Tag: physical changes

Questions Related to physical changes

Which of the following represents correct statement(s)?

chemistry changes around us crystallisation process of separating components of a mixture physical changes

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

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

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

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

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Correct Option: A
Explanation:

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

Salt can be obtained by ___________ of sea water.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. sublimation

  2. cooling

  3. evaporation

  4. heating

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Correct Option: C
Explanation:

On evaporation of seawater in shallow pools, salt along with impurities remain behind. Impured salt is taken in a tank and its saturated solution is prepared. In a saturated solution of salt, HCl vapours are passed. Chloride ions being common to both, it's concentration increases, and NaCl gets precipitated which is free from impurities.

The process of forming large crystals of pure substances from their solutions is known as __________.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. evaporation

  2. purification

  3. condensation

  4. crystallisation

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Correct Option: D
Explanation:

The process of forming large crystals of pure substances from their solutions is known as Crystallization. The principle of crystallization is concerned with the thermodynamic conditions of crystallization and the kinetics of crystal nucleation and growth.
Crystallization is the physical transformation of a liquid solution or gas to a crystal which is a solid with an ordered internal arrangement of molecules, ions or atoms.

Crystallisation is an example of ____________.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. physical change

  2. biological change

  3. chemical change

  4. fundamental change

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Correct Option: A
Explanation:

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 $A$

A synthetic indicator phenolphthalein gives _____ colour in acidic solution.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. red

  2. blue

  3. pink

  4. colourless

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Correct Option: D
Explanation:

Phenolphthalein [3,3-Bis (4- hydroxyphenyl)- 2 benzofuran- 1-one] 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 which can loose $H^{+}$ ions in solution.

State whether true or false :

Cutting a log of wood into pieces is a chemical change.

chemistry change around us physical changes changes and their classification physical changes

  1. True

  2. False

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Correct Option: B
Explanation:

Cutting a log to wood into piece does not change the composition of wood hence it is not a chemical change.


It can be defined as physical irreversible change.

Hence the given statement is false.

Changes in which only ____________ properties of a substance change are called physical changes.

chemistry change around us physical changes changes and their classification physical changes

  1. chemical

  2. physical

  3. biological

  4. environmental

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Correct Option: B
Explanation:

Physical properties $-$ Shape, state of the substance size etc.

because these changes does not change the composition of the substance

Pick up the correct statement:

chemistry change around us physical changes changes and their classification physical changes

  1. Boiling points of alkyl halides are greater than those of the corresponding alkanes.

  2. In water, the solubility decreases as $CH _3OH > C _2H _5OH > C _6H _5OH$.

  3. Aniline is a weaker base than ammonia.

  4. All of the above.

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Correct Option: D
Explanation:

$(A)$  Boiling point $X$ molecular mass of compound hence alkyl halide have greater boiling point

$(B)$  More is the mass of the compound, less is the solubility.
               ${ CH } _{ 3 }OH>{ C } _{ 2 }{ H } _{ 5 }OH>{ C } _{ 6 }{ H } _{ 5 }OH$

$(C)$  Lone pair of aniline in resonance hence a weaker base.

Iron rod turns red on heating. The change is a ___________ .

chemistry physical and chemical changes physical changes changes and their classification physical changes

  1. Physical change

  2. Temperature change

  3. Physical and chemical change

  4. Chemical change

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Correct Option: A

Physical changes are ________.

chemistry change around us physical changes changes and their classification physical changes

  1. Temporary

  2. Permanent

  3. Irreversible

  4. Endothermic

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Correct Option: A
Explanation:

In a physical change, the substances are not altered chemically. No new products are formed. 
A physical change can affect the size, shape or color of a substance but does not affect its composition. The substances may be changed to another phase (i.e. gas, liquid, solid) or separated or combined so physical changes are temporary.

Examples:
when ice melts
when sulfur is mixed with iron filings. 
breaking a glass 
dissolving sugar in water