If you take a fluid (i.e. air or water) and heat it, the portion that is heated usually expands.
Hadaad tirahdid daanyeer iyo kaluun ayaan tartansiinaya wax lagaa aqbalyo maaha, mid kastaaba meel ayu ku fiicanyahay, kaluunku dabaasha ayu ku dheereeya daanyeerkuna geedaha koritaankooda ayu ku dheereeya.