After the three days, what happens in each test tube? why? what is necessary for rust to occur? how does this activity demonstrate the fate of oxygen in earthâs early atmosphere, when iron in the oceans was still removing oxygen from the air?

The situation would be that, in a sealed tube,  there are 3 to 4 nails inside and a certain amount of calcium chloride was added. After three days, there will be no changes to be observed in the first tube since the oxygen is not enough to initiate a change and there is no presence of water. For the second test, the same situation is made but boiling water was filled in the tube. For this, no changes would still be observed since there is no moisture. For the last test, the same situation as the first but it is filled halfway with water. After 3 days, rust would be observed on the nails. In order for rust to happen, there should be water and oxygen. The oxygen in the early atmosphere of the Earth would react with iron present in the oceans thus producing iron ores.