a) They can have different number of neutrons and different number of electrons.
b) Different number of : 1) protons 2)neutrons 3)electrons

They are isotopes of N. 14N has atomic mass of 14 while 15N has atomic mass of 15.

a) 94 protons
b) Neptunium (93), plutonium (94)
c) 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 requires large amount of energy.
-It is expensive.
-It produces saline brine as residue.
-The process can be complicated.

-Water soluble vitamins are polar compounds. They have polar groups and hence are able to dissolve in polar solvent such as water.
-Fat-soluble vitamins are non-polar compounds. They are soluble in non-polar solvents such as fatty tissue in the body. Fat-soluble vitamins are predominantly non-polar.

Generating electricity from sources such as coal will produce sulfur oxides, which can cause acid rain. Using transportation vehicles can generate sulfur oxides and nitrogen oxides, which can also cause acid rain.

a)Reduce the use of electrical dryer, hence reduce electrical consumption.
b)Reduce the use of private transportation, hence reducing SO2 and NO2 emission.
c)Reduce electrical consumption.
d)Reduce heat loss from the heaters and pipes, hence reducing electrical consumption for heat generation.
e)Less transportation is needed to transport food from one country to another.

a) Coal-fired plants will produce and emit pollutants such as soot, which reduces visibility in the vicinity of the plant.

b) A 10 times increase in acidity translate to a decrease in pH of 1. Since the pH of natural rain is around 5.6, the pH of the rainfall in the park is estimated to be 4.6.

a) Exothermic – Burning releases energy in the form of heat.

b) Endothermic – Water absorbs heat energy before evaporation occurs.

c) Endothermic – Ice absorbs heat energy, this will cause the ice to melt into liquid due to the rise in temperature. This breaks the intermolecular forces of attraction, such as hydrogen bonding and van der waals, between water molecules.

The reactants will have lower bond strength, whereas the products will have higher bond strength, in order for an exothermic reaction to occur.

Heat is energy that flows from a hotter to a colder region, whereas temperature determines the direction of heat flow. Heat is due to the motion of molecules while temperature is a measure of the average speed of the motion.

a) It has similar knocking resistance as octane.

b) The higher the concentration of oxygenates in the fuel, the higher the octane ratings, which will allow the engine to run more smoothly.