Posted on

Molecules and Drugs

Question 1

(a)

The chemical forumla is C5H9N3.

(b)

(c)

N-H which is the ability to form hydrogen bonds with water.

Question 2 

(a)

C16H21N3

(b)

The similarities are a two-carbon chain with a nitrogen at the end and a three-atom sequence of N-C-N, the spatial placement of these pieces, and the flat 5-ring of histamine can also be considered similar to the flat 6-ring of the antihistamine.

Question 3

Drugs that produce a physiological response in the body 
  • Aspirin
  • Morphine
  • Estrogen
  • Amphetamine
Drugs that inhibit the growth of substances that cause infections
  • (Keflex) antibiotic
  • Penicillin

Question 4 

(a)

Herbal supplement manufacturers provide labels on their products regarding ingredients used and whether it has complied with the relevant regulatory authorities’ standards.

Advice on dosage and usage compatibility are also provided within the package of the product itself.

(b)

Singapore has Traditional Chinese Medicine Practitioners Act (Chapter 333A), Health Products Act, Medicines Act, Poisons Act, and the Health Science Authority of Singapore (HSA) has issued guidelines regarding the use of traditional medicine materials.

Traditional Chinese Medicines are regulated by HSA and manufacturers must comply with a set of safety and quality criteria before thy are allowed to be sold.

Posted on

The World of Polymers and Plastics

Question 1

Acetone dissolves the polymer, allowing the gas of the foaming agent to escape. The polymer collapses on itself and is denser because the gas has been removed.

Question 2 (a)

LDPE cannot be used in this application because it does not have the required strength.

Question 2 (b)

The molecules of HDPE must line up in a way that produces the required strength. Using a thin liner of HDPE allows sufficient flexibility.

Question 3

When the piece of plastic is stretched, the strip narrows and “necks down.” The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the three-dimensional structure is not reversible, and if the pulling continues, the plastic breaks. When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. The cellulose molecules in a paper are held far more rigidly in place and are not free to become aligned.

Question 4 (a)

The benefits for polymers intended for use in the body should far outweigh any risks. The two main properties are (1) stable over time of intended use and (2) non-toxic. Other factors to consider are low cost, lack of solubility in body fluids, lack of reactivity in body fluids, and the ease of implantation.

Question 4 (b)

(b)  Several different types of contact lenses are on the market and each uses a different type of polymer. Polymethyl methacrylate (PMMA), one of the earliest polymers used for rigid gas permeable lenses, is structurally similar to Lucite and plexiglas. Silicone-acrylate materials now are more commonly used under trade names such as Kolfocon. Newer rigid gas permeable (RGP) polymers contain fluorine: fluoro-silicone-acrylate polymers and fluoro-silicones. Polymacon (38% water) is typical of the polymers used for soft lenses and is a polymer of 2-hydroxyethyl methacrylate (HEMA). Other methacrylates include hioxifilcon (48% water) and methafilcon (55% water) or even lidofilcon (70% water). Manufacturers’ websites are good sources of information. Desirable properties include being nontoxic, permeable to oxygen, comfortable to wear, and inexpensive. Also desirable is the ability to conform to the shape of the eye and to be easily cleaned (if not disposable).

Question 4 (c)

As mentioned in the previous part, hard contact lenses are typically made of PMMA, a rigid non-gas permeable plastic. The soft contact lenses that replaced them are made of silicone, which is flexible and allows oxygen to reach the eye. Because of these properties, the soft lenses tend to be more comfortable.

Posted on

Neutralising the Threat of Acid Rain

Question 1 (a)

Coal-fired plants release sulphur dioxide, creating sulphate particles that are responsible for60 to 85 percent of the poor visibility in eastern parks. 

Question 1 (b)

Normal rain has a pH range of 5–6, so if the rainfall in this park is 10 times more acidic, the pH range must be 4–5.

Question 2 (a)

By hanging outside, you are not using the dryer. As using dryer requires energy consumption, by not using it, we are reducing the production of electricity.

Question 2 (b)

By using the public transport, more people share the energy and fuel consumption as compared to them having their own cars.

Question 2 (c)

Avoid using the machine multiple times as small loads can be reduced with bigger loads, reducing energy consumption.

Question 2(d)

Preventing heat and cold from escaping, reducing energy use.

Question 2 (e)

By buying locally produced produce, there is no need to ship the goods around with ships, trucks, planes, which are huge contributors of SO2 and NO2 that causes acid rain.

Question 3

Acids Bases
Hydrochloric acid (HCL) Sodium Hydroxide (NaOH)
(Sulphuric acid (H2SO4) Potassium Hydroxide (KOH)
Nitric acid (HNO3) Ammonium Hyrdoxide (NH4OH)
Carbonic Acid (H2CO3) Magnesium Hydroxide (Ma(OH)2)
Phosphoric acid(H2PO4) Calcium Hydroxide (Ca(OH)2)
Turn blue litmus paper pink

Tastes sour

Conduct electric current

 Turn red litmus paper blue

Tastes bitter

Slippery feel in water

Question 4

Native species may be wiped out in Bukit Timah Nature Reserve. The acidity of the streams in the nature reserve is more acidic as compared to 20 years ago. The population of certain animal species have decreased and crabs have developed harder shells.

Acid deposition originates both inside and outside of Singapore. Within Singapore, industrialisation and presence of aerosols cause acid deposition. Transboundary sources include forest fires from Indonesia. Forest fires produce carbon dioxide and sulphur dioxide, which combines with rain to make carbonic acid and sulphuric acid.

Posted on

Water for Life

YAY, its Wednesday again! cool Today, we learnt about water. We didn’t know that there are so many methods of water purification and the impacts of each method. In Singapore, we have limited water resources, so we should all do our part to save water as there is a water hike recently announced by the Budget. Anyway, these are our group’s answers for this week’s questions:

Question 1

We can purify by boiling, the use of water purification tablets, and the use of ultraviolet light water purifier.

Cost Effectiveness
Boiling Low Requires carrying of solid fuels and cooling down after boiling for it to be consumed
Water Purification Tablets Medium Tablets do not kill cryptosporidium (a form of microscopic parasite)
UV Light Water Purifier High Not effective when water has a lot of suspended solids

None of the methods used is similar. Municipal water supplies are treated extensively with many steps involved such as flocculation, fluoridation, ammoniation, and pH adjustment. On the other hand, the water purification methods used during hiking are simple. Municipal water supplies are treated with the intention for long term storage whereas instant purification methods are used for on the spot consumption.

Question 2

Desalination requires a lot of energy and it is cost ineffective to run them. In addition, the high consumption of energy raises concern about environmental issues such as carbon emissions. Marine life gets affected as well as some ocean creatures can be sucked into the plants, causing disruption to the food chain. Marine life also gets affected by plants discharging brine which increases the salinity of the oceans and extra steps have to been taken to ensure its safe disposal.

Question 3

a. One of the major source of lead in drinking water is caused by the corrosion of lead pipes or solder drinking fountains, and water tanks.
b. Research activities should not contribute to lead in drinking water as safeguards should be in placed for proper disposal of lead. Furthermore, most experiments have been redesigned to avoid the use of toxic metal ions completely.

Question 4

Only water-soluble vitamins are polar. They have more polar groups than non-polar, and will mix with polar water molecules. On the other hand, non-polar vitamins are fat soluble and have few or no polar groups. Thus, they blend with polar lipids, making them fat soluble.

Yay, it has ended.Recess week is coming up! WOOHOO!!! xD (Thank you prof laughing) bye!!!!!!!!

 

 

 

 

 

Posted on

Global Climate Change

YAY, its Wednesday again! cool Today, we learnt about global climate change. Me and my group members feel very strongly for this topic, we should all do our part to reduce global warming and protect the environment (+ the polar bear cry) Anyway, these are our group’s answers for this week’s questions:

Question 1

Even though the amount of energy emitted is more than what it receives, the atmosphere still retains much of the emitted energy due to greenhouse gases. In addition, the Earth itself produces heat energy from its own core.

Question 2

The statement is incorrect. Global warming is causing the climate to be warmer and climate is described as the average weather over a long period of time (e.g. 20 to 30 years). However, winter is only a condition of the atmosphere that exists over a short period of time (i.e. one year). Hence, the fact that winter occurs does not mean global warming is not happening.

Question 3 

The rotation of water molecules in the atmosphere interferes with the detection of intended objects. Hence, it defeats the purpose of the radar.

Question 4 

The most serious short-term problem for us will be air quality. This is especially true as we live in cities where there are factories around the industrial area. This may lead to serious air pollution which will ultimately cause health problems such as breathing difficulties or lung diseases. In the long run, the most serious long-term concern is likely to be global warming as our lifestyles are likely going to be affected it, such as the need to reduce the wastage of electricity. In addition, other consequences of global warming include loss of sea ice, accelerated sea level rise and longer, more intense heat waves. These effects may lead to natural disasters such as tsunami eccentric weather patterns. Due to the rising sea levels, lands of lower altitude may be submerged, hence reducing the amount of available land for usage.

Yay, it has ended. Looking forward to recess week because our favourite lecturer has so kindly given us an extra week of break! WOOHOO!!! xD (Thank you prof laughing) bye!!!!!!!!

Posted on

Energy From Combustion

My favourite module is here again, today we learnt about energy from combustion!! After learning so much, this is the questions given by our professor and I shall post them online!cool

Question  1

Endothermic processes absorb energy. The  net energy change is positive. Exothermic processes releases energy and the net energy change is negative.

(a) exothermic, as charcoal releases heat when it burns and heat is a form of energy.

(b) endothermic, as water molecules need energy to break their bonds. Energy is absorbed when bonds are broken.

(c) endothermic, solid is converted to liquid, and energy is absorbed to  break the bonds.

Question 2

In order to have a good explosion, a large amount energy should be released. The energy released is determined by the difference in bond strength between the products and reactants. Therefore, to have a big explosion, the bond strength of products should be much higher than the bond strength of the reactants.

Consider a natural gas (methane) explodes:

CH4 + 2O2 -> CO2 + 2H2O

This reaction gives out a very large amount of energy during the process. The bond strength of the products  is higher than that of the reactants .

Question 3

Temperature is the determines the direction of heat flow. Heat is energy which flows from a hotter to a colder object. Imagine putting a ice cube into a hot water, the temperature of the hot water is higher than that of the ice.  Therefore, heat energy is transfered from the hot water to the ice cube. This causes the temperature of hot water to fall and the temperature of the ice cube to rise. This would continue until both are of the same temperature.

The heat energy of an object is determined by the mass, temperature and specific heat capacity. Using an example to explain, imagine a large pot and a small bowl sitting on your dinning room table. Both are filled to the brim with hot soup of the same temperature. The small bowl of soup will reach room temperature faster than the big pot of soup despite the fact that they are of the same temperature. This is due to the difference in heat energy due to the differing masses of the big pot of soup and the small bowl of soup.

Question 4

a) an octane number of 98 means a knocking characteristic of 98% isooctane and 2% heptane.

b) the information given does not tell us anything about whether the fuel contains oxygenates.

That’s all for this week, can’t wait for next week 🙂

Posted on

Ozone is awesome.

CNY is finally over! All the goodies are making me fat.:( Anyways, finally i get to attend my favorite module CM8001! We learnt about ozone today!

Ozone is mostly found in the stratosphere and it does important job – protecting us from ultra violet radiation.  Ultra violet light excites electrons and breaks chemical bonds in our DNA causing skin cancer. (thank god for it i dont want to die)

We also learnt about the Chapman cycle which tells us there is a steady state for ozone which implies that the rate of formation and depletion of ozone is the same.

                   CFC

CFC is the main culprit that causing ozone to deplete. The chlorine in CFC acts as the catalyst in breaking down ozone. It was banned.