Advertisements
Advertisements
प्रश्न
What is a chemical change? Give two examples of chemical change?
उत्तर
A chemical change is a permanent change in which the chemical composition of a substance is changed and a new substance is formed.
Examples:
Heating of copper carbonate
Formation of curd from milk
APPEARS IN
संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Formation of manure from leaves is a physical change.
Fill in the blanK
A .............is a substance which changes the rate of a chemical reaction without undergoing a chemical change.
TRUE \ FALSE
Ammonia is a good oxidizing agent.
Name three reducing agents ?
State four conditions necessary for chemical reactions to take place.
Name the type of chemical reaction shown by the following equation:
Fe + CuSO4 → FeSO4 + Cu
Give an example of a reaction where the following are involved
Heat
Give reason for the following:
Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.
Complete the following table and write your observations.
|
Hydrogen sulphide |
Ammonia |
Sulphur dioxide |
Hydrogen chloride |
|
|
Shake the gas with red litmus solution |
||||
|
Shake the gas with blue litmus solution |
||||
|
Apply a burning splint to a gas |
Name: A greenish-yellow gas.
Give a chemical test to distinguish between the following gases.
NH3 and SO2
Distinguish by heating the following in dry test tubs.
Copper Sulphate and copper carbonate
What do you observe when CO2 is passed through lime water first and then a little in excess.
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.
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 – Thermal decomposition of mercury [II] oxide.
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Ammonium dichromate.
Rusting of Iron: undesirable change:: Dead plants turn into manure: ______.
Two chemical species X and Y combine together to form a product P which contains both X and Y
\[\ce{X + Y -> P}\]
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.
Write a word equation for the chemical change, if any.
Rusting of iron is ______.
