Atectonic plate is part of the earth’s lithosphere

Plate tectonicsis a scientific theory that describes the large-scale motion of Earth's lithosphere. This theoretical model builds on the concept of continental drift which was developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s.The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates. 

Hypothesis. why don’t you know this? i learned this stuff in like 5th grade

The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water