1) Carbon dioxide is a gas, so when 
is evolved in the reaction, it appears as bubbles. The gas released extinguishes the fire and it can turn lime water milky.
2) When 
is released in a decomposition reaction we can identify by the strong pungent smell of the gas released.
3) Saturated citric acid can cause corrosion of the metal layers present in the pipes. So, before draining out any acid it is neutralized so that the pipes and other plumbing works do not get damaged leading to leaks in the drainage system.
Extensive property is that which depends on the amount of matter in a sample. For example: mass, volume, size are all extensive properties
Intensive properties are independent of the amount of matter. These include; boiling point, melting point, color and so on.
In the given examples:
Both sample A and B have the same volume (1000 ml) i.e. the same extensive property. However, they have different freezing points i.e. different intensive property.
Ans: D) The two substances are not the same because their intensive property is different.
Explanation:
Gravitational potential energy
= mgh = (45kg)(9.81N/kg)(2m) = 882J.
