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प्रश्न
Fill in the blank.
Melting of ice is a _______ change.
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उत्तर
Melting of ice is a physical change.
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संबंधित प्रश्न
How do the following help in bringing about a chemical change?
light.
Complete and balance the following chemical equations:
Zn + `"H"_2"SO"_4` `→`
(dil)
Write the missing reactants and products and balance the equations.
\[\ce{KClO3 ->[heat]}\] ___________+ ____________
What are oxides ?
FILL IN THE BLANK
A .............. change is a temporary change.
TRUE \ FALSE
A precipitation reaction takes place only in a solution.
TRUE \ FALSE
Electrolytic refining is a method in which a thin coating of a metal is done over another metal.
Define chemical reaction.
Write the chemical reaction where the following changes are observed.
Gas is evolved
Give reason for the following:
Blue solution of copper sulphate changes to green when a piece of iron is added to this solution.
Give an example of the following chemical changes.
A reaction involving
(i) Change of state
(ii) formation of precipitate
Give a chemical test to distinguish between the following gases.
HCl and Cl2
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of dilute hydrochloric acid to silver nitrate.
A chemical reaction is often accompanied by external indications or characteristics which include –
- Colour change
- Effervescence or gas evolved
- Evolution or absorption of heat
- Formation of a precipitate.
With reference to each of the above indications, state the external indication seen during – Addition of water to quicklime.
Give balanced equation for the following conversion affected by heat alone on the substance:
Ammonium dichromate to nitrogen
Give balanced equation for the following conversion affected by heat alone on the substance:
Zinc nitrate to nitrogen dioxide
Explain the term chemical reaction with special reference to reactants and products.
Give two examples where a chemical reaction is accompanied by a change in colour of the reactants and products on completion of the reaction.
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.
Arrange the following statements in correct sequence:
- One side is water-loving and other water-hating molecules.
- When you agitate the cloth, the dirt is surrounded by many molecules and taken away from the cloth.
- The dirt surrounded by the detergent molecules floats in the water making it dirty.
- Finally, the cloth is clean.
- The detergent molecules have two sides.
- Water hating goes and joins with dirt and oil in the cloth while the water-loving joins with the water molecules.
