Week 5: Concentrate to Hydrate

Lecture

In this week’s lecture, we discussed the results of the experiments from the past two weeks and reviewed the importance of safety while conducting our experiments as this is integral to designing and carrying out accurate experiments. The focus of this week’s experiment was determining how the ratio solid to liquid affects the concentration of the coffee. This was our third solid-liquid extraction.

A big part of lecture also centered around our midterm presentation in week six. We were instructed to create a 10-15 minute presentation that would be delivered in front of the class. The goal of the presentation is to share our thought process behind our project design as well as our results and any challenges we have faced along the way. The presentation will show our professors the progress we have made and will allow other groups to compare their experimental results to ours.

Planning

In order to determine how solid to liquid ratio affects the concentration of coffee, we decided to do a 1:1, 1:2, and 2:1 ratio. We kept the other steps from the previous weeks’ experiments the same, but decided to do three trials with 20g coffee to 20g water, 40g coffee to 20g water, and 20g coffee to 40g water. The temperature of the water would remain constant at 68ºC and the particle size would be medium/coarse.

We also began to discuss our midterm presentation. We decided our group would “present our findings from the experiments that we have conducted, our process flow diagrams, and the difficulties that we have [had]” (Week 5 Project Update Sheet). The most interesting part of our presentation will be the aspects about the challenges we have encountered and the advice we will provide to groups that may go through the same thing. The biggest takeaway for our audience would be the fact that it is entirely possible to conduct safe, accurate laboratory experiments outside of a laboratory setting.

Laboratory

While performing this week’s experiment, I ran into some issues. It quickly became apparent that the ratios between coffee grounds and water would not allow us to achieve accurate results. This was because 20g of water just was not enough to saturate the coffee grounds for even 30 seconds, let alone four minutes. I let the group know of the trouble I was having, and we decided to alter our ratios: 20g coffee to one cup water, 40g coffee to one cup water, and 20g coffee to two cups water. By changing the experiment in this way, I was able to obtain multiple accurate data points.

I began the experiment by grinding 20g of coffee to a coarse grind and placing it in the filter paper inside the cone. I heated up one cup of water to 68ºC then poured it over the coffee grounds once it reached temperature. I let the coffee steep for four minutes, taking one sample every 30 seconds. After the four minutes were up, I repeated the process with 40g coffee and one cup of water, then again with 20g of coffee and two cups of water. Once all three trials were completed, I let the samples cool to room temperature before taking the conductivity of each sample three times and recording it.

After obtaining conductivity values for each sample, I measured the volume of coffee made from each trial. I then created tables of my data and calculated the average conductivity values and corresponding concentrations. From the average concentration and total volume of each trial, I calculated the number of grams of coffee which that was made. I also graphed the relationship between time and concentration for each of the trials.

As you can see from Figure 1, Series 3 had the highest concentration values, which means that less water and more coffee grounds will give you a more concentrated cup of coffee. The second highest was Series 1 and the lowest was Series 2. This makes sense because it shows how more water than coffee grounds will give you a more diluted cup of coffee. In terms of the final masses of coffee, Series 3 had the most with 11.13g. Series 2 had the next highest with 9.13g, and Series 1 had the least with only 6.26g.