I am sick (e.g., I have a cold, etc.)
I am going to be sick (i.e., I'm going to vomit)
Try these on for size.
1. A desperately sick (ill)child,
2. ...when she became ill with leukemia .(Ill is better than sick for serious illnesses).
3. If you get sick. (ill)..
4. The kitchen now becomes totally ill equipped. (Not sick. Ill equipped means badly equipped).
5. Don't wait until illness (sickness) strikes before coming up with a sick-day (not ill-day)
6. ...feels less guilty about calling in sick (sick is more natural than "calling in ill").
7.One of her daughters is ill.(sick)
8. ...payment for sick leave... (Not ill-leave).
9. ...share hope and a hug with these sick kids! (ill)
10. ... If you know a child who's ill...(sick)
11. ...seriously ill children...(more natural than seriously sick.)
12. ..sick Leave...(Not ill leave).
13. ...Sick days...(not ill days)
14. ...called in sick (not ill) at least once when they weren't ill. (sick).
15. ...sick time allowance ...(not ill).
All the best,