Valentine's Day Online Assignment Submission by Zhang Jie

Dots and Cross Diagram:


Carbon Dioxide (CO2) is a harmful substance (fatal if excessed amount is taken in) formed by bonding 2 oxygen atoms and 1 carbon atom. The type of bonding involved is Covalent Bonding, which occurs by sharing of electrons between atoms of non-metallic elements so as to achieve the stable electronic configuration of a noble gas. In this case, O=H=O, and thus each of the atoms has 8 electrons.

Oxygen (harmless): A colorless gas that has no smell or taste under room temperature and standard pressure or a pale blue liquid at −182.95 °C. It makes up 20.8% of the Earth’s atmosphere and it is essential for living. All living things take in oxygen for respiration to stay alive. Oxygen is also found in water, which is another essential factor of all living things. An oxygen molecule consists of 2 oxygen atoms.

Carbon (harmless): A solid that is either clear (diamond) or black (graphite) under room temperature and standard pressure that has no smell or taste. It is essential for living because it makes up 18.5% of human body (second most abundant after oxygen).
Carbon Dioxide (harmful): is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere.

Effects of Carbon Dioxide: The primary health dangers of carbon dioxide are:
- Asphyxiation. Caused by the release of carbon dioxide in a confined or unventilated area. This can lower the concentration of oxygen to a level that is immediately dangerous for human health.
- Frostbite. Solid carbon dioxide is always below -78 oC at regular atmospheric pressure, regardless of the air temperature. Handling this material for more than a second or two without proper protection can cause serious blisters, and other unwanted effects. Carbon dioxide gas released from a steel cylinder, such as a fire extinguisher, causes similar effects.
- Kidney damage or coma. This is caused by a disturbance in chemical equilibrium of the carbonate buffer. When carbon dioxide concentrations increase or decrease, causing the equilibrium to be disturbed, a life threatening situation may occur.

References:
http://en.wikipedia.org/wiki/Oxygen
http://en.wikipedia.org/wiki/Carbon_dioxide#Chemical_and_physical_properties
http://www.ehs.ufl.edu/Lab/Cryogens/oxygen.html
http://en.wikipedia.org/wiki/Carbon
http://www.lenntech.com/carbon-dioxide.htm