In this visual representation, the gases of the atmosphere are shown as molecules(definition:Individual atoms bonded together which can be one or more elements.). We are now going to describe each gas of the atmosphere using its chemical formula (recall this from the activity, Stomach Chemistry).
Take nitrogen, for example. The chemical formula for nitrogen is N2. This means that two nitrogen atoms are bonded together, as shown in the image above.
In chemical formulae, the number of atoms of each element is represented by a subscript(definition:text written smaller and below the line) number.
A second example is methane, a gas found in small amounts in the atmosphere. Methane has a chemical formula of CH4. This means that the molecule is comprised of one carbon (C) atom and four hydrogen (H) atoms.
There are two oxygen atoms in a molecule of oxygen.
There are two hydrogen atoms and one oxygen atom in a molecule of water.
A molecule of carbon dioxide contains one carbon and two oxygen atoms.
You have already learned that we have a digestive system made up of different organs. The purpose of that system is to break down food so that it can be stored as energy for our bodies.
Now let's look at our respiratory and circulatory systems, which function as a different set of organ systems working together to deliver oxygen to our cells.
Watch this video for an introduction to the ways in which they do that.
Science can have a lot of terminology and sometimes this course will have words that are unfamiliar to you. Use these strategies to figure out the meaning of new words.
Oxygen in the air you breathe plays an essential role in the function of your body. Let's follow an oxygen molecule as it travels through the respiratory and circulatory systems. Click on the titles below to open.
Oxygen enters your body through your nose and mouth and then travels down your trachea. Note that this is not the same as the esophagus (in the digestive system) which carries food to your stomach. Your trachea is lined with cells that produce mucus to trap any particles that could damage your body. It branches off into the bronchus, which further branches into bronchioles that get smaller and smaller until they reach the alveoli, which are tiny sacs at the end of the branches. Think of it as a tree trunk whose branches eventually become small twigs, with the alveoli at the tip of the smallest twig
Very small, specialized blood vessels called capillaries surround your alveoli and pick up oxygen for transportation throughout your body.
The walls of the alveolus are so thin that gas can be exchanged through them. This process is called diffusion.(definition:movement of O2 from an area where there are many molecules (in the alveolus) to an area of fewer molecules in the capillary)
Oxygen (O2) is carried by red blood cells(definition:red, disc-like cells in your blood) throughout the body and makes blood appear more red.
We will discuss carbon dioxide (CO2) entering the alveoli later.
The blood carrying the oxygen travels from your lungs to your heart. It then enters your heart through the left atrium.
Your heart muscle contracts and the blood flows into the left ventricle.
Then your heart muscle contracts again, causing the blood to exit your heart and travel to the rest of your body.
A blood vessel which carries blood away from your heart is called an artery. Veins are blood vessels which carry blood toward your heart.
Oxygen is carried by red blood cells and transported throughout your body.
The cells in your body use oxygen to perform a chemical reaction called cellular respiration, which allows them to live and perform their functions.
These cells make up your body's tissues and are located throughout your body, including in the digestive system.
The food that you eat and the oxygen that you breathe react to form energy and carbon dioxide.
glucose (sugar from the food we eat) + oxygen → carbon dioxide + water + energy
All of the cells in your entire body - the lungs, the heart, the stomach or the intestine - need both oxygen and food to survive!
Your arteries get smaller and branch out until they become capillaries, where the oxygen carried by your red blood cells diffuses into the surrounding tissue cells.
At the same time, carbon dioxide (from cellular respiration) diffuses from the cells into your blood.
The capillaries then expand and turn into veins, where the carbon dioxide is carried through your blood to your heart.
The blood carrying the carbon dioxide enters the right atrium of the heart. Your heart contracts to push this blood into the right ventricle.
From here, the heart contracts again and the blood carrying carbon dioxide gets pumped back to your lungs.
Once in your lungs, the carbon dioxide that has been carried by your blood diffuses into the alveoli. This happens at the same time as oxygen is entering your bloodstream.
The carbon dioxide diffused into your lungs from your blood then travels back up through your bronchioles, bronchi and trachea to your mouth or nose, then back out into the atmosphere.
When a chemical reaction occurs, matter can change, but it cannot be created or destroyed.
This means that when there is a chemical reaction, like the cellular respiration reaction that happens in your body, the number of atoms of the elements present at the beginning of the reaction (reactants) is the same as the number of atoms of the elements present at the end of the reaction (products).
Chemical reactions can be expressed as chemical equations, using words or chemical symbols.
A word equation uses words instead of chemical formulae. For example, the formation of water as a word equation would be:
Below you will see the chemical equation for the formation of water using chemical formulae.
The chemical equation above indicates that the reactants are H2 and O2 and the product is H2O. You will notice that there are large numbers (coefficients) in front of some of the chemical formulae. This indicates the number of each reactant or product that is present.
For example, there are two H2 molecules in this equation.
Cellular respiration occurs when oxygen and food (glucose) react to form carbon dioxide and water.
Word equation: glucose + oxygen → carbon dioxide + water + energy.
Chemical equation: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy.
Reactants: glucose (C6H12O6) and oxygen (O2).
Products: carbon dioxide (CO2), water (H2O) and energy.
We have discovered that carbon dioxide (CO2) is created by our bodies during cellular respiration.
Carbon dioxide is also produced by the combustion (burning) of fossil fuels(definition:fuels such as natural gas, coal, gasoline, oil that are formed by geologic processes.) often used to heat our homes. When not enough oxygen is present, carbon monoxide (CO) can be produced by fossil fuel combustion.
This can occur if your furnace or fireplace is malfunctioning, or if too little fresh air is reaching your gas-burning appliance. It can also happen if you use a gas-burning appliance meant for outdoor use only (such as a barbeque or camping stove) indoors where there is not enough fresh air. Exhaust from a car left running in a garage or an enclosed space will also produce carbon monoxide because there is not enough oxygen present.
Carbon monoxide is extremely dangerous. If you do breathe it in, carbon monoxide attaches to your red blood cells instead of oxygen and is then transported through your body.
As a result, the cells in your body will not receive the oxygen they need to perform cellular respiration, which has the same effect as suffocation. Carbon monoxide poisoning can quickly result in death.
Complete the interactive activity below to investigate how low oxygen availability can produce carbon monoxide.
In Ontario, there is a law requiring all residences with gas-burning appliances, fireplaces and attached garages to have carbon monoxide detectors near sleeping areas.
Carbon monoxide has no smell, colour or taste, making it invisible and impossible to detect by humans. Carbon monoxide detectors are electrical devices which sound an alarm when carbon monoxide is detected.
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Your task now is to assess your own home for carbon monoxide safety. You are encouraged to perform this assessment with others who live there too.
Complete the following:
When I looked around my house, I found that ______________ (list observations here).
Based on these observations, I would say that _______________ (give conclusions, positive and/or negative).
Based on my investigation, I would give my home a grade of ___ because _____________ (provide main reasons based on conclusions).
An area that needs carbon monoxide safety improvement in my home is ______________ (if your home requires more carbon monoxide detectors, explain this here).
|Self Check - Carbon Monoxide Detectors|
|I have identified whether there are carbon monoxide detectors and gas burning appliances in my home.|
|I have given my home a grade on carbon monoxide safety.|
|I have drawn conclusions about the benefits of science and of knowing science by explaining my carbon monoxide safety grade.|