Tag: physical changes

Quizzes (0) Questions (79)

Questions Related to physical changes

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

Which of the following represents correct statement(s)?

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Salt can be obtained by ___________ of sea water.

  1. sublimation

  2. cooling

  3. evaporation

  4. heating
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. evaporation

  2. purification

  3. condensation

  4. crystallisation
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Crystallisation is an example of ____________.

  1. physical change

  2. biological change

  3. chemical change

  4. fundamental change
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $A$

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

A synthetic indicator phenolphthalein gives _____ colour in acidic solution.

  1. red

  2. blue

  3. pink

  4. colourless
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

Pick up the correct statement:

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
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.
Multiple choice chemistry change around us physical changes changes and their classification physical changes

Physical changes are ________.

  1. Temporary

  2. Permanent

  3. Irreversible

  4. Endothermic
Reveal answer Fill a bubble to check yourself
A Correct answer
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