What are the elements in the first vertical line of the periodic table?

The first vertical row of elements are all alkali metals with the exception of hydrogen which is a transition metal. The elements are: Hydrogen(H) with an atomic number of 1 Lithium(Li) with an atomic number of 3 Sodium(Na) with an atomic number 11 Potassium(k) with an atomic number 19 Rubium(Rb) with an atomic number of 37 Cesium(Cs) with an atomic number of 55 Fracium(Fr) with an atomic number of 87

Explanation:

What do gases consist of?

Gases consist of small particles that have mass.

What evidence does this reading give that gas particles have mass?

An inflated basket ball weighs more than a deflated basketball therefore, particles must have a mass.

Why can gases be compressed easily but not liquids and solids?

The gas molecules are separated from each other by relatively a large distance. The space between the particles allow them to be pushed closer together. Liquid and solids can not compressed easily because particles are packed tightly.

Why can gases filled their container completely but not solids?

The particles of gas must be on constant rapid motion. Because of this motion gases immediately fill their container. These rapid moving particle can mix easily with each other so that gas released at one end of container quickly diffuse to other end.

What is the collision?

The particles of gas are on constant rapid motion. Because of this motion gas molecules colloid with each other and also with the wall of container. When they strike with each other and with the wall this is called collision.

What does reading compare gas particles to?

This reading compare the gas particles with the rubber balls in a empty room.

According to reading how gas particles are differ from rubber balls?

The balls strike with each other and also with the wall and hence their motion slow down but in case of gas particles their motion can  not slow down on collision. Because of it is happens then gas convert in to the solid or liquid. That's why it is not happen in case of gas molecules.