and night. In the given example, no such change is taking place.
When the two solutions are mixed, we cannot conclude it is a chemical change as no precipitate formation, no evolution of gas, no change in temperature, nor any other indication of a chemical change is seen. Thus the reaction can be considered to be reversible and, the change will be physical.
Hence the correct option is A.
Question 2
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Which of the following is an example of a physical change?

A
Mixing of baking soda and vinegar together to cause bubbles and foam.

B
Falling of a glass cup from the counter and its shattering on the ground.

C
Lighting a piece of paper on fire causing it to bum up and leave ashes.

D
Baking a birthday cake for your mother.
Question 3
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What kind of change is undergone when an electric bulb glows?

A
A physical change

B
A chemical change

C
Both physical and chemical changes

D
A permanent change

Solution

When an electric bulb glows, it is a physical change. As the light produced by the electric bulb is due to the heating effect of the conductor. Even though there is an occurrence of temperature change since no new substances are produced, it is considered to be a physical change.

Hence, option A is correct.
Question 4
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What conditions are required for rusting to take place?

A
Water only

B
Oxygen only

C
Water and oxygen

D
Water and carbon dioxide

Solution

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. It is the common term for corrosion of iron and its alloys, such as steel. Both water and oxygen are required to form rust from metal iron.
Question 5
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Rusting can be prevented by:

A
coating the object with paint

B
coating the object with grease

C
galvanizing

D
All of the above

Solution

Hint: A red-colored coat formed on iron by the reaction of iron with oxygen in presence of air is called rust.

Explanation:

Rusting can be prevented by various methods.

1. Coating the object with paint or grease can prevent rusting. The layer of paint and grease prevents the reaction of iron with air.

2. Galvanization is the best method to prevent rusting. To protect the iron from rusting it is coated with zinc because zinc possesses a higher negative reduction potential than $$Fe$$ so zinc will oxidized before iron and protects iron from getting oxidized.

Correct Option: $$D$$
Question 6
1 / -0

Take some clean iron nails and place them in the three test tubes prepared as under:
Test tube A: Contains boiled water and a thin layer of oil.
Test tube B: Contains dry air.
Test tune C: Testube half-filled with water.
All the test tubes are tightly closed after placing the nails. After some time what will you observe?

A
Nails placed test tube A rust.

B
Nails placed test tube B rust.

C
Nails placed test tube C rust.

D
None of these

Solution

In test tubes A and B, corrosion of nails will not take place.
For corrosion to take place, air (or oxygen), water and iron, three should be in contact.
In test-tube A, a layer of oil separates air from nails and boiled distilled water.
In test-tube B, because the air is dry, hence no moisture is present which can cause rust.
In test-tube C, rusting of nails takes place, as it has all the conditions necessary for rusting i.e. presence of air(oxygen) and moisture.
Question 7
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What are the different conditions for a chemical reaction to take place?

A
Close contact

B
Solution form

C
Heat

D
Light

E
All of these

Solution

1. Close contact— For a chemical reaction to take place the reactants should be brought in close contact i.e. they should be mixed.
2. Solution form— Some substances react with each other only when they are mixed in the solution form.
3. Heat— Some reactants need to be heated to undergo a chemical change.
4. Light— Some reactions take place in the presence of light.
Question 8
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What type of protection is galvanising?

A
Physical protection

B
Sacrificial protection

C
Physical and sacrificial protection

D
None of the above.

Solution

$$\textbf{Concept: }$$Galvanizing is the process of applying a protective zinc coating to steel or iron to prevent rusting.
$$\textbf{Correct Option: }C$$
$$\textbf{Explanation: }$$Zinc layer present on iron get oxidised as it is more reactive than iron and forms a layer of zinc oxide on it. As Zinc sacrifice itself to protect iron, it is physical and sacrificial protection.
Question 9
1 / -0

While forming crystals, it is important to :

A
evaporate to dryness to get purest possible crystals.

B
attach gas syringes to collect fumes.

C
not evaporate water of crystallization.

D
use high flames.

Solution

Crystals contain water of crystallization hence during the formation of crystals water of crystallization should not be evaporated. Also, crystallization is the process of the formation of crystals. Crystals are defined as highly organized molecules into a well-known structure.
Question 10
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Which of the following is true?

A
Rusting will take place in absence of water.

B
Rusting will take place in absence of air.

C
Rusting will not take place in presence of water and air.

D
None of the above.

Solution

Oxygen and water are the essential things required for rusting. Rusting will only take place in presence of water and air.

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Re-Attempt Weekly Quiz Competition

Physical and Chemical Changes Test - 15

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Physical and Chemical Changes Test - 15

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Question 1

Physical change

Chemical change

Periodic change

None of the above

Solution

Question 2

Mixing of baking soda and vinegar together to cause bubbles and foam.

Falling of a glass cup from the counter and its shattering on the ground.

Lighting a piece of paper on fire causing it to bum up and leave ashes.

Baking a birthday cake for your mother.

Question 3

A physical change

A chemical change

Both physical and chemical changes

A permanent change

Solution

Question 4

Water only

Oxygen only

Water and oxygen

Water and carbon dioxide

Solution

Question 5

coating the object with paint

coating the object with grease

galvanizing

All of the above

Solution

Question 6

Nails placed test tube A rust.

Nails placed test tube B rust.

Nails placed test tube C rust.

None of these

Solution

Question 7

Close contact

Solution form

Heat

Light

All of these

Solution

Question 8

Physical protection

Sacrificial protection

Physical and sacrificial protection

None of the above.

Solution

Question 9

evaporate to dryness to get purest possible crystals.

attach gas syringes to collect fumes.

not evaporate water of crystallization.

use high flames.

Solution

Question 10

Rusting will take place in absence of water.

Rusting will take place in absence of air.

Rusting will not take place in presence of water and air.

None of the above.

Solution

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