Physical and Chemical Changes Test

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Physical and Chemical Changes Test - 18

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Weekly Quiz Competition

Question 1
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Which of the following is the most common solvent used for crystallization?

A
Organic solvent - benzene

B
Plain water

C
A salt solution

D
Dilute solution of sulphuric acid

Solution

The most common solvent used for crystallization is water. Water is capable of dissolving many substances compared to other liquids and is called the universal solvent.
Question 2
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A synthetic indicator phenolphthalein gives ________ colour in basic solution.

A
Red

B
Blue

C
Pink

D
Colorless

Solution

Phenolphthalein is often used as an indicator in acid-base titrations. It turns colourless in acidic solutions and pink in basic solutions. Phenolphthalein is slightly soluble in water and usually dissolved in alcohols for use in experiments. It is a weak acid that can lose $$H^{+}$$ ions in solution. Phenolphthalein molecule is colourless and phenolphthalein ion is pink in colour. When a base is added to phenolphthalein, the molecule turns into ions leading to more ionization as $$ H^{+} $$ ions are removed.
Question 3
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Solvent dissolve large amount of solute at________.

A
room temperature

B
boiling temperature

C
freezing temperature

D
less than room temperature but more than freezing temperature

Solution

The solvent dissolves a large amount of solute at boiling temperature, i.e an increase in temperature increases the solubility of the solute. As the temperature increases, the particles of the solid move faster which increases the chances that they will interact more with the solvent molecules.
As the temperature increases, the amount of solute that can be dissolved in a solvent increases generally is high at their individual boiling points.
Question 4
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All of the following processes involve a separation of either a mixture into its components or a compound into elements. For each, decide whether the physical process or chemical reaction is required.
a. Sodium metal is obtained from the substance Sodium chloride.
b. Iron filings are separated from the sand by using a magnet,
c. Sugar crystals are separated from sugar syrup by the evaporation of water.
d. Fine crystals of Silver chloride are separated from a suspension of the crystals in water.
e. Copper is produced when Zinc metal is placed in a solution of Copper (II) sulphate, a compound.

A
a, b, c, d, e - physical

B
a, d, b, c, e - chemical

C
b, c, d - physical ; a, e - chemical

D
e a, b - physical ; c, d - chemical

Solution

a) Electrolysis of NaCl gives Na- Chemical process

b) Iron filings are attracted towards magnet - a physical process

c) Evaporation of water from sugar syrup gives sugar crystals - a physical process

d) It is a physical process of separating suspended particles.

e) It is a chemical process, as copper is produced from a solution of Copper sulphate.

Thus (b, c, and d) are physical processes and (a and e) are chemical processes.

The correct option is C.
Question 5
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A substance appears coloured because:

A
it absorbs light at a specific wavelength in the visible part and reflects rest of the wavelengths

B
ligands absorb different wavelengths of light which give colour to the complex

C
it absorbs white light and shows different colours at different wavelength

D
it is diamagnetic in nature

Solution

A substance appears coloured because it absorbs light at a specific wavelength in the visible part and reflects the rest of the wavelengths.
Question 6
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The process of forming large crystals of pure substances from their solutions is known as __________.

A
evaporation

B
purification

C
condensation

D
crystallisation

Solution

The process of forming large crystals of pure substances from their solutions is known as $$\text{Crystallization}$$.
Option $$D$$ is correct.
Question 7
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Crystallisation is an example of ____________.

A
physical change

B
biological change

C
chemical change

D
fundamental change

Solution

The process of formation of solid crystals from a homogeneous solution is called crystallization. It is a physical change. Crystallization is the solidification of atoms or molecules into a highly structured form called a crystal. It can also refer to the solid-liquid separation and purification technique in which mass transfer occurs from a liquid solution to a pure solid crystalline phase.

For example Salt we get from seawater can have many impurities in it. To remove these impurities, the process of crystallization is used.

Hence, the correct option is $$A$$
Question 8
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Which of the following is a chemical change?

A
Explosion of dynamite

B
Sublimation of iodine

C
Melting of sodium in a nuclear reactor

D
Condensation of steam

Solution

Answer:- (A) Explosion of dynamite
Explanation:-
An Explosion Is a Chemical Reaction. When an explosion occurs, a solid material of relatively small bulk is transformed into a large volume of hot gases in a fraction of a second. The explosive breaks down chemically, and a great quantity of heat is released.
Question 9
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Which of the following is a physical change?

A
Rusting

B
Melting of steel

C
Burning of magnesium ribbon

D
Turning of lime water milky by carbon dioxide

Solution

Melting is a physical change. Steel melts when heated and changes back to solid form when it cools. Here, no new substance is formed.

The other changes - rusting, burning of magnesium ribbon, and turning of lime water milky by carbon dioxide, are chemical changes because the change results in the production of new substances.
Question 10
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Study the given Venn diagram carefully. Identify 1, 2 and 3.

A
1- Melting of ice, 2- Rusting of iron, 3- Cutting a log of wood

B
1- Glowing of bulb, 2- Bursting of tyre, 3- Crystallisation

C
1- Stitching of garments, 2- Burning of a match stick, 3- Burning of a candle

D
1- Melting of ice, 2-Decompositon of sugar, 3- Sublimation

Solution

Stitching of garments is a physical change, burning a matchstick is a chemical change and burning of a candle involves both physical and chemical changes.
Hence, option C is correct.

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Physical and Chemical Changes Test - 18

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Physical and Chemical Changes Test - 18

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Question 1

Organic solvent - benzene

Plain water

A salt solution

Dilute solution of sulphuric acid

Solution

Question 2

Red

Blue

Pink

Colorless

Solution

Question 3

room temperature

boiling temperature

freezing temperature

less than room temperature but more than freezing temperature

Solution

Question 4

a, b, c, d, e - physical

a, d, b, c, e - chemical

b, c, d - physical ; a, e - chemical

e a, b - physical ; c, d - chemical

Solution

Question 5

it absorbs light at a specific wavelength in the visible part and reflects rest of the wavelengths

ligands absorb different wavelengths of light which give colour to the complex

it absorbs white light and shows different colours at different wavelength

it is diamagnetic in nature

Solution

Question 6

evaporation

purification

condensation

crystallisation

Solution

Question 7

physical change

biological change

chemical change

fundamental change

Solution

Question 8

Explosion of dynamite

Sublimation of iodine

Melting of sodium in a nuclear reactor

Condensation of steam

Solution

Question 9

Rusting

Melting of steel

Burning of magnesium ribbon

Turning of lime water milky by carbon dioxide

Solution

Question 10

1- Melting of ice, 2- Rusting of iron, 3- Cutting a log of wood

1- Glowing of bulb, 2- Bursting of tyre, 3- Crystallisation

1- Stitching of garments, 2- Burning of a match stick, 3- Burning of a candle

1- Melting of ice, 2-Decompositon of sugar, 3- Sublimation

Solution

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