ATMOSPHERE Grade 8 Science
What is the atmosphere?? • Atmosphere is a thin layer of air or gases that surrounds earth and protects it from extreme temperature and harmful sun rays.
Composition of Air • Atmospheric gases include: nitrogen (78%), oxygen (21%), CO2 (0.04%), water vapor( variable amount ) , argon.
Difference of atmosphere now and in the past • Now the atmosphere contained more nitrogen carbon dioxide and less oxygen, 2 billion years ago simple organisms began producing oxygen, then green plants developed producing more oxygen also formed an ozone layer around earth
Importance of gases • Oxygen : is used for breathing in all living organisms and it is essential for burning. It is produced by photosynthesis process in plants. • Nitrogen :it doesn't help in burning , it is an important component of proteins inside the bodies and it is used in fertilizers. • CO2 is used by plants during photosynthesis and produced by respiration
What are the layers of the atmosphere?? • Lower layers: • Troposphere • Stratosphere • Upper layers: • Mesosphere • Thermosphere • Exosphere
Troposphere • The troposphere is the lowest layer of atmosphere .It extends between 0 and 11 (17)Km above earth’s surface. • It’s the layer where all living organisms live and it includes all weather phenomena . • The temperature and atmospheric pressure decreases as we go up in the troposphere
Stratosphere • 2nd layer of atmosphere extends between 11 and 50 Km above earth’s surface • The ozone layer is found about 18 to 48 Km above earth in the stratosphere, ozone gas consists of 3 atoms of oxygen (O3), life on earth depends on ozone layer as it protects earth from harmful ultraviolet rays of the sun, pollutants called (CFCs) are destroying the ozone layer. • The temperature in the lower stratosphere are lower than the upper stratosphere
Ozone • A form of oxygen that has three atoms instead of two in its molecule
The ozone layer • A layer of the atmosphere that protects life on earth by filtering out ultraviolet radiation from the sun
Mesosphere , thermosphere and exosphere • Mesosphere is a very cold layer , extends between 50 and 90 km, meteors burn in this layer. • Thermosphere is the hottest layer it extends between 90 and 400 Km . • Exosphere extends above 400 Km, spaceships fly in this layer