I believe you mean the angle of repose and it differs slightly depending on the type of sand.
Sand is not a homogeneous material.
Homogeneous
This mixture is not homogeneous.
no
Salt and sand is a mixture.
Finally divided sand may be homogeneous.
No, sea water with sand is not a homogeneous mixture. The sand would settle to the bottom, indicating that it is not evenly distributed throughout the solution.
I don't know
Beach sand is a heterogeneous mixture
No, carbon mixed with sand is not a homogeneous mixture. It would be considered a heterogeneous mixture because the carbon and sand do not completely mix at a molecular level and can be visibly distinguished from each other.
Sand with shells is a heterogeneous mixture because it contains different components (sand and shells) that are visibly different and can be separated easily. In a homogeneous mixture, the components are evenly distributed and not easily distinguishable.
Sand and pebbles is a heterogeneous mixture. A solution is a homogeneous mixture.