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Periodical Maniacs 9/30/2011 Higginbotham


 * Lab 1: Determining Melting Points of 3,4-dimethoxybenzaldehyde and 1-indanone **

Purpose: to compare substances 3,4-dimethoxybenzaldehyde and 1-indanone in relation to their melting point ranges separately and when combined. Determine melting point of different ratios of urea and cinnamic acid compared to a pure urea sample. sentence fragment Members of the lab group hypothesized that the melting point would be greater than both individual melting points combined. When the chemical reaction with catalyst NaOH was performed, the melting point increased beyond individual melting points of 3,4-dimethoxybenzaldehyde and 1-indanone added together. That range was 142.3-156.0 degrees Celsius. The introduction is not a summary, and should not include data or conclusions reached after lab. Use this paragraph to explain the motivation for the lab and to discuss concepts that are related to the experiment.
 * INTRODUCTION:**

**PROCEDURE:**
 * 1) **Measure the melting point** of one of these compounds, as assigned: 1-indanone or 3,4-dimethoxybenzaldehyde. Repeat the melting point determination 3 times, each time allowing a different person in your group to watch the melting occur. Record your results on the chalkboard at the front of the room.
 * 2) Weigh out 0.20 g 1-indanone and 0.25 g 3,4-dimethoxybenzaldehyde. Take the chemicals back to the working area for later use.
 * 3) **In large group discussion** we will talk about **precision** in melting point data, and will make predictions about what might happen to melting points when two substances are mixed together.
 * 4) After the class predictions have been listed, place the two substances in the bottom of a small beaker. Crush and mix them thoroughly, using a glass stir rod or the back of a spatula. Complete mixing may take several minutes. Record any relevant observations.
 * 5) Add approximately 0.05 g (which is just about the size of the head of a pin) of powdered NaOH to the beaker and mix thoroughly for about 5 minutes. Allow the mixture to stand for an additional 10 minutes.
 * 6) Add about 2 mL of 10% HCl to the beaker. Test the pH of the resultant mixture by dipping the end of a glass rod into the mix and then touching it to a piece of pH paper. If the solution is not acidic, add 1 mL HCl and test again. Collect the solid product by vacuum filtration, using the aspirator to draw liquid through the filter. Dry the solid in a drying oven for 15 minutes, then test the melting point of the dry substance. (Note, let the sample air dry for approximately 15 minutes instead of the drying oven.)
 * 7) While waiting for the sample to air dry. Test the melting points of (a) pure urea, and (b) urea with cinnamic acid in any two ratios of the following: 1:5, 2:5, 1:1, 5:2, 5:1.

Here is the completed reaction between 3,4-dimethoxybenzaldehyde and 1-indanone with NaOH acting as a catalyst going to a product.


 * DATA:**

**Substance assigned for measurement** : 3,4-dimethoxybenzaldehyde


 * Trial 1**: Starting Power 25%, very slow heating so power was increased to 30%. Once the temperature hit 42.0 degrees C, there was constant sweating. Within 30 seconds the sample had completely evaporated. Temperature was at 43.0 C. Range: 42.0-43.0 degrees C.


 * Trial 2**: Was started at a lower starting power because the sample in trial one evaporated rapidly. Starting power was 20% and the sample was placed in the Mel-temp at 36.2 degrees C. It started sweating at 42.0 degrees Celsius and at 43.4 degrees C the sample had completely melted. Range: 42.0-43.4 degrees C.

The class reported every collected data on the board. The Mean for the melting point range temperature for 3,4-dimethoxybenzaldehyde was 43.0 degrees Celsius. For the 1-indanone the melting average temperature was 32. The instructions for step 3 was to make a prediction of what would happen to the Melting Point if both substances were mixed together. This data would be better represented with a table.

Four **HYPOTHESIS** were established by 4 different members of the afternoon lab. Hypothesis #1: Once the two substances are mixed together, the MP will be as low as 30 degrees Celsius. Hypothesis #2: Once the two substances are mixed together, the MP will be the average between the 2 substances, approximately 37 degrees Celsius. Hypothesis #3: Once the two substances are mixed together, the MP will rise to a temperature of roughly 60 degrees Celsius. Hypothesis #4: Once the two substances are mixed together, the MP will increase to 74 degrees Celsius

**OBSERVATIONS:**

During Step 4: As the two chemicals were mixed, they started to melt. How much was weighed out? It could have been a reaction or it could have shown that the melting point was quite close to room temperature. The mixing substance turned from a dry, white opaque crystallized powder to a clear amber liquid. Both substances indicated melting.

During Step 5: The liquid shot off a sweet aroma during the 5 minutes of mixing. Liquid changed from clear amber to a muddy green. After 10 minutes the sample turned darker green and became viscous. 2mL of 10% HCl was added to the mixture, it caused the sample to separate like oil and water and to turn yellow. The PH was tested and it was very acidic, approximately 1.

**Note: This part of the experiment became nullified, possibly due to adding the HCL too early and/or not adding enough NaOH.** (*Failed to check in with the professor before addeding the HCl. The sample needed more NaOH and was too oily. It was questionable whether or not it would separate in the aspirator (through a buchner funnel). The substance appeared to never have solidified. After observing the first filtration, it was apparent that the substance was too watery and the experiment needed to be repeated. After Repeating step 5, Approximately 3 times the amount of NaOH was added to the 50ml beaker. After 5 minutes the mixture was quite opaque and bright green. It continued to thicken to a buttery yellow paste. After the HCl was added, the PH was 1. The substance was added to the aspirator and sat to dry. During the air drying process, the melting point of pure urea was tested. The other ratios tested was 5 parts urea to 1 part cinnamic acid 5:1 and 1 part urea and 1 part cinnamic acid 1:1.

The dried sample was put into the Mel-temp apparatus and the starting power was set to 60%. The sample started sweating at 142.3 degrees C and was melted completely at 156.0 degrees C. Range: 142.3-156.0 degrees Celsius.

Pure: Start power was 20%. With a inclination of a higher MP, power was raised to 50% to increase the temperature faster. At 128 degrees Celsius, we lowered the Mel-temp power level to 40%. Pure Urea started sweating at 131.8 degrees Celsius and was completely melted by 133.2. Range: 131.8-133.2 degrees Celsius.
 * UREA EXPERIMENT:**

1:1 Ratio of Urea to cinnamic acid Start power at 20% and 58.6 degrees Celsius. Power was raised to 30%. Substance started sweating at 99.4 degrees Celsius and was completely melted at 103.2. Range: 99.4-103.2 degrees Celsius.

5:1 Ratio Starting power was 30%. Substance started sweating at 100.6 degrees Celsius and was completely melted by 106.5 degrees Celsius. Range: 100.6-106.5 degrees Celsius.


 * =  || Starts Sweating (Degrees Celsius) || Melted (Degrees Celsius) || Range (Degree Celsius) ||
 * Pure urea || 131.8 || 133.2 || 131.8-133.2 ||
 * 5 urea : 1 cinnamic acid || 100.6 || 106.5 || 100.6- 106.5 ||
 * 1 urea : 1 cinnamic acid || 99.4 || 103.2 || 99.4-103.2 ||

The y-axis is in degrees Celsius and the x-axis is the ratios of the pure urea to cinnamic acid. Where the blue on the graph represents the degrees Celsius at which the sample was completely melted. Did you try to show the ranges in your graph? They are an important part of the story.

**CONCLUSION:** Based on the results from the 3,4-dimethoxybenzaldehyde where the melting point average was 43.0 degrees Celsius and the 1-indanone melting point average was 32.0 degrees Celsius. The results of mixing the two together showed that the melting point was reduced to approximately room temperature in comparison to the original substances. When 3,4-dimethoxybenzaldehyde and 1-indanone were mixed together the substances melted immediately; then after adding NaOH the product became a paste like substance; the after adding HCL syntax: always use a lower case letter for the second letter of an elemental symbol) it was clear that the solid could be removed. The melting point was testing and found that the product's new melting point was 142.3-156.0 degrees Celsius. The results were different for the urea. The more diluted the urea was with the cinnamic acid, the lower the melting temperature was.

I also want you to discuss melting temperature ranges. What do they mean? And how does your data fit your expectations surrounding this issue?

**SOURCES OF ERROR:** NaOH is hydroscopic. The water absorbed could have offset the weight making the amount measured inaccurate for the experiment. The MP of a random amount of the substance was measured in the capillary tube. There could have been more sample in one capillary tube that another trial of the same substance. Which in turn would cause the Melting Point of the sample to increase from the standard. sentence fragment When the 3,4-dimethoxybenzaldehyde and 1-indanone were mixed together there may have been more of one than the other, possibly presenting a wide variety of melting points.


 * WORKS CITED: **

Higginbotham, Carol. "Melting Point Procedure." // BlackBoard Learn //. N.p., n.d. Web. 7 Oct 2011. .

Thompson, J. E. //Melting Point Study of a Solventless Reaction //, Science Division, Lane Community College, **2008 **