A ball is thrown straight upward and then returns to the earth. does the acceleration change during this motion

From the time the ball leaves your hand until it hits the ground, the only force acting on it is gravity, and its acceleration is 9.8 m/s^2 downward ... the acceleration of gravity. It doesn't change. By the way, this statement applies whether you throw it or just drop it, and no matter which direction you decide to throw it.