Since temperature increases when the average kinetic energy of particles increases, what is happening to the added energy when the temperature remains constant while a substance is melting or boiling?

Which theory was contradicted by experiments with the photoelectric effect? light spreads out after it passes through a small opening. as soon as light strikes metal, electrons will be ejected. visible light, regardless of color, will cause the ejection of electrons when striking metal. the kinetic energy of ejected electrons depends on the frequency of light that strikes the metal.