A mixture of alcohol and water is homogeneous while that of oil and water is heterogeneous. explain

The solution is said the be homogenous, if it contains single phase. On other hand, heterogenous system contains, multiple phase.

In present case, when alcohol and water are mixed with each other, it forms a single phase. Also, concentration is uniform through out. Hence, it is referred as homogeneous solution.

On other hand, when oil and water are mixed with each other, it forms a two phase. Hence, it is referred as heterogeneous solution.

Polar nature of alcohol favors formation of homogeneous solution with water.