Explanation:
When water is boiled in the flask . Some portion of it is evaporated out . Now when cork is placed on it and is placed in the ice box . It cools down , by which the pressure inside decreases .
Due to decrease of pressure , the boiling point of water also decreases . Now it can boil at lower temperature . Thus it starts boiling at lower temperature even , when placed in the ice box .
Answer:
NO
Explanation:
No, a machine cannot be 100% efficient. This is due to the movement of the moving parts siding against each other and causing friction. This friction is the one that creates heat and causes wear and tear between moving ports f the machine hence making the machine to decrease in efficiency with time
Answer:


Explanation:
k = Coulomb constant = 
Q = Charge
r = Distance = 8 cm
R = Radius = 4 cm
Electric field is given by

Volume charge density is given by

The volume charge density for the sphere is 

The magnitude of the electric field is 
It's a physical change. the water is changing it's physical state