The physical properties of 10 gram of iron are the same as what property of 20 gram of iron

The answer would be true

Physical properties are characteristic that was not related to the chemical property such as color, density or boiling point. It should be same if the substance is the same. the difference in mass won't change it.
Mass and volume is the example of extensive property, so 10 gram of iron will have different extensive property than 20 gram of iron.

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water

C) the increase in atmospheric pressure pushes the walls of the balloon outward thus making it  is the answer.hope i you.