One thing you can do to make sure the chapters know that your grades are on the upswing is have your rec writers highlight this. They can point out that despite your low first semester GPA, you have matured, learned time management skills and while working 20 hours a week pulled an X GPA your second semester. No matter what GPA they see, you will have gotten the pertinent information before their eyes plus an interesting back story. Good luck, and keep bringing that GPA up. Science majors are not very forgiving.