Tuesday, May 19- Earth Unit - The Atmosphere
Objective: Understand how the atmosphere makes life on Earth possible and get to know the layers of the atmosphere.
The air you breathe includes gases. Gases are defined as particles that vibrate and move freely at high speeds. The main gases in the air are nitrogen and oxygen. Air also includes solid particles like ice crystals, dust and salt. These gases and particles form the Earth’s atmosphere, which extends from the Earth’s surface to space.
Atmosphere is one of the things that makes life possible on earth. The three gases necessary for life are nitrogen, oxygen and carbon dioxide. The atmosphere has all of these. The atmosphere protects us from most of the sun’s ultraviolet light and keeps the planet at a temperature that sustains life. It also replenishes our freshwater supply through precipitation.
The composition of the atmosphere is mostly two gases: nitrogen (78%) and oxygen (21%) – so about 99 % of the atmosphere. Many living things need oxygen to breathe and use nitrogen to produce proteins. Nitrogen is also essential for plant growth.
The remaining 1% is a mixture of argon, carbon dioxide, water vapor, ozone and other gases.
Water vapor is the gas form of water. It’s the reason we have clouds, rain and snow. It also absorbs hear and plays a role in controlling the amount of energy the atmosphere absorbs.
Carbon dioxide also absorbs hear and helps regulate the energy in the atmosphere. It’s also part of plants photosynthesis – green plants convert carbon dioxide, sunlight and water into food and oxygen.
Ozone is a gas formed the addition of an oxygen atom to an oxygen molecule. Ozone blocks the UV rays from the sun before they get to the Earth’s surface. Ozone concentration is highest at about 20 km (a little more than 65,000) above the Earth’s surface. This is the ozone layer. Without the ozone layer, many living things couldn’t tolerate the exposure to the sun.
Water vapor and carbon dioxide help regulate how much energy the atmosphere absorbs and emits. They – and other gases like methane and nitrous oxide, occur naturally in the atmosphere and prevent the Earth from becoming too hot or too cold.
Tiny particles in the atmosphere – dust, sea salt, ice crystals and ash – provide a surface on which water vapor can condense into liquid or solid droplets, allowing clouds to form. Then rain or snow falls from the clouds – so we get water to drink, to grow plants, etc.
The atmosphere has several layers. Scientists look at the composition of the layers and how the air temperature changes to distinguish between the layers:
Troposhere – This layer is closest to the ground and is where weather happens. It extends to about 12 km above the Earth’s surface and contains almost all of the atmosphere’s mass. The carbon dioxide in the troposphere regulates the Earth’s temperature.
Stratosphere – This goes from the top of the troposphere to about 50 km above the Earth’s surface. Temperatures in the stratosphere rise with increasing altitude because the upper part includes the ozone layer that absorbs the sun’s UV radiation.
Mesosphere – This is the middle layer of the atmosphere (50-85 km above Earth’s surface). It is the coldest part of the atmosphere because very little solar radiation is absorbed here.
Thermosphere – This extends to about 500 km above the Earth’s surface. Here, the temperature increases with altitude and may reach 1000 degrees Celsius. Within the thermosphere is thee ionosphere, a region of electrically charged particles. Nitrogen and oxygen in the ionosphere also absorb solar energy. This is where the international space station is.
Exosphere – This is the outermost layer and blends into outer space – about 1,000 km above the Earth’s surface. This layer is very thin and composed of very light gases such as hydrogen and helium.
ASSIGNMENT: Explore the Earth's atmosphere on the NASA website. Then, take a virtual balloon ride and collect temperature data throughout the Earth's atmosphere. Email me with a paragraph telling me what you discovered (data collection) and what you think it means (hypothesis).