Which statement about gases is true?
they are made up of particles that always move very slowly.
they are made up of particles that travel in a curved path when in motion.
they are made up of hard spheres that vibrate quickly in stationary positions.
they are made up of hard spheres that are in random motion.

They are made up of hard spheres that are in random motions.

They are made up of hard spheres that are in random motion.

Explanation:

Solid state : In this state, the molecules are present as hard spheres. They are arranged in regular and repeating pattern. The molecules are closely packed that means they are fixed and vibrate in place but they can not move from one place to another.

Liquid state : In this state, the molecules are present as hard spheres. They are present in random and irregular pattern. The molecules are closely packed but they vibrate in stationary positions.

Gaseous state : In this state, the molecules are present as hard spheres and in irregular pattern. The molecules are not closely packed and they can move freely from one place to another and spread out.

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.