Carbon dioxide is used in many consumer products that require pressurized gas because it is inexpensive an nonflammable.
Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they are employed during the transportation and storage of ice cream and other frozen foods.
Solid carbon dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical.
Carbon dioxide is also used in the drinks and food that we consume everyday.
Activity
Can you name a few types of food that contain carbon dioxide?
Oxygen (O2) and carbon dioxide (CO2) are two of the most important gases in air.
Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere.
Joseph Priestly and Carl Wilhelm Scheele both independently discovered oxygen in 1774, but Priestly is usually given credit for the discovery.
The name oxygen was created by Antoine Lavoisier, who incorrectly believed that oxygen was necessary to form all acids.
Carbon dioxide is a chemical compound, the molecule of which consists of one atom of carbon joined to two atoms of oxygen (CO2).
It was first called "fixed air" by the Scottish chemist Joseph Black, who obtained it through the decomposition of chalk and limestone, and recognized that it entered into the chemical composition of these substances.
What are the properties of oxygen and carbon dioxide? Let's take a look at the table below.
There are many experiments that you can do to show that oxygen is needed for a fire to burn. Let's take a look at one of these experiments.
Procedure:
A candle is lighted, and when it is burning well, a glass jar (like a jelly jar) is inverted over the candle.
The water level is immediately marked.
After the candle stops burning, the water level is marked again.
The amount of air required for the candle to burn is calculated using the following formula:
Observation: When the burning candle is completely extinguished, water rises up and fills one-fifth (1/5) of the original volume of air in the glass jar.
Discussion: The glass that supports the burning of the candle makes up about one-fifth of the composition of air in the glass jar.
Since the oxygen makes up one-fifth of the volume of air, it can be concluded that oxygen is used in the combustion of the candle.
******* Facts:
The cork base keeps the candle afloat.
The glass jar contains nitrogen, carbon dioxide and water vapour.
When the candle completely burns out, water in the jar rises.
The height of air in the column is used to calculate the amount of air used.
The candle stops burning because all the oxygen in the jar has been used.
Air pollution occurs when the air is tainted or contaminated with substances that are harmful to living things and pollute the environment. These substances are called air pollutants.
Air pollution in the form of soot and dust not only irritates our eyes, but affects our lungs and respiratory system as well. Sometimes, it can even cause lung cancer. If carbon monoxide from vehicles is absorbed into our blood, it prevents our blood from absorbing oxygen. This will cause headaches and even brain damage. Some people die from carbon monoxide inhalation. Lead particles in the air, which are caused by flaking paint, can result in high blood pressure, or worse, brain damage in children.
2. Acid Rain
Sulphur dioxide and oxides of nitrogen dissolve in rainwater to form acid rain, which not only destroys trees in the forests, but also causes serious damage to property, animals and vegetation. Acid rain causes fish to die as they cannot live in acidic water. It also causes corrosion of buildings and structures such as bridges and fences.
3. Thinning Of The Ozone Layer
The thinning of the ozone layer is caused by chlorofluorocarbon (CFC) compounds, which are relesed into the air through the use of air-conditioning, aerosol sprays and refrigerators. When the ozone is thin, less ultraviolet rays will be absorbed by the ozone, causing more ultraviolet rays reaching the earth. Exposure to too much ultraviolet rays can cause disease like skin cancers and eye cataracts. Ultraviolet rays also kill organisms that are useful to humans, and cause damage to crops and plants.
4. Greenhouse Effect
The greenhouse effect occurs when carbon dioxide trapped in the atmosphere prevents heat from the earth from escaping into space. This causes rising temperatures on Earth. The melting of the ice caps in the polar region and global warming are the results of the greenhouse effect. When these happen, flood may occur in low-lying areas and some places may experience droughts.
The rather non-reactive nature of nitrogen balances the active nature of oxygen in air. It is also converted to plant nutrients by lightning and certain soil bacteria. Nitrogen is important to life processes. It is the backbone of amino acids, which are the building blocks of protein for all living things. Without nitrogen, even plants cannot maintain their structures.
Oxygen (O2)
Highly reactive; it is needed by all living things for respiration, that is to metabolise food into energy and excrete carbon dioxide gas. Without oxygen, we would be dead in minutes!
This gas is a product of respiration & combustion. Plants take in this gas through their leaves, keep the carbon portion of it and excrete the oxygen back into the environment through a process called photosynthesis. This gas has the ability to absorb radiated heat and thus, helps to keep the atmosphere warm.
The air in our atmosphere has some variable components to it as well. These variable components include water vapour, dust particles, and ozone. Although these are found in small amounts, they can have significant effects on weather and climate.
Water Vapour
The amount of water in the atmosphere varies between 1% to 4%. Why is such a small amount such a big deal? Water vapour is the source of all clouds and precipitation, and often that is the most common reason people think of for water. But water does other things too. It has the ability, like carbon dioxide, to absorb heat energy given off by the earth. It can also absorb solar energy. When water changes from one state to another, it absorbs or releases heat. This heat is often called latent (hidden) heat. This is the energy source that helps drives a lot of storms.
Dust
Dust is much more than just little specks of dirt. It includes microscopic particles that are invisible to the naked eye, including pollen, spores, and seeds. So why is dust a big deal? It acts as surfaces where water can condense or group together, forming clouds from which water droplets can grow large and fall to the ground as snow or rain. Without dust, you could not have clouds or fog. Dust can also absorb or reflect incoming solar radiation. When dust in the atmosphere is high, such as during the haze, the amount of sunlight reaching the earth's surface will decrease. Dust can also contribute to scattering light, giving rise to more orange and red sunrises or sunsets.
Ozone is a form of oxygen that combines three oxygeb atoms into one molecule (O3). There is very little of this gas in the atmosphere, and it is concentrated in the stratosphere. Ozone absorbs ultraviolet (UV) radiation, and without it the earth would be uninhabitable. There may be other components depending on the quality or condition of the air.
One of the most importance resources that the earth gives us is water. All living things, including humans, animals and plants, need water in order to survive.
While water is important to all living beings, it plays a different role for plants and for humans and animals. Let us differentiate the functions of water in human beings, animals and plants.
All the statements below tell us about the importance of water.
Importance of water to plants:
Water helps to support aquatic plants.
The process of transpiration involves water.
Water is needed for the germination of seeds.
Water helps to transport synthesised food to all parts of plant.
Water dissolves and transports mineral salts from the roots to the leaves.
Importance of water to human beings and animals:
Water dissolves and transports digested food to all parts of the living thing.
Water dilutes blood and enables it to transport oxygen efficiently.
A person will die of dehydration if he loses 20% of water from his body.
Water is important in excretion. It helps rid the body of unwanted substances.
Water controls body temperature.
Water keeps the lung moist for exchange of gases through respiration.
Water supports and maintains the body shape of invertebrates.
Water is needed in many household and daily activities.
