Yes, it is a concern because water is a greenhouse gas. Hence, it has the potential to cause global warming. Too much of it released in the atmosphere will lead to a greenhouse effect, causing environmental problems.

Fossil fuels are formed as a result of photosynthesis that took place millions of years ago. Solar energy is a necessary ingredient in the formation so the energy stored in chemical bonds in fossil fuels originally was from the sun.

Firstly, it requires a lot of energy to electrolyse water. Moreover, pure water is required for the process and this is hard to obtain especially since it is costly to purify water. Lastly, water is a precious resource that is scarce in certain regions. Hence, it might not be a viable means to obtain hydrogen.

a) C6(H2O)6
b) Refer to hardcopy
c) No. They have same structure but different chemical properties.

It is impossible to consume an entirely “chemical-free” diet as our body needs certain kinds of chemicals. And it is impossible to find food that does not contain or involve chemicals at all. Furthermore, organic food might not contain sufficient nutrients that our body require.

This is because acetone dissolves the polymer, allowing the gas of the foaming agent to escape. Since the gas is removed, the structure of the polymer is changed and the structure of the polymer becomes more dense.

(a) This is because LDPE does not have the required strength.

(b) Molecules of HDPE must line up in a way that gives the polymer strength. Moreover, using a thin linear HDPE allows sufficient flexibility.

3. No. This is because unlike plastic, paper is made of cellulose molecules that are held rigidly in place and are not free to be aligned. Hence, it will break when pulled. In contrast, in plastic, molecules can be aligned. This is because weak but extensive dispersion forces are present in plastic, allowing molecules to slip past one another.

(a) It has to be stable, durable, non-toxic and does not react with bodily fluids.

(b) Polymethyl methacrylate (PMMA) for rigid gas permeable lens and fluoro-silicone-acrylate/fluoro-silicones. The desirable properties would include being inexpensive, comfortable, non-toxic and oxygen permeable.

(c) As mentioned, hard contact lens are made of PMMA whereas soft lens are made of silicone. The difference lies in that silicone is flexible and allows oxygen to reach the eye and is hence more comfortable.

1. Number of neutrons and number of electrons
2. Number of protons, neutrons and electrons

14N means that the nitrogen isotope has 7 protons and 7 neutrons, while 15N means that the nitrogen isotope has 7 protons and 8 neutrons.

a. 94
b. 93 protons – neptunium
94 protons – plutonium
c. Radon-222 has 86 protons

E – fuel rods
D – cooling water into the core
B – cooling water out of the core
A – control rod assembly
C – control rods

Desalination is expensive, and uses large amounts of energy. Not only is this an inefficient allocation of resources, the environment will be negatively impacted as well, such as the increase in greenhouse gas emissions. Also, the natural habitat of marine life will be disturbed, thus affecting the ocean’s biodiversity.

Like dissolves like. Since water-soluble vitamins are soluble in water, a polar solvent, we can deduce them to be polar compounds. Likewise, since fat-soluble vitamins are soluble in non-polar solvents like fatty tissues, we can expect them to be non-polar compounds.

a. This reduces consumption of electricity that reduces the burning of fuel, releasing less sulphur/sulphur dioxide.
b. This reduces usage of vehicles, reducing combustion of fuel that will release less nitrogen/nitrogen dioxide.
c. This allows for more effective usage of energy, reducing unnecessary burning of fuel that thus releases less sulphur/sulphurs dioxide.
d. Less energy will be required to heat up the water/keep it heated, reducing electrical consumption and thus the amount of sulphur/sulphur dioxide released.
e. This cuts down the need for transportation (e.g airplanes) for imported food, reducing the energy used and thus the amount of nitrogen/nitrogen dioxide released.

All in all, the reduction in electrical consumption and need for transportation will reduce the amount of sulphur dioxide/nitrogen dioxide, that reduces production of acid rain.

a. Coal-fired plants produce soot when fossil fuels are burned.
b. The natural pH of rainfall is pH~5,6. Hence, if the pH is 10 times more acidic than natural, the estimated pH will be pH~4,5.

a. Exothermic- the reaction is a combustion process,in which heat is given out.
b. Endothermic- there is a gain in heat energy to break the bonds in water to form water vapor
c. Endothermic- heat energy is absorbed to break the bonds in the solid state

The bond strength of products are higher than that of the reactants. This results in a greater amount of energy needed to form the bonds. As such, the enthalpy of combustion is higher resulting in an exothermic reaction. Moreover, the products formed should be gases (rapid increase in volume) instead of solids or liquids leading to explosive reactions.

Temperature: is the direction of heat flow and measures the speed at which heat energy flows
Heat: Flow of energy from a hotter to a colder object
Example: A cube of ice placed on the hand of a man. Overtime, heat conducted from the man’s hand to the ice cube will cause it to melt.

a. The premium gasoline is made up 98% isooctane and 2% heptane. This implies that the gasoline has a relatively high octane rating, resulting in lower knocking characteristics.
b. Octane rating is insufficient to determine if the fuel contains oxygenates.