CHEMICAL BONDS

Chemical Bonds
I. Introduction Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms called a chemical bond. The two extreme cases of chemical bonds are the covalent bonds and ionic bonds. Covalent bonds are bonds in which one or more pairs of electrons are shared by two atoms. Covalent bonds, in which the sharing of the electron pair is unequal, with the electrons spending more time around the more non-metallic atom, are called polar covalent bonds. In such a bond there is a charge separation with one atom being slightly more positive and the other more negative, i.e., the bond will produce a dipole moment. On the other hand, Ionic bonds are bonds in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other. In the extreme case where one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond. Covalent bonding is a form of chemical bonding between two non-metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds. Ionic bond, also known as electrovalent bond is a type of bond formed from the electrostatic attraction between oppositely charged ions in a chemical compound. These kinds of bonds occur mainly between a metallic and a non-metallic atom. In Chemical Bonds, the principle “like dissolves like” is always abided.

To verify the above concept, an experiment was conducted with the following objectives: (1) identify ionic and covalent compounds based on certain physical properties, (2) differentiate between: a. covalent and ionic bonds b. nonpolar and ionic compounds c. polar and nonpolar compounds, (3) enumerate a few properties of: a. ionic compounds b. polar compounds c. nonpolar compounds, (4) explain why some compounds dissolve in water but others don’t, (5) predict the type of bond that may be present in an aggregate of atoms, given a set of properties.

II. Chemicals/ Reagents needed The chemicals and reagents used in the experiment are as follows: cupric chloride crystals (CuCl2), distilled water (H2O), kerosene, cooking oil, salt (NaCl) solution, alcohol, Salt (NaCl), and sugar. The apparatus used include test tubes, and two softdrink caps (tansan).

III. Procedure 1. Solubility 1.0 mL of water was placed in a test tube and 1.0 mL of kerosene in another test tube. After that, a piece of cupric chloride crystals was added in the two test tubes. Then it was shaken and we recorded the observed results. Afterwards, we then repeated the above procedure using cooking oil instead of cupric chloride crystals. And again, we recorded the observed results. 2. Relative boiling point We placed 5.0 mL of water in a test tube, NaCl solution in the second test tube, and alcohol in the third test tube. Then we heated the three test tubes simultaneously. And then, we recorded the time until boiling occurred.

3. Relative Melting Point First we placed a pinch of salt (NaCl) crystals in a softdrink cap (tansan) and about the same amount of sugar in another cap. Then we heated the two caps simultaneously on an alcohol lamp and we recorded the time for each solid to melt.

IV. Observation The results of the experiments for solubility, relative boiling point, and relative melting point are summarized in the tables below.
A. Solubility Test Tube | Substance Used | Description of the resulting mixture | Type of Primary Bond | | Solute | Solvent | | Solute | Solvent | 1 | CuCl2 | H2O | Soluble | Ionic | Polar | 2 | CuCl2 | kerosene | Insoluble | Ionic | Non-polar | 3 | Cooking Oil | H2O | Immiscible | Non-polar | Polar | 4 | Cooking Oil | kerosene | Miscible | Non-polar | Non-polar |

B. Relative Boiling Point Test Tube | Material Used | Boiling Temperature | Time needed to bring the substance to boiling | 1 | NaCl solution | - | 44.30s | 2 | Distilled H2O | - | 36.65s | 3 | alcohol | - | 29.05s |

C. Relative Melting Point Test Tube | Substance Used | Time needed to melt the substance | 1 | NaCl | After 5 minutes it did not melt | 2 | sugar | Before 5 minutes it melted |

V. Discussion of Results This experiment is all about Chemical Bonds. In the first two test tubes in the first table (Solubility), the result shows that when cupric chloride was added to water, it dissolved but when cupric chloride was added to kerosene, it did not dissolve. In other words, cupric chloride is soluble in water but is insoluble in kerosene. Since cupric chloride is an ionic compound, it will likely dissolve in water because water is a highly polar covalent compound and because of its charged nature, water is a very good solvent for ionic compounds. In the third and fourth test tubes, cooking oil and water is immiscible while cooking oil and kerosene is miscible. This is because we are following the principle “Like Dissolves Like” and we all know that cooking oil is non-polar and water is polar, so based on the principle “like dissolves like”, polar and non-polar will never mix. And, since cooking oil and kerosene are both non-polar, they will surely mix.

In the second table about Relative Boiling Point, it shows there that alcohol is the very first to boil and second is the distilled water, and then the third is the NaCl solution. Alcohol and distilled water are the first ones to boil because they are both covalent compounds and covalent compounds have low boiling point. In contrast, NaCl is the last to boil since NaCl is an ionic compound, and ionic compounds have high boiling point.

In the third table about Relative Melting Point, the results show that when the sugar was heated, it melted before five minutes; while on the other hand, the salt (NaCl) did not melt even after five minutes. Same in the relative boiling point, the sugar is a covalent compound that is why it has a low melting point and since NaCl is an ionic compound and has a high melting point; it is natural for it to not melt even after five minutes.

VI. Conclusion In conclusion ionic compounds usually form crystals, they have high melting and boiling points, they are also hard and brittle, and they usually dissolve in water. Ionic compounds are also good conductors of electricity when it is dissolved in water. And in contrary to that, covalent compounds usually form in solid, liquid or gas, they are poor conductors of electricity and they have low melting and boiling points. They also do not usually dissolve in water and are flammable. Covalent bonds can be easily broken into its primary structure as the atoms are close by to share the electrons. These are mostly gaseous and even a slight negative or positive charge at opposite ends of a covalent bond gives them molecular polarity. Covalent bonds are a weak bond. Ionic bonds conduct electricity in molten or solution state and they are extremely polar bonds. Most of them are soluble in water but insoluble in non-polar solvents. They require much more energy than covalent bond to break the bond between them. Ionic bonds are a strong bond. Non-polar molecular compounds are usually not soluble in water while ionic compounds are usually soluble in water. Non-polar compounds are, however, soluble in other non-polar solvents such as toluene and other organic solvents. Some properties of ionic compounds are hard, form crystal lattices not molecules, good insulators, have high melting points/ boiling points, and conduct electricity when dissolved in water or as a liquid. Non-polar compounds and those which are nearly non-polar are conductors of electricity also.