Assume the recommended single dose of ibuprofen for children over the age of two is 4.5 mg per pound (mg/lb) of body weight. Use this guideline to calculate a single dose in milligrams for a five‑year‑old child who weighs 49 lb.

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.