Determine Unknowns

After each of the solids were completely dry, each was placed into a MelTemp device. The temperature at which each solid began to melt and completed melting was recorded.

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

Chemical changes are often accompanied by physical changes. Three that you should not see in this lab are changes in temperature, presence of a flame, and evolution of light, as when as firefly glows. Three physical changes that indicate a chemical change may have occurred (and that may be seen in this lab) are:

Melting range would be closely related to a mixed sample whose constituents are most identical. In other words, melting point will have a wide range and would be below 200°C and above 95°C.

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

Purpose/Introduction: The objective of this lab was to recognize and differentiate between physical and chemical changes in matter. Physical change can be defined as a usually reversible change from one state (solid, liquid, or gas) to another without a change in chemical composition. The physical properties of a substance--such as size, shape, density, or state--are altered. An example of a physical change is ripping paper.

The purpose of this experiment is to identify an unknown substance by measuring the density and boiling point. I will be able to conclude which substance is my own from a list of known options stating what its real boiling point and density is.

Objective: The objective of this experiment was to discover the specific heat of an unknown metal. By heating a metal then placing it in a calorimeter and taking the temperature of the solution as the heat transfer from the metal to the solution. This is done using a calorimeter, thermometer, 2 200mm test tube, an unknown metal, hot plate, 2 50ml graduated cylinders, sodium hydroxide, and hydrochloric acid. The techniques that are used in this experiment is cleaning glassware, disposing of chemicals, measuring mass, transferring solids, transferring liquids and solutions, heating liquids and solutions, and measuring the volume of solutions by examining the meniscus. Introduction: Chemical reactions always exerts some form of thermal energy, that energy then applies changes to its reactants, this is called Calorimetry which is the analysis of temperature change or heat change within a chemical reaction.

The purpose of the experiment was to determine the molar mass of three unknown solutes by measuring the freezing point depression of a solution containing each of the unknowns. When a solute is dissolved in a solvent, the vapor pressure of the solvent is lowered. As a result of the decrease in the vapor pressure, the colligative properties change.

Substances differs from each other as each of the substances have different atomic composition and structures. And although the substances that shares the same characteristic can be grouped together, each of the substances still have their own unique and defining physical and chemical properties. Therefore, some substances may undergo a chemical change while others don’t during a same reaction. In the experiment conducted, two different elements were used, Iodine crystals, I2 and Copper wire, Cu. After recording the initial observation on both of the elements, they were both heated and allowed to cool.

Colligative properties, such as boiling point and freezing point, are dependent on the amount of solutes added, not necessarily their identities (LibreTexts, 2018). A fascinating concept related to freezing points is Supercooling. Supercooling is a state where liquids do not form ice even when they reach temperatures below their normal freezing point; they are trapped in a metastable state (Esrf.eu, 2018). The best example of this is clouds at high altitudes: they contain tiny droplets of water that do not have seed crystals, and therefore do not form ice despite the low temperatures (Esrf.eu, 2018). The concept of freezing point depression is applicable in many parts of everyday life.

I was instructed to record a melting point range for each compound, rather than a single temperature melting point. The reason for this instruction is that polymers and unpure substance melt over a range of several degrees. Based on the melting point ranges for both substances, it is difficult to differentiate the two based on its melting point data alone. The ranges of the substances are close enough to one another that one could argue for experimental error when presenting the data as a solo identifying property.

The purpose of this lab was to study colligative properties. These properties are properties that are affected when a solute is added to a solvent. Thus, the amount is important, not the actual type of substance, for the colligative properties. A couple types of this property are the freezing point and boiling point of a substance. (1)

The boiling points of the more purified substances collected in a flask will be measure and categorized into a pure compound.

Brittain, C. G. (2009). Using Melting Point to Determine Purity of Crystalline Solids. Retrieved from http://www.chm.uri.edu/mmcgregor/chm228/use_of_melting_point_apparatus.pdf