I have noticed when making milkshakes that banana, vanilla and strawberry flavour powders sink immediately and dissolve, and take a long time to seperate from the milk.  On the other hand, chocolate powder floats on the surface, taking a long time (in excess of 20 minutes) to completely sink to the bottom, and then easily seperates into lumps and layers, requiring near constant mixing to kee it dissolved.

Does anyone know what difference there is between chocolate powder and other powders that gives it such different qualities?

Recently, a friend of mine did his 8th grade science fair project. He decided to test whether pure water, water with flour in it, or water with salt in it would evaporate (and thus be purified) the fastest. He found that the flour went the fastest, the salt was next, and the pure water was actually the slowest. He did say that he used the same volume of total liquid overall, not just the same volume of water, so that could have been a factor by decreasing how much needed to be evaporated. But the margin was too large for this to be the only factor. Does anyone know why this would happen?