Question

You weigh two different objects on the same scale in the same location earth.the weighs are different.which must be different about the two objects

Answer 1

Their weights could be different.
Their volumes could be different. 
Their densities could be different.

The volume for an ounce of lead is much different than an ounce of aluminum.

the weight of a cubic meter of balsa wood is much different (and much lighter) than a cubic meter of water. That's why the ancients used balsa for their rafts.

Answer 2

Explanation:

The two objects are being placed in the same location and on the same weighing scale which means that the factor of the gravitation is same for both the objects.

The difference in the weights of the two objects may be due to the difference in the :

Weights : Simply if the weights of two objects are different it means that both have different mass.

Density : Density is the ratio of the mass to the volume. If the volume of the two objects are same, the weights could be different because of the difference in the density.

Volume: If the two objects have different volume, then there must be difference in the weights.