Question about going from exercises to songs

My frustration is that I can vocalize on vowels well, but not when I apply them to a song. I know my throat needs to stay open, however I can't seem to coordinate it. Do you have to be concious of raising the soft palate and stretching the throat by imagining an egg in the back of your mouth or yawning?

You don't want to try and lift the soft palate consciously. The only benefit to yawning is feeling the release of the larynx down. But yawning while singing is a bad idea. It pulls the tongue back so it clogs the pharynx. The challenge you are referring to (OK on exercises, difficulty on songs) is because when we pronounce the constantly changing words we move the throat and mouth too much which disturbs the poise of the voice. We need to be able to keep the larynx stable against the pressure of the breath while we pronounce changing words. This requires us to learn how to pronounce with moving the throat and mouth as little as possible so we can keep the instrument-like quality of the voice and not drop into a talking quality. Part of the situation is learning to keep the jaw out of the way, which requires more stretch than we are used to. To keep the larynx stable it is helpful to think of pronouncing the words from the bottom of the neck or the top of the chest. This encourages the larynx to lean into the breath instead of being over-burdened by the breath pressure. Hope this helps.