Take a moment to really think about what is happening at the molecular level here in each of your questions.
What IS sound. As in, at a molecular level what happens to the gases in the air when a sound wave propagates through them? How is sound transmitted from molecule to molecule?
Well, sound is a compressional wave the moves by molecules vibrating at certain frequencies and then bumping into each other to transmit that vibration to the next molecule. This vibration of molecules is a form of kinetic energy that can be transmitted from one molecule to the next. These bumping molecules are physically what the "compressional" part of the wave is made up of. What makes sounds so special is that these vibrations have a net non-zero direction. That is, they are directed in a particular direction. It is the essence of what makes up "sound".
Okay, so knowing that, what IS temperature? As in, at a molecular level, what happens to the gases in the air when temperature goes up or down?
Well temperature is also related to the level of kinetic energy in each gas. At higher temperatures, the molecules can vibrate faster, because they have more kinetic energy. The difference between the vibrations of sounds and the vibrations of kinetic energy is that kinetic energy is random, not directed. But because higher temperatures have higher energy, they will transmit a directed vibration (a sound wave) with higher speed.
So in higher temperatures, the speed of sound will be slightly higher.
Do you see if you think about the very basics of the physics how you can reason out the answer?
Your second question. Are you familiar with energy states in the atomic structure like electron energy levels? Have you learned yet that energy levels are "quantized", meaning that it takes a very specific amount of energy to raise an electron to the next energy state? Well what if a high-freq high-energy wave (say ultraviolet) raises one of those electrons two or more energy states, and then the electron "comes down" to it's base energy state in one or more steps? What would be the emission frequency of the light that is emitted by the atom as the electron loses energy to come down energy levels? It would be a lower energy wave, perhaps a blue wave.
