David Ihim
Dr. Lowery
Pre-Ap Chemistry
30 November 2015
Don’t Flip Your Lid Research Paper Have you ever wondered why different elements have different melting and boiling points? Why some Molecules melt faster or take longer to boil? It all comes down to the forces and structure among the molecule. They are refer to as Chemical Bonding and Intermolecular or Intramolecular forces. The changes in states are due to changes in forces among the molecules rather than in those within the molecules (Zumdal 451). In this paper the effects of Chemical Bonding and Intramolecular Forces on the melting and boiling points of chemicals will be explained. These forces may involve covalent or ionic bonding, or they may involve weaker interactions usually
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The forces that exist among noble gas atoms and nonpolar molecules are called London dispersion forces (Zumdal 452). Dispersion forces are weak forces that result from temporary shifts in the density of electrons in electron cloud (Buthelezi et al. 412). Dispersion forces are named after the German-American physicist who first described them, Fritz London (Buthelezi et al. 411). The movement of electrons in the nucleus, develops a momentary non symmetrical electron distribution in noble gas atoms that creates dipolar arrangement charge for a short time. Electron distribution can occur due to the temporary formation of the dipole. That is, this instantaneous dipole that occurs accidentally in a given atom can then induce a similar dipole in a neighboring atom (Zumdal 453). The instantaneous dipole then goes to a short and weak interatomic attraction. But can be very significant for large atoms (Zumdal 453). Polarizability which indicates the ease with which the electron cloud of an atom can be distorted to give a dipolar charge (Zumdal 453). From this we can conclude large atoms that have many electrons will express a greater polarizability than small atoms. This means that the importance of London dispersion forces increases greatly as the size of the atom increases (Zumdal 453). So we can conclude molecules that do not have permanent dipole moment, their means of attracting each other is London dispersion forces. Remember that the electron in an electron cloud are in constant motion. When two molecules are in close contact especially when they collide, the electron cloud of one molecule repels the electron cloud of the other molecule, the electron density around each nucleus is, for a moment, greater in one region of each region of each clod, each molecule forms a temporary dipole when temporary dipoles are close together a weak dispersion
It was learned that changing the volume of the same substance will never change the boiling point of the substance. However having two different substances with the same volume will result in two different boiling points. The purpose of this lab was to determine if changing the volume of a substance will change the boiling point. This is useful to know in real life because if someone wanted to boil water to make pasta and did not know how much water to
Especially with big quantities of a substance, the melting point tends to be a range of values rather than just one value. This is because all the substance will not melt at once; it takes some time to melt at its estimated melting point. However, the hot plate will continue to increase the temperature, even when the substance is at its melting point. Thus, a more accurate range of temperatures will be acquired if the substance is heated slowly. 2.
2. What observation leads you to believe there is a force of attraction between water
Covalent and ionic are two forms of atomic bonds both of which differ in their structure and properties. Firstly, it should be made clear that an atom’s desire is to achieve stability. Most atoms by nature are not balanced electrically. They achieve balance by sharing or transferring their outermost energy level which contains electrons called valence electrons. The number of valence electrons in an atom mostly determines that atom’s or element’s properties.
The mass of 2mL of the solvent, p-xylene, was measured as well as the mass of 10 drops of toluene, the solute. The temperature of the solution rose to the freezing point after supercooling, then continued to drop as the solution froze, versus stabilizing as the pure p-xylene did. The maximum temperature obtained after supercooling was recorded as the freezing point of the solution. This process was repeated three times, each with a new test tube and the same beaker and scale for measuring the masses, then the Tf was calculated for each trial, as well as the average Kf. For the final portion of the lab, the same procedure as above was followed with the substation of 10 drops of unknown solutes instead of toluene in the p-xylene. Each unknown, A, C, and D, had one trial each. With the experimentally gathered data, the molar masses were then computed and compared to the given compound molar masses to
A molecule is a group of atoms that are bonded together. Some are covalently bonded and others are ionically bonded. For example, an organic compound is a compound that is covalently bonded(blue book). Because it is covalently bonded, it’s valence electrons are shared, instead of transferred, like an ionic bond. For examp...
When water molecules are close together, the regions that are positively and negatively charged are attracted to the oppositely charged regions or nearby molecules.
Atoms with higher electro negativity will pull the low electron negativity atom, but this will not happen in a diatomic molecule because their electro negativities will cancel each other.
Inc., J. W. (n.d.). The unusual Properties of Water Molecules . Retrieved from dummies : dummies.com
Van der walls forces are found between all atoms and molecules. This force is weaker than dipole-dipole and hydrogen bond forces, although, the larger molecules or atomic masses the bigger van der walls forces will be. Dipole-dipole forces occur between molecules that have a permanent net dipole, which means it attracts the forces between the positive end of one polar molecule to the negative end of another polar molecule. The strongest intermolecular force is the hydrogen bond, a relatively strong form of intermolecular attraction. A hydrogen bond occurs when an electronegativity atom with a pair of electrons is bonded to a hydrogen, a good example of that is water.
its state (Solid, liquid, gas); thus water has a higher melting point and a higher boiling
In particular, the forces exerted on a nucleus in a molecule by the other nuclei and by the electronic charge density may be rigorously calculated and interpreted in terms of classical electrostatics. Thus, given the molecular charge distribution, the stability of a chemical bond may be discussed in terms of the electrostatic requirement of achieving a zero force on the nuclei in the molecule. A chemical bond is the result of the accumulation of negative charge dens...
Covalent bonds can also be formed in such a way as to form a giant
Ionic compounds, when in the solid state, can be described as ionic lattices whose shapes are dictated by the need to place oppositely charged ions close to each other and similarly charged ions as far apart as possible. Though there is some structural diversity in ionic compounds, covalent compounds present us with a world of structural possibilities. From simple linear molecules like H2 to complex chains of atoms like butane (CH3CH2CH2CH3), covalent molecules can take on many shapes. To help decide which shape a polyatomic molecule might prefer we will use Valence Shell Electron Pair Repulsion theory (VSEPR). VSEPR states that electrons like to stay as far away from one another as possible to provide the lowest energy (i.e. most stable) structure for any bonding arrangement. In this way, VSEPR is a powerful tool for predicting the geometries of covalent molecules.
Another force, the weak nuclear force, without it life would be impossible. The weak nuclear force has a large responsibility for the radioactive decay of an atom. Without radioactive decay, radiation would be im...