1) Instead of using the word "random",is it acceptable to say particles in a liquid move about in "different" directions?

2) Why does ice have a higher density than water vapour? Is it because ice has a greater mass in a fixed volume?

3) The statement "Particles in a gas are lighter than particles in a solid." is incorrect. Is it because a particle in a gas has the same mass as a particle in a solid and the difference is that a solid has more particles than a gas?

1 answer

1) Instead of using the word "random",is it acceptable to say particles in a liquid move about in "different" directions?
I think the alternative wording is fine.

2) Why does ice have a higher density than water vapour? Is it because ice has a greater mass in a fixed volume?
Yes, because water expands when it freezes.

3) The statement "Particles in a gas are lighter than particles in a solid." is incorrect. Is it because a particle in a gas has the same mass as a particle in a solid and the difference is that a solid has more particles than a gas?
If the particles in the gas and the solid are the same, of course they have the same mass. I think the word you are looking for is that the solid is more dense than the gas.