I dont know... Overall maybe... But I ate some uncoated maize puffs today and the static electricity from my moustache kept redirecting puffs I trew in my mouth to the sides. It was weird. And a mess.

Well I guess I do... Was once in the middle of a cow herd in the mountains when something startled them. Now 100 cows (mostly young bulls 1-2 years old so extra unpredictable) are fleeing down the mountainside in a panic. Kind of a miracle that none of them hit me.

If you want to measure the density of the material itself: try find out what material it is and then look the density up. Or weigh and measure it before foaming it up.

Depends on how exact it should be. I did an exercise on bread/baked goods quality control in uni once. You an either use a laser scanner to get a 3D model of whatever youre measuring (this is nice, because you can also get Information about coulour, but the scanner is expensive, you can measure pretty much anything though) or submersion in plastic beads / seeds (measure the volume before and after) this is extremly cheap and reasonably exact.

If it's a foam like whipped cream or stuff like cereal puffs: use a beaker and weigh But be aware that this is not the real density, but bulk density. You can look up some constants about which geometries have which void space in bulk and get an approximation for the density of the bulk good from the bulk density.