Physical and Chemical Changes Test

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Physical and Chemical Changes Test - 17

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Weekly Quiz Competition

Question 1
1 / -0

Dissolving sugar in water is an example of:

A
physical change

B
chemical change

C
neutralisation

D
None of these

Solution

Sugar dissolving in water is a physical change because in this change no new substance is formed and the process is reversible.
Question 2
1 / -0

Which conditions are necessary for rusting?

A
Oxygen

B
Sunlight, water and metal

C
Water, oxygen, a metal

D
Metal and oxygen

Solution

Rusting takes place when there is contact between water, metal, and oxygen.
$$4Fe\quad +\quad 3{ O }_{ 2 }\quad +\quad 2n{ H }_{ 2 }O\longrightarrow 2{ Fe }_{ 2 }{ O }_{ 3 }.n{ H }_{ 2 }O$$
(Iron) (oxygen) (water) (rust)

Hence the option C is correct.
Question 3
1 / -0

What effect does salt have on the corrosion of iron?

A
Absolutely none

B
Speeds up the reaction

C
Stops rust in it's tracks

D
Gives off a different type of rust

Solution

Salt in water speeds up the reaction. This is because lots of dissociated ions are present in salt. As salt is a strong electrolyte and hence this tremendously accelerates corrosion in saltwater.
Option $$B$$ is correct.
Question 4
1 / -0

Which of the following is a physical change?

A
Rusting of iron.

B
Burning of coal

C
Cooking food

D
Conversion of ice into water

Solution

When the physical form of a substance changes but not the chemical composition, such a change is a physical change. Physical changes are generally reversible. When we look at the options given, only the conversion of ice into water is an example of a physical change, plus it can be reversed.
Hence, option D is correct.
Question 5
1 / -0

Which of the following represents correct statement(s)?

A
Salt can be obtained by the evaporation of sea water.

B
The salt obtained during crystallisation is pure and its crystals are large.

C
After crystallisation, the shape of the crystals can be seen clearly.

D
Large crystals of pure substances cannot be formed from their solutions.

Solution

The option $$(A)$$ represents correct statements.
Salt can be obtained by the evaporation of sea water.
The salt obtained during crystallization is not pure and its crystals are small.
After crystallization, the shape of the crystals cannot be seen clearly.
Large crystals of pure substances can be formed from their solutions.
Question 6
1 / -0

When a magnesium ribbon burns in air, the ash formed is dissolved in water:

A
the solution of ash in water is basic in nature

B
the solution of ash in water is acidic in nature

C
the solution of ash in water is neutral in nature

D
none of these

Solution

On burning magnesium in air magnesium oxide is formed, when it is dissolved in water, a basic solution containing magnesium hydroxide is formed.
Question 7
1 / -0

Which of the following is a physical change?

A
Burning of coal

B
Photosynthesis

C
Dissolving sugar in water

D
Digestion of food

Solution

A physical change is a process in which the physical state of the substance is changed. Dissolving sugar in water is physical change as the solid sugar is converted to a liquid state in water, so it changes its physical state.
Hence option C is correct.
Question 8
1 / -0

The freezing point of pure water is ____________.

A
100 degree centigrade

B
50 degree centigrade

C
20 degree centigrade

D
zero degree centigrade

Solution

Freezing point is the temperature where a liquid converts into solid. Water converts into ice at zero degrees centigrade. So degree zero centigrade is the freezing point of water. Hence option $$D$$ is correct.
Question 9
1 / -0

Crystallization takes place by the process of :

A
evaporation

B
condensation

C
sublimation

D
liquefication

Solution

Crystallization takes place by the process of evaporation.
Question 10
1 / -0

Vacuum desiccator is used _____

A
for drying crystals

B
for purifying crystals

C
for separation of crystals

D
for the process of crystallisation

Solution

Desiccators are an economical and reliable way to assure dry, dust-free storage and organization of humidity-sensitive products valuable reagents in crystalline form. Proper storage conditions can be optimized by selecting a desiccator size, shape, and control mechanism best suited for the application.
The lower compartment of the desiccator contains lumps of silica gel, anhydrous calcium chloride to absorb water vapor. The substance needing the desiccation is put in the upper compartment, on a glazed perforated ceramic plate. The ground glass rim of the desiccator lid must be greased with a thin layer of vacuum grease.

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Physical and Chemical Changes Test - 17

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Physical and Chemical Changes Test - 17

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Question 1

physical change

chemical change

neutralisation

None of these

Solution

Question 2

Oxygen

Sunlight, water and metal

Water, oxygen, a metal

Metal and oxygen

Solution

Question 3

Absolutely none

Speeds up the reaction

Stops rust in it's tracks

Gives off a different type of rust

Solution

Question 4

Rusting of iron.

Burning of coal

Cooking food

Conversion of ice into water

Solution

Question 5

Salt can be obtained by the evaporation of sea water.

The salt obtained during crystallisation is pure and its crystals are large.

After crystallisation, the shape of the crystals can be seen clearly.

Large crystals of pure substances cannot be formed from their solutions.

Solution

Question 6

the solution of ash in water is basic in nature

the solution of ash in water is acidic in nature

the solution of ash in water is neutral in nature

none of these

Solution

Question 7

Burning of coal

Photosynthesis

Dissolving sugar in water

Digestion of food

Solution

Question 8

100 degree centigrade

50 degree centigrade

20 degree centigrade

zero degree centigrade

Solution

Question 9

evaporation

condensation

sublimation

liquefication

Solution

Question 10

for drying crystals

for purifying crystals

for separation of crystals

for the process of crystallisation

Solution

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