4.1 To separate a mixture of flour, sugar, and salt, first place the mixture in a container of water and stir gently. The salt and sugar will dissolve, but the flour will float, and can be scooped off the surface of the water and dried. Next, evaporate the water so that the sugar and salt will become recrystallized (General, 2004). Next, the sugar and salt can be separated by filtration through a fine sieve because salt crystals are much smaller than sugar crystals. The property of flour which us exploited is its organic nature. Flour is an organic compound and is soluble most readily in organic solvents, not aqueous ones. Sugar and salt both dissolve readily in water because they are both ionic compounds, and they can be crystallized out of solution by heating to evaporate the water. Because they differ in the size of their individual crystals, they can be separated on the basis of their crystal size by filtration. This separation exploits their crystal size and their ionic structure.
5.1 Isotopes are atoms of elements that have different numbers of neutrons (Science, 2000). For example, the most common isotope of hydrogen has no neutrons, but there is an isotope of hydrogen which has one neutron, and it is called deuterium. Another isotope of hydrogen has two neutrons and it is called tritium. Each atom has a preferred number of neutrons and protons, which is the number at which the forces holding the the nuclei together balance the best. The lighter elements tend to have as many neutrons as protons, whereas the heavy elements have more neutrons than protons. There can be isotopes which have two few neutrons or too many neutrons, but they do not last for long because they are unstable. These unstable atoms are radioactive, and their nuclide change (decay) by spitting out radiation in the form of particles or electromagnetic waves.
The isotopes are the same in that they are all composed of the same element, hy...