C. Frequency is a measure of how many waves pass by in one second.
Thermal energy gives the particles of the substance kinetic energy because temperature is an average measure of kinetic enegy of the particle. If we give them thermal energy the particle will move faster, gaining enough energy to escape and become free. For example, from solid to liquid, the particles would espace their fixed position and be free to move as a liquid.
2NO2 means that there is 2 oxygen atoms and one nitrogen with two sets of that. So its the third one
The change in pitch of a train's horn as it passes while you are
standing still can be described by the Doppler effect, but that
doesn't explain it.
