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प्रश्न
What do you understand by 'chemical reaction'?
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उत्तर
A chemical reaction is the process of breaking the chemical bonds of the reacting substances (reactants) and making new bonds to form new substances (products).
A chemical change or chemical reaction occurs when particles collide. Collisions occur when reactants are in close contact or by supply of energy.
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Iron and rust are the same substances.
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 |
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Sodium chloride
Multiple choice:
Thermal decomposition of sodium carbonate will produce
What do you observe when Cl2 is passed through potassium iodide (KI) solution.
Give a chemical test to distinguish between the following gases.
NH3 and HCl
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
Write some materials prepared by chemical changes.
Classify the following as physical or chemical properties
Most metal oxides form alkalis on interacting with water.
Classify each of the following, as a physical or a chemical change. Give reasons.
(a) Drying of a shirt in the sun.
(b) Rising of hot air over a radiator.
(c) Burning of kerosene in a lantern.
(d) Change the colour of black tea by adding lemon juice to it.
(e) Churning of milk cream to get butter.
