The density of water is about 1kg/m³, therefore is the substance has a density of less than 1kg/m³ then it will most likely float however if it is more than 1kg/m³ then it will most likely sink.
The atomic number is the number of protons
Dark energy and dark matter seem over analyzed, although they are no different than gravity and wind. Dark energy can be the pulling caused by black holes, stars, and large planets. Dark matter also is just the effect of cosmic dust and debris pushed from explosions but also pulling caused by distant gravitational bodies.
Endothermic - takes in heat from the surroundings
Iron is matter; since the smallest unit of matter is atoms, iron could be brokolen down into atoms. unlike iron, water is a molecule made from atoms that were chemically combined, so water could be broken down into molecules.
