40 minute layover at IAH to catch an international flight?

Hello,

I’ve got a flight going through IAH with a 40 minute layover, will this be enough time? I’m flying with United.

1. Depart Vancouver 8:00am – Arrive Denver 11:51am

2. Depart Denver 4:20pm – Arrive Houston 7:40pm

3. Depart Houston 8:20 – Arrive Buenos Aires 9:20am

I’m concerned about the arriving flight in Houston from Denver. I don’t know any gates or terminals yet, do you think 40 minutes is enough to catch the connecting flight?

Thank you all in advance!