Carbonyl compounds: suggest question

Propan-1-ol and propan-2-ol are each heated with acidified potassium dichromate(VI), $\ce{K2Cr2O7(aq)}$, and the product of each reaction is collected by distillation. The product formed from propan-1-ol is P and the product formed from propan-2-ol is Q.

The two products are tested separately.

1. A sample of P is warmed with Fehling's reagent. A red precipitate forms.
2. A sample of Q is warmed with Fehling's reagent. No precipitate forms.
3. A sample of Q is warmed with alkaline iodine solution. A yellow precipitate forms.
4. A sample of P is warmed with alkaline iodine solution. No precipitate forms.

Suggest the identities of P and Q, and suggest why each test gives the observed result.