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Some Useful Words For You To Know
Air – a mixture of gases, it is all around us
Carbon Dioxide – part of the air, the gas we breathe out
Oxygen – part of the air, the gas we need to breathe in
Nitrogen – this gas makes up most of the air around us
Evaporation – the process by which a liquid changes to a gas
Melting – the process by which a solid changes to a liquid
Flow – liquids and gases flow. A river for example flows downhill
Retain – to keep its shape. Solids (e.g. a chair) retain their shape
Gases And Breathing
Run in place very fast for a minute. Do you notice how hard you are breathing? What you are breathing is oxygen? You need oxygen to live. That's why you can only hold your breath for a certain amount of time.
You can't see oxygen. It's invisible. It is a gas. A gas is matter that has no shape or size of its own. Gases have no color.
Gases are all around you. You can feel gas when the wind blows. The wind is moving air. Air is many gases mixed together.
The Earth's Atmosphere
The Earth's atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth's gravity It contains roughly (by molar content/volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.
There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, people who travel
above an altitude of 80.5 km (50 statute miles) are designated astronauts. An altitude of 120 km (~75 miles or 400,000 ft) marks the boundary where
atmospheric effects become noticeable during re-entry. The Kármán line, at
100 km (62 miles or 328,000 ft), is also frequently regarded as the boundary
between atmosphere and outer space.
The sea-level composition of air (in percent by volume at the temperature of 15°C and the pressure of 101325 Pa) is given below
Name |
Symbol |
Percent By Volume |
|
| Nitrogen |
N2 |
78.084 % |
|
| Oxygen |
O2 |
20.9476 % |
|
| Argon |
Ar |
0.934 % |
|
| Carbon Dioxide |
CO2 |
0.0314 % |
|
| Neon |
Ne |
0.001818 % |
|
| Methane |
CH4 |
0.0002 % |
|
| Helium |
He |
0.000524 % |
|
| Krypton |
Kr |
0.000114 % |
|
| Hydrogen |
H2 |
0.00005 % |
|
| Xenon |
Xe |
0.0000087 % |
|
A picture of mountains surrounded by ‘clean’ air!!
More About Evaporation
Evaporation is the process by which water is converted from its liquid form to its vapor form and thus transferred from land and water masses to the atmosphere.
Evaporation from the ocean accounts for 80% of the water delivered as precipitation (rainfall), with the balance occurring on land, inland waters and plant surfaces.
What Causes Evaporation?
What are the causes of evaporation?
It would be difficult to find a more important process in our weather and climate system than evaporation. Evaporation, as we know, is the change of water from a liquid to a gas. Water is continuously evaporating from the surface of the Earth, literally pumping more and more water vapour into the atmosphere.
Averaged across the entire Earth, water evaporates from the surface at a rate of about 3 millimeters per day (about 1/8 of an inch). Over the tropical oceans, the value is much larger; over cold surfaces, it is much lower; and over deserts it is almost zero, since there is little or no water to evaporate. This change of phase (from a liquid to a gas) requires heat, called the "latent heat of condensation".
When water evaporates, it removes heat, lowering the temperature of the surface. For both water and land surface, most of this heat energy comes from the surface, not from the air. Evaporative cooling, along with convection, helps keeps the surface of the Earth from getting too hot.
Here’s some Interesting facts:
AVERAGED OVER THE WHOLE EARTH, EVAPORATION EQUALS PRECIPITATION: The only thing that keeps all of this evaporation from filling up the atmosphere with water vapour is precipitation. Rain and snow are continually forming within clouds and falling back to the surface, completing one element of the Earth's hydrologic cycle.
The latent heat of condensation, absorbed when the water evaporated, is released to the atmosphere when the water vapour condenses back into cloud water (or cloud ice). This source of heat helps drive clouds and most other weather systems. For instance, evaporation from the ocean surface is the primary source of energy for hurricanes.
The picture below shows evaporation taking place!!
Some Cool Links
Click on any of the link buttons below to find out lots of more cool stuff about gases etc.
Have fun!!!
Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
