(2) The crucible tongs contact the cylinder wall, which may cause the cylinder to rupture. Therefore, fill in: the iron wire contacts the wall of the gas container;
(3) The reaction rate is related to temperature, pressure and reactant concentration. Should fill in: reactant concentration;
(4)① Iron can react with oxygen to generate ferroferric oxide, so fill in: iron+oxygen? Ignite ferroferric oxide;
② Due to the high carbon content, there are many sparks when burning, so fill in: intense burning, sparks everywhere;
According to the phenomena provided in the table, we can know that iron with different carbon content burns differently, so we should fill in: the carbon content of iron wire is different.
Extended data:
Iron wire burns in oxygen to generate ferroferric oxide; When iron is heated to 500℃ in the air, iron reacts with oxygen in the air to produce ferroferric oxide; The blue-gray debris scattered around the anvil is mainly ferroferric oxide; Iron reacts with high temperature steam to generate ferroferric oxide and hydrogen; The main component of natural magnetite is ferroferric oxide crystal. Ferroferric oxide is an important common iron compound.
Ferroferric oxide is ferrite, that is, Fe2+Fe3+(Fe3+O4) (that is, 2+ and 3+ in front of FeFe(FeO4) represent the valence state of iron). In Fe3O4, iron presents two valence states, one iron atom presents +2 valence and two iron atoms present +3 valence, so Fe3O4 can be regarded as a compound composed of FeO and Fe2O3, which can be expressed as FeO Fe2O3 instead of a mixture of FeO and Fe2O3, and belongs to a pure substance.
Baidu encyclopedia-iron oxide