Understanding Air

Author: Aatmesh; Learner; Age 14 years

This is an assigned project on Air. The Learner independently researches and documents results based on the pointers provided. Learners develop additional questions for exploration on completion and reflection on this project 

Questions that were explored

  1. What is air? What are the constituents of air?
  2. What is an atom, a molecule, an element,  a compound,  a mixture?
  3. What is a gas?
  4. What is an aerosol?
  5. What is foam?
  6. Explore oxygen, nitrogen, carbon dioxide, water vapor.  Find out as much as you think is important about each of these. Organize your answers.
  7. Describe evaporation
  8. Explore clouds
  9. Explore rain
  10. What is saturation and saturation point?  Explore and describe.
  11. Explore humidity.
  12. Explore dew point
  13. Explore atmosphere.
  14. Explore air pollution  and pollutants
  15. Explore gravity


  1. What is air? What are the constituents of air?

Air is the invisible gaseous substance surrounding the Earth, which comprises of different gases. Air consists of 78% nitrogen, 21% oxygen and 1% of other gases, such as water vapor. This 1% also contains dust and other such impurities.

  1. What is an atom, a molecule, an element, a compound, a mixture?

An atom is the base of any form of matter, also the basic unit of a chemical element. The atom of a substance, defines what the substance is. Everything is made up of atoms at its most basic level. Atoms themselves contain three things that make them work. Electrons, neutrons and protons. The protons and the neutrons form the nucleus of the atom, while the electrons orbit around the nucleus. Protons and electrons have opposite charges, while neutrons don’t have any.

Atoms make up molecules, which determine what kind of substance something is, how it works and how it behaves. For example, water is made up of two hydrogen atoms, and one oxygen atom. These atoms form a water molecule (H2O). Hydrogen and oxygen are elements, meaning that they are substances which cannot be split into simpler forms, whereas H2O (water molecule) is a compound, meaning that is made by the combination of two or more elements. These elements are chemically united to form a new substance, and cannot be separated by physical means.

A mixture is when two or more substances are mixed together, but not combined chemically. This means that a compound is not a mixture. A mixture can be physically broken down into the elements that make it up. For example, if you put sugar and water into a bowl and mix them together, you form a mixture.

  1. What is a gas ?

A gas is an air-like substance, that is fluid and can fill any space regardless of how much of it (gas) is present. Gas is the least stable form of matter and expands to fill a space equally no matter how large. The atoms in gas are not very close together, they are loosely spread out as opposed to solids, where the atoms are tightly packed (that is why solids are more dense). Our atmosphere is made up of gases like oxygen, nitrogen etc.

  1. What is an aerosol ?

Aerosols are collections of solid or liquid particles suspended in a gas, an example of aerosols is dust. Aerosols are also present in deodorant and other kinds of spray.  In a can, the aerosols are foam that has been enclosed under pressure  and gets released by propellant air. When a button is pressed, the air pushes out small foam bits that have been focused into a stream.

  1. What is foam ?

Foam is a substance where air or gas bubbles are trapped inside a solid or liquid. A sponge is a solid foam.

  1. Explore oxygen, nitrogen, carbon dioxide and water vapor.

Oxygen gas is one of the reasons that there is life on Earth, oxygen is present in water, air and almost everywhere. Oxygen is also a gas that makes up 21% of our air. Oxygen is actually an element, but is generally referred to as oxygen gas, that has two oxygen atoms fused together. A lone oxygen atom is very rare, whereas three oxygen atoms fused together (also known as an ozone molecule) are abundant in the stratosphere. Oxygen gas is made up of two oxygen atoms. It is represented as O2. Since oxygen gas is not the product of two different elements, it is not a compound.

Nitrogen another gas that is present in our air. This gas makes up 78% of the air we breathe. Nitrogen, like oxygen is actually an element, but commonly referred to as nitrogen the gaseous form. A molecule of  Nitrogen gas is made up of two nitrogen atoms (NO2). It is also not a compound.

Carbon dioxide is a colorless, odorless gas that makes up around 1% of air. Actually, carbon dioxide, water vapor and a few more gases make up that 1%. A molecule of Carbon dioxide is made up of one carbon atom and one oxygen atom, it is represented as CO2. Carbon dioxide helps life on Earth. Green plants convert carbon dioxide into their food and water. Carbon dioxide is a greenhouse gas, meaning that it causes global warming. Our atmosphere requires some amount of carbon dioxide, because it traps heat reflected from the Earth’s surface and keeps us warm. But if their is an excess, then it causes global warming. Many of the gases that make up 1% of our atmosphere are greenhouse gases. Even though greenhouse gases are present in such small amounts, they can cause global warming. Another greenhouse gas is water vapor.

Water vapor is the gaseous form of water. When water is heated beyond its boiling point, it turns into water vapor (it evaporates). This gas rises up to a certain point and then forms into clumps called clouds. Clouds carry rain, which after hitting the ground evaporate to form other clouds. This is the hydrological cycle. Water vapor is, like water represented as H2O and is a compound of two hydrogen atoms and one oxygen atom. Water vapor is also a greenhouse gas.

  1. Describe evaporation

Evaporation is defined as the process of turning from liquid into vapor. For evaporation to occur, the energy of each molecule must be high enough that it escapes the liquid and turns into vapor.

Evaporation doesn’t depend so much on the average energy in, say a pot of water, but on the energy that each molecule has. When a molecule has lots of energy, it bumps into another one and transfers some of this energy. If this keeps on occurring, some molecules will have higher energy than the others. The molecules with really high energy have so much that they rise to the top of the pot, and escape. Evaporation can occur at any temperature above absolute zero, because at any temperature above absolute zero, the molecules in a liquid are randomly moving.

  1. Explore clouds

A cloud is a visible mass of condensed water vapor. Clouds are essential to human survival, as they provide water in the form of rain. When water gets evaporated, the vapor (which is warm) rises. The higher the vapor rises, the colder it gets and soon, the vapor condenses back into minuscule water droplets around dust particles called condensation nuclei, that make up a cloud. Some clouds are darker in color because the water droplets are densely packed together. This causes the light that falls from above them to scatter after coming into contact with the water droplets, leaving the bottom with a scarce amount of light.

  1. Explore rain

When water gets evaporated, it rises through the atmosphere. When the vapor gets high up, it starts to condense due to the cold temperature. The atmosphere is full of tiny dust particles called condensation nuclei, which come from volcanic eruptions, dust storms, fires and pollution. When water vapor condenses, it clings to these microscopic specks. If there is enough cooling water vapor in the air, these accumulate to form clouds. After the amount of droplets in the cloud become very high, the droplets fall down and merge with each other, forming larger and larger drops that fall down  to Earth as rain.

  1. Explore saturation and saturation point

Saturation is the degree or extent to which something is dissolved or absorbed compared with the maximum possible, usually expressed as a percentage. Saturation point is the stage at which no more of a substance can be absorbed into a vapor or dissolved in a solution. Saturation plays a role in rainfall. How much water vapor a certain amount of air can contain before it is saturated and forms into a cloud depends on its temperature. Warm air can contain more water vapor than cooler air before becoming reaching its saturation point. This means that places with warmer air have heavier downpours, because the build up of water is higher (before it rains) when compared to colder air, so when the saturation point is exceeded, their is more water built up in warmer air. If something is saturated, it means that it has reached its saturation point unless specified otherwise.

  1. Explore humidity

Humidity is the amount of water vapor present in the atmosphere at any given time. Absolute Humidity, often just referred to as ‘the humidity’, is a measure of the actual amount of water vapor in a particular sample of air, whereas relative humidity is the amount of water vapor present in air to the amount needed for saturation at the same temperature. When a volume of air at a given temperature holds the maximum amount of water vapor, the air is said to be saturated. Relative humidity is the water vapor content of the air relative to its content at saturation. Saturated air, for example, has a relative humidity of 100 percent.

12 Explore dew point

Dew points indicate the amount moisture in the air. The higher the dew points, the higher the moisture content of the air at a given temperature. Dew point temperature is defined as the temperature to which the air would have to cool (at constant pressure and constant water vapor content) in order to reach saturation. If the dew point temperature is equal to that of the air, the air is saturated. Dew point and relative humidity both measure the sam thing, but dew point is considered more accurate because if the temperature is higher, then the air can hold more water vapor, so the relative humidity will not be that much. Even if it is extremely humid, the relative humidity might not be that high. Dew point is the temperature at which dew points would form, so it is not relative and therefore gives a better sense of how humid it really is.

13. Explore the atmosphere

The atmosphere is a sphere of invisible gases that surround our Earth. They are held in place due to gravity. The heavier substances, like iron and stone are all closer to the Earth’s core because they have a greater gravitational force. The very light substances like gases don’t have a great gravitational pull, so they are furthest away from the Earth’s core.

The word atmosphere literally means ‘a ball of gases’ in ancient Greek. Many other planets in the solar system have atmospheres. Our atmosphere consists of five layers. The first layer is the Troposphere (6-20 km high), followed by the Stratosphere (20-50 km high) and Mesosphere (50-85 km), the penultimate layer is the Thermosphere (85-690 km) and the last one is the Exosphere (690-10,000km). These layers all contain different gases, and the air we breathe is situated in the lowermost parts of the troposphere (from the ground up). The stratosphere has the ozone layer (which protects us from harmful rays) and is vital to human survival. Without our atmosphere, by day our planet would be scorching and unable to support life. By night our planet would lose all its heat and reach sub zero temperatures. A perfect example of this is the planet Mercury. Our atmosphere filters excess and harmful heat by day, and by night it captures some of the heat that we need in order to survive.  These gases that capture heat are greenhouse gases.

To be more precise, when rays from the Sun come down to Earth, ozone molecules filter them. Ultra violet rays cause harmful radiation that can result in eye cataracts and nasty skin burns. Ultra violet rays also kill plankton, (the base of the oceanic food chain) which would make all kinds of food scarce. Ozone molecules rebound U.V (Ultra violet) rays back into space, and let sun light (we can’t see U.V or Infrared rays as they are on both the extreme sides of the light spectrum, VIBGYOR) and heat in. At night, all the heat that has hit the Earth gets released back into space (Infrared rays), but before it escapes the atmosphere, greenhouse gases trap the heat to prevent the Earth from freezing. When there are too many greenhouse gases, it causes global warming.

14. Explore air pollution and pollutants

Air pollution is the process where air is contaminated and spoiled. It is defined as the presence in or introduction into the air of a substance which has harmful or poisonous effects. Air pollution occurs is many different ways, some of which affect a lot more than just us. CFC’s also known as chlorofluorocarbons, are chemicals that harm the ozone layer. When CFCs are released into the atmosphere, the begin an upward journey until they reach the ozone layer in the Stratosphere. When the CFCs reach the ozone layer, the CFC molecules, attach themselves to ozone molecules. When this happens, the CFCs take away two oxygen atoms from the ozone molecule turning it into a lone oxygen atom. This oxygen atom is useless against U.V rays and to top it off, the CFC with the addition of two oxygen atoms turns into a greenhouse gas. This has numerous harmful effects.

Greenhouse gases themselves, are air pollutants. They cause a phenomenon that will melt the polar ice caps, and kill millions of living beings. This is called global warming, or ‘the Greenhouse effect’. It is called the greenhouse effect because it is just what happens inside a greenhouse. In a greenhouse, Heat comes in through the glass roof. Then, when the rays are reflected off the ground, they get trapped in the glass roof. This makes the temperature in the greenhouse quite high. Greenhouses are actually used in places with cold climate, to keep the plants warm and help them grow. This works well, but if the entire planet were to turn into a greenhouse, the effect would not be pleasant.

15. Explore gravity

Gravity is the force that pulls or attracts to bodies of mass towards each other. Gravitational force depends on the mass of an object, not the weight. Mass is the amount of matter (anything that occupies space) in a certain object, whereas weight is the effect of gravity on a certain object. If a person with a weight of 100kg is standing on Earth, he might be 200kg on a larger planet, because that planet is pulling him closer to its core (that’s why astronauts feel lighter on the moon). The mass of the man wouldn’t change, it would be standard (unless he loses an arm or something). The more mass something has, the stronger gravitational pull it has. For example, if (in space, vacuum) a sphere that is 40 kg is in between a sphere that is 100kg and one that is 200 kg, the gravitational force or pull will be stronger in the direction of the 200kg one.  Gravity keeps planets in orbit around the Sun, and also keeps the moon orbiting our planet. This same force also keeps our atmosphere in place.

A project by Aatmesh…