I have never seen it end up as a powdery residue. Dry ice undergoes a transformation directly from solid to carbon dioxide gas. That is called sublimation. It must be placed under high pressure to become liquid.
We did E. A couple of years ago the electric company told us in advance they were going to shut off our electricity DURING THE SUMMER for 8 hours for maintenance one day in July. So we bought dry ice and put it in one of those coolers so we could have refrigerated things during the day without opening the fridge. It didn't melt. But it slowly disappeared at room temp. What was left was powdery residue. I don't know how else to explain it. There wasn't a whole lot of it but the dry ice didn't just totally disappear either. So I wonder why you did not have the same experience we did? Any idea? Thank you for your reply.
This post was edited by RosieG at March 7, 2019 8:02 AM MST
Fun thing to do if you have a smooth surface such as a table or floor. Place the block on it and spin it and push it. If you have a smooth metal surface place the block on it and it will 'cry'. There are numerous fun things on youtube. I used to do this one as a demo. It's on youtube but I can't find it but this is what I did.
Element 99 