Is blood a homogeneous or heterogeneous mixture

I'd vote for heterogeneous because white blood cells and platelets are not necessarily homogeneously distributed throughout the solution in vivo.

Homogeneous mixtures: air, blood, saturated sugar water.

Blood is homeogeneous mixture ... hence the need for a centrifuge to separate the components.

The uneven distribution of white blood cell components is not a proof of hetero or homo. If left on their own, without the help the centrifuge, they'll not adequately separate into an unmixed mixture.

Homogeneous mixtures: air, blood, saturated sugar water.

Blood is homogeneous mixture ... hence the need for a centrifuge to separate the components.

That would apply in-vitro (test tube), but not in vivo (within the body).

it all depends at what magnification were inspecting it.

That was my first thought too, fm.

In general, red blood cells are homogeneous within the plasma. White blood cells, and platelets, OTOH will congregate around areas of infection and/or injury and will not be homogeneously distributed in the plasma in the body. A tube of blood, however, when rocked on a rocker (as is done before performing a CBC, for instance) will be a homogeneous solution.

As farmer says, if you take a small enough sample and look at it under high enough magnification you won't have a homogeneous solution of the components.

I stand corrected. I'm emerging bloody but not unbowed.