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प्रश्न
Give the reason why the following is considered as chemical changes.
An iron nail kept open in the atmosphere rusts.
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उत्तर
Rust of iron is a chemical change as iron rust [Fe2O3χ H20] is a brown flaky powder having a different composition from original iron metal, which is an irreversible change.
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संबंधित प्रश्न
Fill in the blank.
Heat is .................... by a gas during the process of condensation.
Solve this crossword by using the clues that follow.
Across
1. Energy in the form of sunlight is absorbed by the green plants in this process.
4. The reddish-brown substance formed over iron in the presence of oxygen and moisture.
5. This change is permanent and irreversible.
6. The process in which a solid directly changes into gaseous state.
Down
1. It is the change that takes place in case of swinging pendulum of a clock.
2. Occurrence of this is a non-periodic change as well as a natural change.
3. It is a physical change
True or false
In a physical change no net energy change is involved.
Classify the following as a physical or a chemical change.
Burning of coal
Fill in the blank.
A change, which alters the composition of a substances, is known as a___________ change.
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
The dissolution of lead nitrate in water is deemed as a _________ change.
Ice, water and water vapour look different and display different ______ properties but they are ______ the same.
The change of state of a substance from solid to liquid and liquid to gas is ______.
Mention a few physical properties of a substance.
