Integrated Science

AIR PRESSURE

OBJECTIVES:

• 1. DEFINE AIR PRESSURE

• 2. DISCUSS THE IMPORTANCE OF ATMOSPHERIC PRESSURE IN WEATHER AND

EVERYDAY LIFE

INTRODUCTION

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WHAT IS AIR PRESSURE?

• AIR PRESSURE IS THE WEIGHT OF THE ATMOSPHERE PRESSING DOWN ON THE

EARTH. IT IS MEASURED BY A BAROMETER IN UNITS CALLED MILLIBARS. MOST
BAROMETERS USE MERCURY IN A GLASS COLUMN LIKE A THERMOMETER TO
MEASURE THE CHANGE IN AIR PRESSURE

IMPORTANCE OF AIR PRESSURE

• AIR PRESSURE IS ALSO ESSENTIAL IN OUR EVERYDAY LIVES EG, DRINKING FROM

A STRAW OR USING A PLUNGER

AIR PRESSURE IN WEATHER

• EARTH’S GRAVITY CAUSES THE DOWNWARD FORCE THAT WE KNOW AS WEIGHT.

SINCE THE PRESSURE DEPENDS ON THE AMOUNT OF AIR ABOVE THE POINT
WHERE YOU’RE MEASURING THE PRESSURE, THE PRESSURE DECREASES AS YOU
GO HIGHER.

• AIR PRESSURE CHANGES THE WEATHER. HIGH AIR PRESSURE MEANS GOOD

STABLE WEATHER WHILE LOW PRESSURE MEANS UNSTABLE WEATHER.

• AS YOU MOVE HIGHER ABOVE SEA LEVELS THE AMOUNT OF AIR PARTICLES

DECREASES. THIS CAUSES AIR PRESSURE TO BECOME LOW. THE PRESSURE THEN
RISES AND EXPANDS. WHEN THERE IS HIGH AIR PRESSURE THE PARTICLES ARE
MORE DENSE AND TOO HEAVY TO RISE.

• AREAS OF HIGH PRESSURE ARE CALLED ANTICYCLONES AND AREAS OF LOW

PRESSURE ARE CALLED DEPRESSIONS

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