The model below shows the equation that represents how hydrogen and oxygen combine to form water. In this reaction, the properties of the product are the same as the properties of the reactants. 2H2 + O2 → 2H2O

You already know what type of fossil it is. It is a sea animal which means you already know the general location of the animal which would of been the beach. It is possible to determine how it became a fossil since you can assume that it was either washed up on shore or buried by another animal. Clams generally live for about 400 years so in order for it to be a fossil it would have had to of been dead a long time ago which would be more than 400 years. It could of been around in the Silurian period or the Devonian period since that is when clams practically ruled the oceans. 252 million years ago is when clam like organisms were dominant so you have the general time it could of been around.