6.03 Chemistry Lab

Melting Point Data Table Compound Aspirin Caffeine Salicylamide Actual MP (ºC) 93 - 98 260 - 262 96 - 102 Expected MP (ºC) 135 236 140 Percent Error (%) ~30% ~12% ~30%

6-3: This process is used by cells to manufacture _biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products__

The main objective of this experiment is to differentiate between a physical change and a chemical change.

The purpose of this lab is to study some of the physical properties of two types of solids – ionic and molecular. The samples used are sodium chloride (ionic) and camphor (molecular). The physical properties studied are odour, hardness, melting point, solubility in water and solubility in 2-propanol. It is observed that some of the physical properties of sodium chloride are no odours, hard, a high melting point, soluble in water and insoluble in 2-propanol; some of the physical properties of camphor are a strong odour, soft, a low melting point, insoluble in water and soluble in 2-propanol. A few conclusions can be drawn from these

I will be doing this experiment to understand density of water compared to the volume of an object. D=m/v=mass/volume

Other substances that dissolve in water also lower the freezing point of the solution. The amount by which the freezing point is lowered depends only on the number of molecules dissolved, not on their chemical nature. This is an example of a colligative property. In this project, you'll investigate different substances to see how they affect the rate at which ice cubes melt. You'll test substances that dissolve in water (i.e., soluble substances), like salt and sugar, as well as substances that don't dissolve in water (i.e., insoluble substances), like sand and pepper. Which substances will speed up the melting of the ice?

pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.

3.6.1. BAP (Benzyl amino purine) stock solution (2mg/ml): 20mg of BAP being weighed and dissolved completely in 1N NaOH to a final total volume of 10 ml with autoclaved double distilled water to obtain a stock concentration of 2mg/ml was prepared and stored in clean autoclaved vials at -4°C.

Discussion: As seen in the melting point determination, the average melting point range of the product was 172.2-185.3ºC. The melting points of the possible products are listed as 101ºC for o-methoxybenzoic acid, 110ºC for m- methoxybenzoic acid, and 185ºC for p- methoxybenzoic acid. As the melting point of the sample

Solubility – Very soluble (water), Freely soluble (methylene chloride, chloroform, alcohol), Slightly soluble (acetone) and Insoluble (ether).6 Melting point - 120°C or 248°F.5

Magnesium Oxide has a very high melting and boiling point of 2852 and 3600 respectively. Magnesium oxide is held toghether with ionic bonds, and therefore require a lot on energy to separate the ions, and due to the strong electrostatic force of attraction between the ions, it makes the magnesium oxide less soluble.

Macromolecules have a large covalent structures which contain non-metal atoms, they are joined to contiguous atoms by covalent bonds. Substances that have giant covalent structures have high melting points due to a lot of strong covalent bonds that must be broken.

The overall purpose of this lab was to see how bonding effects chemical and physical properties. The lab consisted of 6 compounds Dodecanoic Acid, Sodium Chloride, Duodecose, Octadecanoic Acid, Potassium Bromide and Amylose. Using these compounds, tests were conducted on their appearance, solubility in distilled water, conductivity and melting point. There are 3 groups these compounds can be organized into. One group is Dodecanoic Acid and Stearic Acid. Another group is Duodecose and Amylose and the last group is Sodium Chloride and Potassium Bromide. These compounds are put into these groups because of their similar structures and properties.

The reason that the Table 2 “unknown sample #8” (maleic acid) shows a higher melting point than Table 2.1 is because the ramp rate was set to 10°C/ min. When the ramp rate is set to a higher number such as 10, the results will not be as accurate. That being said, it is best to set the DigiMelt to a lower ramp rate such as 2°C/ min. While setting the DigiMelt’s ramp rate to a lower dial will take longer, it will ensure that the melting point temperatures obtained are relatively accurate. Table 2.1 shows the results at 2°C/ min which gave the researchers more accurate results. Table 2.1 also shows that the 50/50 mixture of the two maleic acid samples melted at a lower temperature then the two maleic acids did on their own.This is because the researchers were mixing two different impurities together disrupting the compounds intermolecular forces, which ultimately caused the molecules to recrystallize and the melting point to decrease because the sample now has more impurities. The more impurities a sample has, the lower the melting point is.Being able to perform this technique using a DigiMelt is useful because it is an easy way to make sure that the sample

As mentioned in the discussion, olive oil, vegetable oil, crisco, and lard were soluble in nonpolar solvents and insoluble in polar solvents. This is due to the chemical composition of polar and nonpolar substances which results from the molecular shape as well as properties of dissolving solutes in solution. Polar substances are hydrophilic and contain polar Van Der Waals interactions (intermolecular forces) such as dipole-dipole forces, ion-dipole forces, and hydrogen bonding. Nonpolar substances are hydrophobic and contain non-polar Van Der Waals interactions. ‘Like dissolve like’ is the reason only polar solutes dissolve in polar solvents and why nonpolar solutes dissolve in nonpolar solvents. Molecules with similar polarity have similar intermolecular forces and therefore, can interact with each, or in this case dissolve9. Additionally, the solubility of a compound is determined by the length of the hydrocarbon chain. Long hydrocarbon chains such as the one found in oleic acid makes a compound more insoluble10. Therefore, since the lipids used in this experiment were hydrophobic substances and each lipid has long hydrocarbon chains, the results were consistent with the scientific literature and principles.