Online Learning

Hydrogen Sulfide:

Hydrogen sulfide is a harmful chemical compound formed by 2 harmless elements: hydrogen and sulfur. Hydrogen sulfide is a colorless, very poisonous, flammable gas with the characteristic foul odor of rotten eggs. It often results from the bacterial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers (anaerobic digestion). It also occurs in volcanic gases, natural gas, and some well waters. The human body produces small amounts of H2S and uses it as a signaling molecule.

Covalent bonding is involved. The sulfur atom shares electrons with two hydrogen atoms to achieve the electronic configuration of a noble gas to become stable.

Hydrogen sulfide is made up of hydrogen and sulfur. Sulfur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a bright yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals. It is an essential element for life and is found in two amino acids: cysteine and methionine. Its commercial uses are primarily in fertilizers, but it is also widely used in black gunpowder, matches, insecticides and fungicides. Elemental sulfur crystals are commonly sought after by mineral collectors for their brightly colored polyhedron shapes.

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u , hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's chemical elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Naturally occurring elemental hydrogen is relatively rare on Earth.

Liu Yu Xuan(23)2A2

Sources:wikipedia.org

Science Assignment by Lim Zheng XIang 2A2 (22)

Science Assignment

I am going to use nitrogen oxide as the harmful compound I am going to post on in this science blog. Nitrogen oxide, as seen from its name, is formed when Nitrogen and Oxygen, 2 harmless elements react chemically together.

Nitrogen Oxide is a harmful gas which pollutes our air and when it is dissolved in Rain water, it forms Acid Rain which is also harmful. Breathing in high levels of Nitrogen Oxide can lead to: swelling of throat, reduced oxygen intake, and/or death. It also contributes to Global Warming and hampers the growth of plants which also indirectly affects humans too. Nitrogen oxide can form with other pollutants to form toxic chemicals. Nitrogen Oxide, plus other ground-level ozone, can cause other major respiratory problems in high levels.

When Oxygen and Nitrogen react chemically together to form Nitrogen Oxide, the chemical bonding which occurs is a covalent bond as both oxygen and nitrogen are non-metals and that the electrons between the 2 elements are shared.

As you all know, Nitrogen Is used by plants when soil particles convert them into a form in which it is safe for the plants to use whereas the air we breathe in everyday consists of Oxygen. Thus both gases(or elements) are harmless. But when they react chemically together, they produce a harmful gas which is nitrogen oxide.

Nitrogen is a chemical element that has the symbol N, atomic number of 7, belongs to group V and has an atomic mass of 14.00674. Elemental nitrogen is a colorless, odorless, tasteless gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere. It is created by fusion processes in stars, and is estimated to be the 7th most abundant chemical element by mass in the universe. Oxygen is the element with atomic number 8 and represented by the symbol O. It belongs to Group VI in the periodic table and has an atomic mass of 15.9994. It constitutes about 1/5 or 21% of the Earth’s atmosphere. Nitrogen Oxide is formed when certain fuels (oil, gas and coal) are burned at a high temperature, such as combustion. Thermal Nitrogen Oxide is produced during the combustion process when nitrogen and oxygen are present at elevated temperatures. The two elements combine to form NO or NO₂. Nitrogen Oxide is generated by many combustion processes too. Nitrogen Oxide is also formed from the plants that manufacture explosives.

Please enlarge the dot and cross diagram for a better view :)

References:

http://www.belleville.k12.wi.us/bhs/health/environment/nitrogen_oxide.htm

http://en.wikipedia.org/wiki/Nitrogen

http://en.wikipedia.org/wiki/Oxygen

http://www.alentecinc.com/papers/NOx/The%20formation%20of%20NOx_files/The%20formation%20of%20NOx.htm

Signing off,
Zheng Xiang

Nitrous Oxide ( Eddie )

Hello Everyone !

I am Eddie and this blog post is for science online lesson. We must find a harmful compound formed by two or more harmless elements and I have chosen Nitrous Oxide which is formed by nitrogen and oxygen. Please take note that Nitrous Oxide is different from Nitric Oxide which is commonly confused by people.

Firstly, I would give a brief introduction about Nitrous Oxide. Nitrous Oxide is also known as laughing gas or sweet air. It is a colorless non-flammable gas at room temperature with a slightly sweet taste and odor. It is commonly used in surgery and dentistry for its anesthetic and analgesic effects. Nitrous Oxide is a major greenhouse gas and air pollutant.

Ok now, I will write about the two elements that make up Nitrous Oxide. They are Nitrogen (N) and Oxygen(O).

For Nitrogen, the atmosphere contains a estimated 78% of it and of course we breathe them in every time we breathe but do not use them. Thus, it is obvious that Nitrogen is harmless to us.

For Oxygen, we need to survive and carry out respiration. It is essential for our survival and thus is harmless to us but instead important to us.

Why is Nitrous oxide harmful ?

Nitrous oxide is harmful to us because firstly, it is a greenhouse gas with tremendous global warming potential. When compared to Carbon Dioxide, it has the ability to capture heat 310 times more. Secondly, Nitrous oxide's pressure curve is usually sensitive to temperature which may form shock explosives. Some common building materials such as stainless steel and aluminium can act as fuels with strong oxidisers such as nitrous oxide to ignite. Thirdly, exposure to nitrous oxide causes short-term decreases in mental performance, audiovisual ability, and manual dexterity. Long term exposure can cause vitamin B₁₂ deficiency, numbness, reproductive side effects, and other problems. With all this reasons that I have listed, I believe you can see that Nitrous oxide is really harmful to us when misused or exposed. For example, if you breath in excessive nitric oxide, it can lead to hypoxia, a lack of oxygen in the brain which can lead to death.

How is it formed?

Nitric oxide is formed by oxygen and nitrogen over a covalent bond which is the sharing of electrons over atoms.

This is the dot and cross diagram of the covalent bond of Nitrogen and Oxygen

This diagram is drawn by myself so please correct me if there is any mistakes :)

Sources :

http://www.askmehelpdesk.com/child-teen-health/laughing-gas-115951.html

http://www.alphagalileo.org/ViewItem.aspx?ItemId=67154&CultureCode=en

http://en.wikipedia.org/wiki/Nitrous_oxide

Done by : Eddie (21)

Science online lesson,Harmful compound by (chenming)

The harmful compound that i have found out is Sulfur dioxide(SO2), it consist of two harmless elements,oxygen and sulfur.

Sulfur dioxide is the product of the burning of sulfur

S₈ + 8 O₂ → 8 SO₂

the uses of the sulfur dioxide;

Sulfur dioxide is sometimes used as a preservative for dried apricots and other dried fruits owing to its antimicrobial properties, and it is sometimes called E200 when used in this way. As a preservative, it maintains the appearance of the fruit and prevents rotting.

Sulfur dioxide is also a good reluctant. In the presence of water, sulfur dioxide is able to decolorize substances. Specifically it is a useful reducing bleach for papers and delicate materials such as clothes. This bleaching effect normally does not last very long. Oxygen in the atmosphere reoxidizes the reduced dyes, restoring the color. In municipal wastewater treatment sulfur dioxide is used to treat chlorinated wastewater prior to release. Sulfur dioxide reduces free and combined chlorine to chloride.

The harmfulness

Sulfur dioxide is a major air pollutant and has significant impacts upon human health. In addition the concentration of sulfur dioxide in the atmosphere can influence the habitat suitability for plant communities as well as animal life.

dot and cross diagram

reference;

google.com

wikipedia.com

http://www.thestudentroom.co.uk/showthread.php?t=943010

LSS Science Online Lesson Done by Aloysius Chan

Formaldehyde

Formaldehyde is a compound which is made up the elements, Carbon, Hydrogen and Oxygen. Its chemical formula is CH₂O. It is a colourless gas that has a pungent odour and is very poisonous. It is used in the cigarettes and also to preserve the dead bodies. It can cause cancer, respiratory, skin and gastrointestinal problems.

Constituent elements:

Carbon is a harmless element that is non-metallic and tetravalent and thus, it makes four electrons available to form covalent chemical bonds. All forms of carbon are highly stable, requiring high temperature to react even with oxygen. This is so as its electronic configuration is 2.4 and thus, it is quite unlikely to become unstable as it needs to either gain 4 more electrons or lose 4 electrons. Unlike elements like Fluorine, which has an electronic configuration of 2.7, and thus, it is highly unstable.

Hydrogen is another harmless element that has an atomic number of 1. Although it is highly flammable, it is very abundant in the universe, but not as abundant on Earth. Thus, it is relatively safe on Earth. Stars also contain hydrogen. Hydrogen is also used in water, what we drink in everyday life. Hydrogen gas was also first artificially produced in the early 16th century, via the mixing of metals with strong acids. At standard temperature and pressure, hydrogen is a colourless, odourless, non-metallic, tasteless, highly combustible diatomic gas with the molecular formula H₂.

Oxygen is also a harmless element and at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colourless, odourless, tasteless diatomic gas with the formula O₂ an essential element in life. Oxygen is a member of the chalcogen group on the periodic table, and is a highly reactive non-metallic element that readily forms compounds with almost all other elements (eg. Carbon Dioxide(CO2), Water (H2O)). By mass, oxygen is the third most abundant element in the universe after hydrogen and helium and the most abundant element by mass in the Earth's crust, making up almost half of the crust's mass.

Thanks,

Aloysius

Sources:

http://en.wikipedia.org/wiki/Carbon
http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Hydrogen

http://www.quit-smoking-stop.com/harmful-chemicals-in-cigarettes.html

Hydrogen Chloride ( Jovian Tan )

The harmful compound that I came up with is Hydrogen Chloride which is a compound formed by Hydrogen ( H ) and Chlorine ( Cl ) . Both of which are non-metal and thus they go through covalent bonding to form Hydrogen Chloride.

HCl - Hydrogen Chloride is a harmful compound because of its acidic nature, hydrogen chloride is corrosive in the presence of moisture. Hydrogen Chloride can combine with water to form Hydrochloric Acid, which is a high corrosive, strong mineral acid, naturally found in gastric acids. ( HCl + H₂O → H₃O⁺ + Cl^– ) Even with the absence of water, Hydrogen Chloride can still act as an acid by dissolving in certain solvents. Eg. Methanol

Cl - Chlorine is not a harmful element. Instead, it helps us to prevent diseases from occurring. Chlorine was first added into the community system in the 19th century and it was instrumental in eliminating many types of waterborne diseases such as cholera. Saving thousands of lives. Some may argue that showering in chlorinated water may have certain risks, but without chlorine , more diseases and risks will occur.

H - Hydrogen the first element in the periodic table and with the atomic number and mass number of 1 is harmless. It takes up almost 75% of the air , because of its abundance we can conclude it is harmless.

Dot & Cross Diagram:

Sources :

http://www.google.com.sg/
http://www.wikipedia.org/

http://wiki.answers.com

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/atomic/covalentrev4.shtml

Done by:
Jovian Tan ( 31 )
2A2

LSS Online Learning - Hong Jin Xiang

The harmful compound that I have chosen is Carbon Monoxide.

The constituent elements of Carbon Monoxide(CO) are Oxygen(O) and Carbon(C). Both of which are non-metal,thus they go through covalent bonding to form Carbon Monoxide.

CO - Carbon Monoxide is a poisonous gas which is colourless, odourless and tasteless. It is produced from incomplete burning of anything that contains carbon(e.g oil, coal, wood). CO is harmful when inhaled. Carbon Monoxide takes away oxygen from the red blood cells, thus depriving vital organs such as the brain and heart of oxygen. Large amounts of CO if inhaled can be suffocate.

C - Carbon can be found everywhere, and it also comes in many different forms.Carbon can be in the form of graphite, which is found in pencil lead, or even in the form of a diamond in jewellery. We humans are made up of 18% carbon.

O - Oxygen is not only harmless, but essential for our survival. We breathe in oxygen every day. Our atmosphere is made up of about 21% oxygen. Even our bodies are made up of 65% of it.

My dot and cross diagram for Carbon Monoxide is above.

Sources:

http://www.chemicalforums.com/index.php?topic=4915.0

http://en.wikipedia.org/wiki/Carbon_monoxide

http://biology.about.com/od/molecularbiology/a/carbon_monoxide.htm

http://www.osha.gov/OshDoc/data_General_Facts/carbonmonoxide-factsheet.pdf

http://chemistry.about.com/cs/howthingswork/f/blbodyelements.htm

http://en.wikipedia.org/wiki/Carbon

http://en.wikipedia.org/wiki/Oxygen

Signing off,

Hong Jin Xiang (12)