As we already know, all matter on Earth exists in the form of a solid, liquid, or gas, and that solids, liquids, and gases are all made of extremely tiny particles called atoms and molecules. But all three states of matter differ one from another.
In this lesson, we are going to learn in more detail about gases. We are going to discuss the following:
Gases are everywhere around us. Gases, like other forms of matter, have physical properties such as color, odor, and taste, but in general, gases tend to be colorless and odorless. Air that we breathe is a mixture of gases. Water steam and water vapor are water in the gas phase (A vapor is the gaseous phase of substances that are either solid or liquid at standard temperatures and pressures). Even inside our bodies, gases are present.
Gases are the state of matter in which particles are usually very far apart from one another, move very quickly, and aren't particularly attracted to one another. Gas is a state of matter that has no fixed shape and no fixed volume. The gas is an air-like substance, that expands to fill the space it is in. Gases have a lower density than other states of matter. There is a great deal of empty space between particles. Particles in gases have a lot of kinetic energy. They move very fast and collide with one another, causing them to diffuse, or spread out until they are evenly distributed throughout the volume of the container. One of the most remarkable features of gases is that they appear to have no structure at all.
Many elements exist as gases at standard temperature and pressure, while many other elements and compounds can become gases under certain circumstances.
Some examples of gas are:
Carbon dioxide (CO2) and oxygen (O2) are the most important gases for living organisms.
Usually, the 4 most abundant gases in Earth's atmosphere are:
* Do you know why do helium balloons float?
It is because molecules of Helium are lighter than the nitrogen and oxygen molecules of our atmosphere and so they rise above it.
Gases have the following measurable properties:
Let's discuss now the following characteristic of gases.
1.Gases have no definite shape or volume
The molecules of the gas are randomly moving. That allows them to expand or contract to assume the volume of the container they are filling. Therefore, a gas's volume will be the space of the container in which its molecules have a range to move. From this property, we can assume that gases are occupying more space than they would in their liquid or solid-state. Also, by changes in temperature and pressure, gases contract and expand by predictable amounts.
2. Gases are easy to compress
To compress mean decrease in volume of any object or substance resulting from applied stress. Compared to solids and liquids, gases will compress more easily. Why? It is because there is so much space between the gas molecules. So, when a gas is compressed, the gas particles are forced closer together, so the volume decreases, and the resulting pressure increases. The temperature increases as well. Compressed gases are used in many situations. One such situation is in hospitals when oxygen is often used for patients who have damaged lungs to help them breathe better.
3. Gases expand to fill their containers
Gases spontaneously expand to fill any container. But if the container is not sealed, the gas will escape. For example, let's imagine that we are in some room and have some gas in a closed bottle. The bottle is completely filled with gas. If we open the bottle, the gas will spread out within the whole room, so we can imagine the room as the new container for the gas. The gas expands to completely fill the room too. Because gases expand to fill their containers, we can easily assume that the volume of a gas is equal to the volume of its container.
4. Diffusivity
Two or more gases can mix quickly and easily with one another and can form a homogeneous mixture because there is a lot of space between the molecules. This process is called diffusion.
The relationship of pressure, temperature, volume, and amount of gas are discovered by the three fundamental gas laws.
Discussing gases we can meet different classifications of gases. Let's discuss some of them.
What are the elemental gases? Elemental gases are the gases that exist as gases at standard temperature and pressure. When the pressure is changed (higher or lower), or when the temperature is changed (higher or lower), then the element may exist in a different form such as in liquid form or solid form.
Noble gases are also known as inert gases or rare gases. They are located in Group VIII or International Union of Pure and Applied Chemistry (IUPAC) group 18 of the periodic table. The noble gases are:
With the exception of Oganesson, all of these elements are gases at ordinary temperature and pressure.
Pure gases can take several different forms. They might be made up of individual atoms, an example is the gas neon. Oxygen is also a pure gas because it is made of one type of item, but is an elemental molecule. Pure gases may also be compound molecules, which are comprised of different atoms. Carbon dioxide would be considered a pure gas, but it is also a compound molecule.
Mixed gases are gases that consist of more than one kind of pure gas.
An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to inter-particle interactions. The ideal gas concept is useful because it obeys the ideal gas law.
Real gases are non-ideal gases whose molecules occupy space and have interactions, consequently, they do not adhere to the ideal gas law.
Toxic gases (or noxious gases) are gases that are harmful to living things. Some toxic gases are detectable by odor, which can serve as a warning. Examples are carbon monoxide, chlorine, nitrogen dioxide, and phosgene.
Compressed gases are substances that are a gas at normal room temperature and pressure, and are contained under pressure, usually in a cylinder. Compressed gases can be classified as:
Gases have many crucial roles in life on Earth. Oxygen is the most important gas for animals and plants for the process of respiration (oxygen is ultimately the fuel that allows our cells to produce energy from the food we eat). Gases in the atmosphere allow plants to perform the process of photosynthesis. Water vapor (which is an atmospheric gas), is an essential part of the water cycle. Nitrogen is an important part of many cells and processes such as amino acids, proteins, and even our DNA. It is also needed to make chlorophyll in plants.
Some uses of the gas in everyday life include:
