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 * Cycles of the Atmosphere **

Objectives of Cycles of the Atmosphere Lessons

In this lesson the students will be able to identify the concepts and laws of nature found in the study of the Cycles of the Atmosphere including:

The greenhouse effect The cycle of water The cycle of oxygen and carbon dioxide The cycle of nitrogen

as demonstrated by 80% mastery on a 15 question multiple choice quiz.

Introduction Students their is a law in physics that states that energy is never lost, but only changed into different forms of energy. Well that is true of atoms too. The atoms that make up water are not lost in time. They continue to exist in the various phases of water, solid, liquid and gas. The same is true of nitrogen and carbon. The same nitrogen atoms that existed in dinosaurs still exist today in plants, animals and even humans. This is atoms cycle themselves over and over again through natural cycle processes.

This week we will study the Water, Nitrogen and Oxygen-Carbon Dioxide cycles.

LESSON

Greenhouse Effect The atmosphere acts like a big blanket that helps heat-up the surface of the earth. As visible sunlight strikes the surface of the earth 28% of it is reflected back out into the atmosphere. the atmosphere absorbs this “thermal” or heat energy and warms up. The warmed up atmosphere also radiates heat energy back to the surface again.

This cycle of heat entering the atmosphere heating the surface of the earth and repeating the process is called the greenhouse effect.

Only half, 50%, of the radiant energy from the sun that reaches the earth is absorbed by the surface of the earth. some amount is immediately absorbed by the clouds and some amount is reflected back out to space.

The light from the sun is called radiant energy. When the sun's radiant energy is absorbed by the earth's surface it heats up the surface. This heat then radiates infrared energy back out to the atmosphere, where is it is absorbed by the clouds and atmospheric gases. By the atmosphere absorbing the heat it keeps the earth protected in a "warm blanket" of gases. Because of this we are able to live on the earth.

Earth Without the Atmosphere Without the atmosphere our planet would be like the moon that has no atmosphere. Men who have walked on the moon needed "space suits" to do so. The moon's surface gets extremely hot during the day and extremely cold at night because there is no atmospheric gases to hold in the heat and keep the moon "warm" enough to sustain life. We could not live on the earth if our atmosphere did not exist.

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Watch the Water Cycle movie. Immediately when done take the Brain Pop Review quiz.  Then come back to this page and read the lesson on the water cycle below.

Water Vapor Students the substances in nature are all cycled. Water, oxygen, nitrogen, carbon dioxide, minerals, rocks and atoms, are all cycled through processes of nature, but are not lost.

This is especially true of water. If you see water on the ground and later in the day the water has “dried up”, that is, the water is gone, where did it go? Does it still exist? Yes it does. The water was evaporated into " water vapor ". Water vapor is water in the form of a gas. Gaseous water is invisible. It exists everywhere in the atmosphere. Where there are larger amounts of water vapor in the air our skin can feel it and we say it is “ muggy ”, or “ humid ” out.

Muggy, humid days means there is more water vapor, water gas, in the atmosphere we live in. In other areas of the earth’s atmosphere there may be less water vapor, like the air over the deserts. With very little water vapor in the air we say the air is "dry".

The water cycle put simple works like this. The water in the oceans, lakes and rivers and the water on the surface of the ground evaporates into the sky. This means the water turns into a gas and then rises up into the atmosphere. But this is invisible so we don't see it.
 * The Water Cycle **

The water in the sky is a gas, called water vapor. But when the temperatures up in the atmosphere get a little cooler the water vapor will condense as very small microscopic droplets on the very small microscopic particles in the air and form a cloud.

When the water vapor condenses into tiny water drops a cloud is formed.

When more and more water accumulates in the cloud eventually the tiny droplets become big enough to fall to the earth because of gravity. We call this rain.

Then the rain falls on the oceans, rivers and lakes the water has returned. The cycle is complete, and again the water can evaporate into the sky.

The water will also fall on the ground. Some of that water evaporates into the sky but some of it is absorbed into the ground. The water that is absorbed into the ground will sink down into the earth and form a reservoir of water called “ground water” or called “an aquifer”.

Ground water is what we use when we dig a well to pull up the water. Well water is ground water brought back up to the surface again.