C150 pilot departing JYO is distracted by the poor takeoff and climb performance on a hot day and forgets to monitor aircraft altitude and enters class B airspace. PCT offers a reminder.

Narrative

I was leaving Leesburg. I had filed an ADIZ flight plan; gotten my squawk code; and contacted departure. I was planning to go up by Gaithersburg to avoid the FRZ then through the VFR corridor between BWI and Andrews. Leaving Leesburg the winds where about 9 gusts to 18 coming down over the mountain. They where veering around; but most of the time favored 35. So I started my takeoff roll and could see the windsock shift to where they had turned to a slight tailwind. In addition the density altitude at the 400 foot airport was 2;400. Between all of this; once I got off the ground after about a 1;500 takeoff roll it took longer than usual for the air speed to come up to 70 MPH. At first I could only coax 100 FPM out of the plane. When I crossed the end of the 5;000 foot runway I was still only 100 FT AGL. And there are hills around. So I was really focused on putting some space between the ground and me; and steering towards flat ground with no obstructions; and where I would be out of the down draft coming down off the mountain. When I finally got a decent climb established I totally forgot about the 1;500 floor of the Class B for the first few miles and kept going right up to 2;300 where I leveled off. Then I heard Potomac Approach; 'Confirm your altitude is 2;300'. Me; 'That's affirmative'. Them 'The floor of the Class B in your area is 1;500. Please descend immediately' Which I did.