Substances & Their Characteristics

Qu. 2. Matter exists in three different forms: as a solid, a liquid, or a gas. In the solid state, the molecules of the matter are packed closely together, and the forces of attraction between the molecules overcome the forces of translational motion, so they do not move around (States, 2003). However, the do exhibit vibrational motion in the solid state. In the liquid state, the molecules are still closely packed, but not as closely packed as in the solid state, so they can move around. They do not have enough energy to leave the liquid state and become a gas under normal circumstances, except for a few fast-moving molecules which escape the liq

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e pressure increases (Sisler, VanderWerf and Davidson, 1967, 58). The quantity of heat required to vaporize a unit weight of a given liquid is called its heat of vaporization. It decreases with increases in temperature. Evaporation and vaporization involve a loss of energy by the liquid: as the faster, high-energy molecules escape, only the slower, low-energy ones are left behind, and so the liquid is cooled. Heat must be continually applied to keep the temperature constant. Qu. 3. An English chemist named John Dalton is considered the ôfatherö of modern atomic theory (Development, 2004). Dalton had four basic ideas on atomic theory: chemical elements are made up of atoms; the atoms of an element are identical in their masses; atoms of different elements have different masses; and atoms only combine in small, whole number ratios such as 1:1, 1:2, 2:3, etc. (Park, 2000). That elements are made up of atoms is still true, and has been known since the time of the Ancient Greeks. The second, idea, that all atoms of an element are identical has since been disproved, but the idea of isotopes was unknown in DaltonÆs time (1766-1844). The third idea, that atoms of different elements have different masses, was not new, but
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Approximate Word count = 3820
Approximate Pages = 15 (250 words per page)

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