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प्रश्न
Explain the term – ‘sublimation’. Is sublimation of naphthalene – a physical or a chemical change. Give reasons.
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उत्तर
It is the conversion of a solid – directly into gaseous (vapour) state and on cooling directly back to solid-state – without changing into a liquid state.
It involves a change of state-and hence it is a physical change.
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संबंधित प्रश्न
Fill in the blank.
A new substance is formed in a ............... change.
Chemical changes are accompanied by changes in energy.
Tick (√) the correct alternative from the choice given for the following statement.
A substance which can not sublime is
Tick (√) the correct alternative from the choice given for the following statement
Which one of the following is volatile in nature ?
Give the main differences between physical changes and chemical changes.
Which of the following are chemical changes ?
- decaying of wood
- burning of wood
- sawing of wood
- hammering of nail into wood
Classify the following as a physical or a chemical change.
Burning of coal
Potassium chloride is added to water and stirred. A salt solution is obtained, which is then boiled, leaving behind a residue.
- Is the above change physical or chemical?
- Name the residue which remains behind after the salt solution is boiled.
- Is the change reversible or not reversible?
- Are the composition and properties of the original substance altered?
- Give a reason why the above experimentation would not be possible if calcium carbonate was taken in place of potassium chloride.
Select the correct answer from the choice given below to complete the sentence
A change in which a substance retains its identity is a
______ change.
Assertion: The explosion of fire cracker is a physical change.
Reason: A physical change is a reversible change.
