Can I use MacBook Pro ram in my iMac? Also over heating?

I just recently traded my macbook pro on Craigslist for a iMac. The MacBook Pro I used to have is mid 2010 13" dual core. I upgraded the ram to 8gb instead of 4gb before I traded it so I had the original ram from the MacBook Pro. When I got home set up the iMac (took about 5 hours, whole thing was messed up software) after I did that I wanted to see how easy it was to upgrade the ram as the say. So I took off the ram cover and then I thought about my other 4gb of ram from the MacBook Pro. I put it into the other 2 ports (4 toltal) and put the cover back and turned it back on. It booted very very slow than it did before but I clicked the apple and about this Mac and it showed all 8gb working. I restarted it again and it seems a little faster. Is this making the Mac slower or is it fine?

I have 1 more question so when I was wiping the Mac and stuff and setting it up and it got really really hot on the top of the iMac. Even after the installs finished and I waited it still was hot I downloaded istat pro and the hottest component was 62 degrease F. Is this normal?