1. Styrofoam contains mostly air hence when it is released by dissolving it in acetone, it looks like the huge quantity of solid is dissolved into a smaller quantity of liquid and is more dense.

2a. LDPE is soft, stretchy and flexible. It will not be resistant to cuts.

2b. It is successful in this application as a thin layer of HDPE was used. This allows the gloves to be less rigid and more flexible. At the same time, HDPE is also orderly arranged, hence maintaining the strength and resistance to being cut.

3. This does not happen in paper. When the plastic is stretched, the 3D structure is altered whereby the molecules become aligned and move in the direction of the pull. This is because there are weak dispersion forces between the HDPE molecules and are easier to break.
On the contrary, paper tears when it is pulled. This is due to the cellulose molecules having stronger intermolecular forces of attraction between the molecules hence it is difficult for molecule to slip pass one another.

3a. It should be safe, biocompatible, cost effective and long lasting.

3b. Polymers such as polymethyl methacrylate (PMMA) are used. More commonly now is the use of Silicone-acrylate materials under trade names such as Kolfocon. Lenses that are comfortable, safe, inexpensive and permeable to oxygen are a few desirable properties.

3c. The difference is that in hard contact lenses, PMMA is used. It is a rigid non permeable plastic. In soft contact lenses, silicone is used. Silicone is more flexible and comfortable to the user during long hours of wear. Silicone also allows oxygen to reach the eye hence it is healthier and safer compared to PMMA.

1a. Sulfate particles formed from sulfur dioxide which is produced by the coal fired plants. This results in the poor visibility.

1b. Normal rain is about pH5.3, since it is 10 times more acidic than natural, the rainfall in the park will have a pH of 4.3.

2a. By hanging it to dry, a dryer does not have to be used. This saves more electricity which is generated by burning of fossil fuels (in the US). With less burning of fossil fuels, less pollutants are produced and present in the atmosphere hence reducing acid rain.

2b. By taking public transport, less cars are used. This reduces emission of NOx and thus reduces the formation of acid rain.

2c. This is to save electricity as the machines will be used less frequently.  Electricity is generated by the burning of fossil fuels. With less burning of fossil fuels, less pollutants are produced and present in the atmosphere hence reducing acid rain.

2d. By insulating the pipes and heaters, we reduced the heat loss to environment. This decreases the amount of energy required to maintain the heat hence saving electricity by using fossil fuels. Burning of fossil fuels contribute to the formation of acid rain.

2e. By buying local food, our carbon footprint is reduced. This results in lesser pollutants formed and hence reduction of acid rain.

3a. Hydrochloric acid, HCl ; nitric acid, HNO3 ; sulfuric acid, H2SO4; carbonate acid, H2CO3 ; Phosphoric acid, H3PO4

sodium hydroxide, NaOH ; lithium hydroxide, LiOH ; magnesium hydroxide, Mg(OH)2; potassium hydroxide, KOH ; ammonia, NH3

3b. Acids are sour while bases are bitter. Acid turns blue litmus red while base turns red litmus blue. Both reacts with metals.

4. Some issues found in Singapore are the formation of acid rain and production of haze. Some examples are the corrosion of the National Museum of Singapore. Native species in Singapore including frogs, crabs and fishes may be wiped out by the acid rain. The haze is caused by the burning of biomass in neighbouring countries hence the acid deposition originates mostly from outside Singapore’s borders. Some acid deposition also originates from inside Singapore’s borders as pollutants are produced by automobiles and factories.