It takes the shape of the cup and it can be sucked through a straw
The strong nuclear force holds the nucleus of an atom together.
Somehow, it overcomes the electrical force of repulsion between protons in the nucleus, which all have the same charge but still stay close together somehow. (b)
As a system is cooled to its freezing point, the kinetic energy of the particles in the system will lower so the movement are much slower. Cooling means taking out heat from the system. This process is a physical change because it is only the phase of the system is changed and it is still the substance after the process.
The wavelength will remain unchanged.
Explanation:
The velocity 
of a wave in terms of its wavelength 
and frequency 
is
(1)
so if we double both the velocity and the frequency, the equation above becomes
(2)
Solving for the wavelength from Eqn(2), we get
We would have gotten the same result had we used Eqn(1) instead.
