Tag: changes and their classification

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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

Multiple choice chemistry changes - physical and chemical physical changes changes and their classification physical changes

Maximum conductivity would be of : 

  1. $K _{3}Fe(CN) _{6}[0.1 M Solution]$
  2. $K _{3}Ni(CN) _{6}[0.1 M Solution]$
  3. $FeSO _{4}.Al _{2}(SO _{4}) _{3}.24H _{2}O[0.1 M Solution]$
  4. $Na _{3}[Ag(S _{2}O _{3}) _{2}][0.1 M Solution]$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Conductivity depends on the number of ions produced in solution. FeSO4.Al2(SO4)3.24H2O (Alum) dissociates into the most ions per formula unit compared to the complex salts listed, leading to higher molar conductivity.

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

Which of them is not the characteristics of a physical change?

  1. Change in the physical properties

  2. New substances are formed

  3. Reversible reaction

  4. Original substance can be riveted back
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

1) A physical change is temporary and is usually reversible.
2) No new substances are formed during a physical change.
3) There is no change in mass of the substance during a physical change.
4) There is no net absorption or release of energy during a physical change.

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

The process in which the state of a substance changes from solid to liquid is called:

  1. boiling

  2. condensation

  3. freezing

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

When a solid is heated, the particles are given more energy and start to vibrate faster. At a certain temperature, the particles vibrate so much that their ordered structure breaks down. At this point the solid melts into liquid. This temperature change from solid to liquid is called  the melting point. Each solid has a set melting point at normal air pressure, but at higher altitudes the melting point lowers.

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

On decreasing temperature, a liquid turns into solid. This is:

  1. condensation

  2. melting

  3. freezing

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

On decreasing temperature, a liquid turns in to solid, this process is called Freezing. Freezing or solidification is a phase transition state.
Most liquids freeze by crystallization. formation of crystalline solid from the uniform liquid. this is a first-order thermodynamic phase transition i.e as long as solid and liquid coexist the temperature of the whole system remains very nearly equal to the melting point due to slow removal of heat when in contact with the air, which is a poor heat conductor.

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

When a solid directly turns into gaseous state, it is called:

  1. sublimation

  2. condensation

  3. polymerisation

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

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram. The reverse process of sublimation is desublimation or deposition.