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प्रश्न
A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
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उत्तर
In this case, the changes cannot be reversed. This is because the cement that hardens up after getting wet cannot be obtained back.
संबंधित प्रश्न
A chemical equation is a statement that describes a chemical change in terms of
| 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 |
Explain by writing a word equation.
Hard water gets softened on mixing with a solution of washing soda.
Multiple choice:
Which of the following is not a characteristic of a chemical change?
What is observed in performing the following :
| Hydrogen | Oxygen | Carbon dioxide | Chlorine | |
| Litmus test | ||||
| Apply a burning splint to the gas | ||||
| Colour of gas | colourless | colourless | colourless | greenish-yellow |
| Odour of gas |
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A coloured substance which leaves a black residue and evolves two gases one of which is acidic and coloured and the other neutral and colourless.
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Lead nitrate.
Name the solid residual product formed reaction and state its colour during – thermal decomposition of the following substance.
Calcium hydroxide.
What kind of a change is associated with decaying of a plants?
Rusting of iron is ______.
