C# How to have a scripted if statement last x amount of seconds

So we are making a game, and we have this code

         if (collider.gameObject.name == "GravPill")
             Physics2D.gravity = new Vector3 (0,-0.5F,0);
             rb.velocity = new Vector3(0,-10,0);
             StartCoroutine (ExecuteAfterTime(10));

The Coroutine is this:

     IEnumerator ExecuteAfterTime(float time){
         yield return new WaitForSeconds(time);
             Physics2D.gravity = new Vector3 (0,10F,0);
     }

Basically, we want our ball to lose gravity (Done) and revert back to the original after x seconds once a pill has been eaten (we have the pill set up, everything works except the effect (gravity being changed) lasting x seconds. it just carries on, infinitely through scenes.

I understand the code below is of poor quality, but we are learning, and for now we are happy the majority works. Thank you in advance