How to animate particle size (Newtonian Physics) I'm making an animation of water droplets disappearing/drying up. I figured the best way to do this was to create a simple particle system and then animate the size so that towards the end of the animation, the particles "disappear". 

I've created a keyframe on the first frame, but when I go to create the second keyframe, it will not allow me to change the value...it snaps back to the original value of .04. 

Any help would be greatly appreciated.
If you go to the Physics>size tab under Newtonian, and either hover your mouse over the input box, and press  RMB>insert keyframe, or just press  I while hovering over the input box after setting the particles to the size you need for your scene. Do the same thing to set the scaling down at your later frame. In my example, it is 30 frames using a sphere as a dupli object.