I will be traveling from Amsterdam to Paris by train. I will first go from Amsterdam to Brussels, then change trains and go from Brussles to CDG. About how long will it take to change trains in Brussels? There are two trains, one has an hour layover in Brussels, and one has an 8 minute layover. I would much rather take the latter train because it leaves later in the morning, but I am not sure 8 minutes is enough time to change trains.
The connection time depends almost completely on the distance between tracks your trains are on. If they are on the same platform your connection will take as little as 30 seconds. If they are farther apart 8 minutes could be tight. In general if the published schedule shows the connection it should be possible.
I agree with Jeff that if the connection is listed, it should work fine--under normal circumstances. However, since you have a plane to catch, you don't have the flexibility of taking a later train from Brussels if your first train is delayed. I'd play it safe and take the earlier train.