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प्रश्न
Fill in the blank
A new substance is always formed in a _______ change.
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उत्तर
A new substance is always formed in a chemical change.
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संबंधित प्रश्न
FILL IN THE BLANK
In a ............ change, new substances are formed.
Fill in the blank:
The substances which undergo chemical change are called _______
State four conditions necessary for a chemical reaction to take place.
Match the column in the following table.
| Reactants | Products | Type of chemical reaction |
| BaCl2(aq) + ZnSO4(aq) | H2CO3(aq) | Displacement |
| 2AgCl(s) | FeSO4(aq) + Cu(s) | Combination |
| CuSO4(aq) + Fe(s) | BaSO4↓ + ZnCl2(aq) | Decomposition |
| H2O(l) + CO2(g) | 2Ag(s) + Cl2(g) | Double displacement |
Match the pairs.
| a. | Photosynthesis | i. | Tendency to lose electrons |
| b. | Water | ii. | Reactant in combustion process |
| c. | Sodium chloride | iii. | Chemical change |
| d. | Dissolution of salt in water | iv. | Covalent bond |
| e. | Carbon | v. | Ionic bond |
| f. | Fluorine | vi. | Physical change |
| g. | Magnesium | vii. | Tendency to form anion |
Define a photochemical reaction.
Define an electrochemical reaction.
Write the chemical reaction where the following changes are observed.
Precipitate is formed
What do you understand by precipitation reaction? Explain with examples.
State the main characteristics of chemical reactions. Give at least one example in each case.
Give an example of a photochemical reaction.
Explain the term ‘chemical reaction’ with special reference to – ‘reactants’ and ‘products’.
Give a word equation for the following reaction.
An exothermic reaction where both the reactants are gases, one of which is oxygen.
Give balanced equation for the following conversion affected by heat alone on the substance:
Hydrated copper sulphate to sulphur dioxide
Give balanced equation for the following conversion affected by heat alone on the substance:
Copper nitrate to nitrogen dioxide
Complete the table given below.
| Heat on ammonium dichromate | Name of neutral gas evolved |
Complete the table given below.
| Heat on copper carbonate | Test for gas evolved |
Classify the following processes into physical or chemical changes:
- Beating of aluminium metal to make aluminium foil.
- Digestion of food.
- Cutting of a log of wood into pieces.
- Burning of crackers.
Both CO2 and H2 gases are ______.
What are the chemical reactions that occur in everyday life?
