During the phase transition vapour --> liquid water, the temperature of the water does not change; the molecules of water release heat and the amounf of heat released is equal to

where
m is the mass of the water

is the latent heat of evaporation.
For water, the latent heat of evaporation is

, while the mass of the water is

so, the amount of heat released in the process is
Answer:
C) 100 joules
Explanation:
The kinetic energy of an object is given by:

where m is the mass of the object and v its speed.
In this problem, we have an object of mass m = 50 kg and v = 2 m/s, so by using the formula we can find its kinetic energy:

Base in your questions that ask what cause the bright lines seen in the emission spectrum and i think the best answer to that is the H2 gas is used when protons was heated so the electron absorb all the photons and get exited and resulted by given of a light.
Answer:
30
Explanation:
Assuming the velocity is 3π radians <em>per second</em>, the top will spin through an angle of ...
(3π radians/s)(20 s) = 60π radians
Since each revolution is 2π radians, that is ...
(60π radians)/(2π radians/revolution) = 30 revolutions