Separation was lost when a PCT Controller coordinated a direct routing that allowed an aircraft to enter BWI airspace. The reporter claimed a runway change at BWI was not coordinated.

Narrative

I was working a C172 off of a satellite airport. The aircraft departed and I Radar identified it and instructed him to climb to 5;000. When he was five miles north of the departure airport he requested direct EMI; so I coordinated direct EMI via the land line with the sector that the aircraft was being handed off to. The other Controller approved direct EMI and asked what altitude the aircraft was climbing to. I told him 5;000. I instructed the C172 to proceed direct EMI. During this time BWI was in the process of switching from a west to east operation. I am aware that in an east operation the C172 would be in Final's airspace; but I was not made aware that a runway change was being made. I noticed a B737 approaching from the south on my scope heading northwest and descending. I did not know what altitude this aircraft was descending to; or that BWI was in the middle of a runway change; so I called traffic and lit my aircraft up on the Final Controller's scope. The C172 did not see the traffic. The Collision Alert went off and I observed the B737 begin to climb. Shortly thereafter the Supervisor of another area came over to me and instructed me to put the C172 on a 300 heading and switch him to the next sector.Recommendations: 1. Make the other areas aware of runway changes occurring at major airports; especially when it affects the airspace so drastically. 2. Make sure all the point outs are made to all sectors that will be involved.