Structural rearrangement: From expanded, when you add acetone IMF is removed. Therefore, molecules exist singularly. Then after acetone is evaporated, new molecules form a IMF therefore leading to a new structure.

a. It is not very strong – easy to tear
Crystalline structure of LDPE is amorphous. That makes the mechanical strength of the LDPE lower than HDPE which has a uniformly crystalline domain.

b. uniformly crystalline domain allows HDPE to be much stronger. Thus, much harder to tear.

Plastic is a LDPE which is a thermoplastic material. This means it allows molecules to slip past one another allowing the plastic to stretch and cause necking.
Paper is a form from cellulose that contains a hydroxyl group. It allows formation of hydrogen bonds with oxygen on the neighbouring chain. It holds the chain firmly which causes stiffness to increase.

a. high transparency
high chemical resistance
high resistance to lipids
very good stress-cracking resistance

b. PMMA (poly methyl methylcrylate) – Hard
PHEMA (poly hydroxylethylmothacrylate) – Soft
c. Soft contact lens are gel-like plastic made of PS. Hard contact lens are PMMA lens, these are firm and durable plastic. Soft contact lens are softer and much more moist. Thus it is easier to wear and much more comfortable.

Isotopes – 12C 13C 14C
Allotropes – Graphite Diamond Soot (Structural differences)

Carbon vs Uranium
They have different: Neutrons, Protons and electrons.

14N and 15N are isotopes of each other.
14N contains 8 protons and 6 neutrons while 15N contains 8 protons and 7 neutrons.

a. 94
b. 93 – Neptunium
94 – Plutonium
c. 86 Proton

A – Control Rod Assembly
B – Cooling water out of core
C – Control Rods
D – Cooling water into the core
E – Fuel Rods

Desalination is a costly process, and it is difficult to build. It requires expensive infrastructures. The by-product (brine) can destroy natural environments if contamination occurs. Lack of accessibility to sea water in landlocked countries, makes it limited to coastal areas.

Water soluble vitamins are expected to be polar compounds since like dissolves like. Water is a polar compound and for vitamin to be soluble, it has to be polar as well.

Fat is lipid, and lipids contain a hydrophobic tail and hydrophilic head, thus, fat soluble vitamins are expected to be non-polar to blend into the hydrophobic fats.

a. By hanging your laundry to dry, electronic dryer is not used, hence lesser electricity is used. Usage of lesser electricity, lower electricity consumption means lower fuel consumption, this will result in a lesser need for burning of coal for fuel.

b. There will be lesser use of personal vehical, means lesser auto mobiles on road, reducing pollution by cars.

c, d. Both reduced the amount of electricity required, conserving energy, reducing fuel consumption from power plants and thus lesser pollution from power plants.

e. By increasing locally grown production, the demand for imported produced food decreases hence decreasing factory outputs lowering pollution from factory.

a. Coal fired plants produce electricity by burning coal in a boiler to produce steam. The steam produced, under tremendous pressure, flows into a turbine, which spins a generator to create electricity. While burning coal, incomplete combustion may happen, this will result in production of soot, carbon monoxide and many other harmful gases. This causes higher possibility of haze.

b. 5.3 (natural) 4.3 (estimated)

a. Exothermic. Combustion is an exothermic process, heat is released.
b. Endothermic. Heat energy is required to break some H-bonds for change of state from liquid to gas.
c. Endothermic. Heat energy is required to break some H-bonds to change from solid to liquid state.

Bond strength in reactants are weaker than that in products. Reactants undergo bond breaking which is endothermic (energy absorbed). Products undergo bond making which is exothermic (change in H < 0). As such, since net change in heat is negative (exothermic), bond strength of products are stronger.

Heat is the energy that flows from a hotter to a colder object. Temperature determines the direction of heat flow. Heat is a consequence of motion at the molecular level;
temperature is a measure of the average speed of that motion.

a. Octane number of 98 means a knocking characteristic of 98%
isooctane and 2% heptane. Knocking is premature ignition.
b. No, oxygenates are compounds which contain oxygen in their chemical structures, however, isooctane and heptanes are hydrocarbons.