Some small hybrid cars and sports utility vehciles also have spoilers. what is the purpose? is it the same or different from the spoiler on a sports car?

For the most part aesthetics but you could argue they reduce air turbulence in some cases which would lead to better gas mileage. On sports cars however the goal is usually down force which is not wanted on economy cars as it can actually worsen gas mileage.

I hope that answered your question.

The rocks expand when there hot/warm  and contract when they are cold.