What happens to the air pressure as you go higher in the atmosphere?

As altitude rises, air pressure drops.

Explanation: As altitude increases, the amount of gas molecules in the air decreases—the air becomes less dense than air nearer to sea level.

Explanation:

Physical change: Generally, there is a change in state, shape or size with no formation of any new substance. These changes are reversible in nature.

Chemical change: Generally, there is a formation of any new substance. These changes are irreversible in nature.

Observation 1 : Water droplets form on the inside of the glass lid.

This means that water vapors produced from the heating of the water are get converted into liquid state that is into water.

This process of the conversion of gaseous phase into liquid phase is known as Condensation.

Since, only state of the substance is changing which means that it is a physical change.

Observation 2 : Bubbles rise as the water starts boiling.

This is is because when water starts boiling , molecules of water started getting converted into gaseous state that is into water vapors.

This process of the conversion of liquid phase into gaseous phase is known as Evaporation.

Here also only state of the substance is changing which means that it is also a physical change.