A liquid that has frozen is no longer considered to be a liquid. Bulkheads are larger than baffles. Bulkheads are liquid-tight and baffles have holes in them. Bulkheads are placed vertically while baffles are horizontal. The weight of the liquid One of these helps determine the amount of liquid you can load in a tank.
Liquid has more room to move in a partially-filled tank.
The air pressure is greater inside a partially-filled tank. Many semi trailer tanks are slanted so that the lower end is at the back.