11. which has more mass, a 2 kg fluffy pillow or a 3 kg small piece of iron? more volume? why are your
answers different?

Mass: Iron

Volume: Pillow?

Explanation:

The iron is more massive as it has 3kg of mass compared to the pillow's 2kg of mass.

As for volume, I'm assuming it's the pillow as the iron is described as being small, but that's just an estimated guess. If there is a diagram given, you'll need to use it to help you. The volume of an object is the breadth × height × length. Unfortunately I don't have enough information to answer that properly.

Your answers are different as mass is the amount of matter in the object whereas the volume is the amount of space taken up by it. As these are different things, the answers will vary. You could also say mass and volume are not dependent on each other, so the measurements don't necessarily need to correlate.

heat the gas and measure the pressure