tag:blogger.com,1999:blog-14716910841980807712024-03-19T06:48:32.845-05:00Dr. Bodwin's Science of Cooking BlogThe science behind food and its preparation.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.comBlogger28125tag:blogger.com,1999:blog-1471691084198080771.post-26450192906204608282015-11-11T20:45:00.000-06:002015-11-11T20:45:59.905-06:00Heat Capacity (for people who prefer formulas and algebra)Heat capacity problems are always interesting because they are one of the types of science problems that you can often work through with just a little bit of insight into what heat capacity is, even if you don't know the "correct" way to do the problem. Heat capacity is the energy required to change the temperature of a substance. If you can keep track of energy, amount of the substance, and the temperatures before and after the change, you just might be able to cobble together the quantities and arrive at the right answer.<br />
<br />
But I know, sometimes you just want to memorize a mathematical formula and plug numbers in. If that's what you're looking for, then this is just for you. Heat capacity problems can pretty much all be solved using the formula:<br />
<div style="text-align: center;">
(Energy transferred) = (Heat capacity) x (Amount of substance) x [(Final temperature) - (Initial temperature)]</div>
Or, if we want to make that shorter:<br />
<div style="text-align: center;">
E = (C<sub>p</sub>) x (g) x (T<sub>final</sub> - T<sub>initial</sub>)</div>
Let's plug in information from 2 different problems:<br />
<br />
1. A 250.0g sample of water (C<sub>p</sub> = 1 <sup>calorie</sup>/<sub>(g)(<span style="background-color: #f9f9f9; color: #333333; font-family: "open sans" , "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; line-height: 20px;">°</span>C)</sub>) is heated from 14.3<span style="background-color: #f9f9f9; color: #333333; font-family: "open sans" , "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; line-height: 20px;">°</span>C to 27.4<span style="background-color: #f9f9f9; color: #333333; font-family: "open sans" , "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; line-height: 20px;">°</span>C. How many calories of heat energy have been transferred?<br />
Plugging in to the formula:<br />
<div style="text-align: center;">
E = (1 <sup>calorie</sup>/<sub>(g)(<span style="background-color: #f9f9f9; color: #333333; font-family: "open sans" , "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; line-height: 20px;">°</span>C)</sub>) (250.0g) (27.4<span style="background-color: #f9f9f9; color: #333333; font-family: 'open sans', 'helvetica neue', helvetica, arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C - 14.3<span style="background-color: #f9f9f9; color: #333333; font-family: 'open sans', 'helvetica neue', helvetica, arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C) = 3275calories</div>
<br />
2. A 400.0g sample of water is initially at 16.8<span style="background-color: #f9f9f9; color: #333333; font-family: 'open sans', 'helvetica neue', helvetica, arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C. If 5000 calories of energy is added to the water, what is the final temperature?<br />
Plugging in again:<br />
<div style="text-align: center;">
5000 calories = (1 <sup>calorie</sup>/<sub>(g)(<span style="background-color: #f9f9f9; color: #333333; font-family: "open sans" , "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; line-height: 20px;">°</span>C)</sub>) (400.0g) (<span style="text-align: center;">T</span><sub style="text-align: center;">final</sub><span style="text-align: center;"> </span>- 16.8<span style="background-color: #f9f9f9; color: #333333; font-family: 'open sans', 'helvetica neue', helvetica, arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C)</div>
Same thing, but now we have to do a little algebra to solve for <span style="text-align: center;">T</span><sub style="text-align: center;">final</sub>, and we get a final temperature of 29.3<span style="background-color: #f9f9f9; color: #333333; font-family: 'open sans', 'helvetica neue', helvetica, arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C.<br />
<br />
If you prefer a more descriptive solution to heat capacity problems, take a look at <a href="http://scienceofcooking100.blogspot.com/2015/11/heat-capacity.html">http://scienceofcooking100.blogspot.com/2015/11/heat-capacity.html</a><br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-28839651110014199492015-11-05T12:12:00.000-06:002015-11-05T12:12:12.499-06:00Heat CapacityThere have been a few questions about heat capacity…<br />
<br />
Heat capacity is a measure of the amount of heat required to change the temperature of a given amount of a substance by some amount. A common unit for heat capacity is "calories / (gram)(<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C)". For water, heat capacity is 1 calorie / (gram)(<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C), so if I have 1 gram of water and I want to increase its temperature by 1<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C, I have to add 1 calorie of energy to the water. What if I have more than 1 gram or I want to increase the temperature by more than 1<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C? Multiply!<br />
<br />
The reverse of this problem is really the same problem, it just requires some different math. What if I have 18.00mL of water that is initially at 12.6<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C and I add 49calories of energy to that water? First part… the density of pure water is 1 g/mL so 18.00mL of water has a mass of 18.00g. Now, if the heat capacity of water is 1 calorie / (gram)(<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C), and we have 18.00g of water, we can again multiply to get:<br />
<div style="text-align: center;">
{1 calorie / (gram)(<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C)} x 18.00g = 18.00 calories per <span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C</div>
So for every 18.00 calories of energy we add to <i>this specific sample</i>, we will increase the temperature by 1<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C. We are adding 49 calories to <i>this specific sample</i> so:<br />
<div style="text-align: center;">
49 calories / 18.00 calories per <span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C = 2.7<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C</div>
This is how much the temperature <i style="font-weight: bold;">changes</i> when we add this amount of energy. Since the sample was initially at 12.6<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C and we <i>added</i> energy, the new final temperature must be 2.7<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C <i>higher</i> than the initial temperature, 12.6<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C + 2.7<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C = 15.3<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C.<br />
<br />
There are some assumptions in this description (like the density of water) that simplify the problem… if you want to get the absolutely perfectly correct answer, you'd have to take some of those assumption into account, but this is close enough for our purposes.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-65089376790695236502015-11-02T11:30:00.000-06:002015-11-02T11:30:10.779-06:00Microwave Heating Experiment (Fall 2015)There are quite a few questions about the Microwave Heating experiment (<a href="http://www.drbodwin.com/teaching/scicook/bcbt100cEXPmicrowave.docx" target="_blank">procedure here</a>), so let me try to address them all in one place.<br />
<br />
The most common and persistent questions are related to the data analysis. The hands-on procedure and <i>collection</i> of the data seems to be going well, so let's not dwell on that part of the experiment. Once you have collected your data, you'll have a sea of numbers that you, as a scientific investigator, will have to process and interpret so you can get some useful information out of your experiment. The data you are collecting will look something like this:<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEittJKbUWwf_KfpK10jftkyaDdRVTqx893rP8uaMjBnmopi8uwIle-DyHaVEDclClaWMw8BAQhpR0SxtaT3SxE8DDd56jZZ5hptdek3_hzPr5tx0oYPbJG4Tuue_FyWQvxNruQOiC5fplQ/s1600/20151102data1.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEittJKbUWwf_KfpK10jftkyaDdRVTqx893rP8uaMjBnmopi8uwIle-DyHaVEDclClaWMw8BAQhpR0SxtaT3SxE8DDd56jZZ5hptdek3_hzPr5tx0oYPbJG4Tuue_FyWQvxNruQOiC5fplQ/s320/20151102data1.PNG" width="155" /></a></div>
The procedure tells you to prepare a graph of this data. Whenever you are collecting data (or just observing something interesting in your daily life) where one variable is under your control (in the case of this specific example, time), and another variable is simply a quantity you are measuring (in this case, temperature), it is ALWAYS interesting to consider what the graph of that information looks like. In this case, the graph of the above data looks like:<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnR_59E-9XxyI4O-pUUYJWfmJ3hkbWTt7Q3K9Bzt7TPigCjhsqQQeF9MdvDoWiGFKUcDtdEhEswKpTuFzb7SrosBvBY9-PJk-LYrhTbmENAudQyBBNJaB6Fax32DujgPp9aphv1GnuoKw/s1600/20151102graph1.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="306" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnR_59E-9XxyI4O-pUUYJWfmJ3hkbWTt7Q3K9Bzt7TPigCjhsqQQeF9MdvDoWiGFKUcDtdEhEswKpTuFzb7SrosBvBY9-PJk-LYrhTbmENAudQyBBNJaB6Fax32DujgPp9aphv1GnuoKw/s320/20151102graph1.PNG" width="320" /></a></div>
Hmm, interesting, although in this case not too surprising: as more time in the microwave passes, the sample gets hotter. But how much hotter? And how fast does it get hotter? If I want to heat a cup of water to make tea, should I put it in the microwave for 30 seconds or 5 minutes? The <i><b>rate</b></i> of heating is an interesting and important piece of information we can extract from this data!<br />
<br />
How do we calculate a rate? Rate is the change in some observable quantity divided by the change in time. If you can eat a cheeseburger in 5 minutes, your rate of eating cheeseburgers is:<br />
<div style="text-align: center;">
Change in the number of cheeseburgers / Change in time</div>
<div style="text-align: center;">
1 cheeseburger / 5 minutes = 0.2 cheeseburgers per minute</div>
In this experiment, you weren't eating cheeseburgers (well, OK, I guess you <i>might</i> have been eating cheeseburgers while you were watching water heat up…), but you were observing the change in temperature as time passed, so we should be able to calculate a rate in a similar way. Looking back at the data above, we can pick any two points and look at the change in temperature divided by the change in time. For example, from 90 seconds to 135 seconds the temperature changed from 116.04<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C to 184.70<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C, so the rate over that time period was:<br />
<div style="text-align: center;">
(184.70<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C - 116.04<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C) / (135 seconds - 90 seconds)</div>
<div style="text-align: center;">
(68.66<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C) / (45 seconds)</div>
<div style="text-align: center;">
1.5<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C per second</div>
We could pick <i>any</i> two points out of our data and calculate a rate, and they would all be pretty similar, but because there is some variability in our experiment they would not all be identical. But wait, if that's all we are going to do, then why did we make a graph? Graphs are pretty, but making a graph for the sake of making a graph doesn't seem like a great use of your time. Can we use the <i>graph</i> to determine the rate of heating? Hmm, change in temperature… the vertical axis (y-axis) is temperature, so that one should track changes in temperature… and the horizontal axis (x-axis) is time… WAIT! The data points in the graph look pretty close to linear, and the slope of a line is "rise over run"… if "rise" is the change in the y-axis variable and "run" is the change in the x-axis variable, then we should be able to get the slope from the graph, and the slope should be the rate of heating! If we draw a line that looks like it fits the data pretty well, we get:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv9DFeGZeC97LyttZP4NiUPtKlfTGcBb9YWszmsiFyt4oDuGyboum-uPXst1BjhsCQl3UqpE-Al5exo2ox7KPY1AhwgwySjCA75ic5ro4NDCt_9TVReMQ2Dlus_WHsPglPYuKnKvkQvvs/s1600/20151102graph2.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv9DFeGZeC97LyttZP4NiUPtKlfTGcBb9YWszmsiFyt4oDuGyboum-uPXst1BjhsCQl3UqpE-Al5exo2ox7KPY1AhwgwySjCA75ic5ro4NDCt_9TVReMQ2Dlus_WHsPglPYuKnKvkQvvs/s320/20151102graph2.PNG" width="320" /></a></div>
From the <b><i>line</i></b> (we're not looking at specific points now), it looks like over the time period from 0 seconds to 300 seconds the temperature rises from about 5<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px; text-align: center;">°</span>C to about 390<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px; text-align: center;">°</span>C. So the rate based on the fit line is:<br />
<div style="text-align: center;">
(390<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C) / (300 seconds)</div>
<div style="text-align: center;">
1.3<span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px;">°</span>C per second</div>
By using a fit line, we can even out some of the variability associated with any two points we might choose and we should get a more reliable answer. If we look at the rate for any two adjacent points (any 15 second period in our experiment) and calculate the rate using only those two points, we would get answers as low as <span style="text-align: center;">0.75</span><span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px; text-align: center;">°</span><span style="text-align: center;">C per second and as high as </span><span style="text-align: center;">1.9</span><span style="background-color: #f9f9f9; color: #333333; font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 14px; line-height: 20px; text-align: center;">°</span><span style="text-align: center;">C per second, so using the fit line seems like a pretty good way to get a reliable single answer for the experiment.</span><br />
<br />
Good luck on your data collection and analysis.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-35378014633923654202015-08-25T08:20:00.001-05:002015-08-25T08:20:28.568-05:00Fall 2015 - Welcome to class!Fall 2015 semester has begun! Welcome to BCBT 100 - The Science of Cooking. Together we will explore the scientific foundations that humans (and pre-humans...) have used for millenia to produce and transform food. If you have ever prepared or even just eaten food, you are a scientist!<br />
<br />
Let's have a great semester!Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com1tag:blogger.com,1999:blog-1471691084198080771.post-62833423565046667192014-03-13T07:58:00.001-05:002014-03-13T09:48:32.841-05:00Make a graphHelp me help you. There seems to be some confusion that I'd really like to be able to clear up and I'd welcome some feedback. In the at-home lab activity we recently did for class (<a href="http://www.drbodwin.com/teaching/scicook/MicrowaveHeating20140227a.docx">http://www.drbodwin.com/teaching/scicook/MicrowaveHeating20140227a.docx</a>), the first data analysis section says:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjszh5XcpJU9Ij5VzyGj482kt8gpR8pCjS2CK3OOFyBT-erQfi9As415aM1K8LIYquPUzJYXG5dTi6hfrTKCUiLI5Zmlf5GDCzFcmOpYljqsz65kkhzvSn6fuKAkk-vZZ1bqoHROSmH5ZQ/s1600/20140313aplotdirections01.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjszh5XcpJU9Ij5VzyGj482kt8gpR8pCjS2CK3OOFyBT-erQfi9As415aM1K8LIYquPUzJYXG5dTi6hfrTKCUiLI5Zmlf5GDCzFcmOpYljqsz65kkhzvSn6fuKAkk-vZZ1bqoHROSmH5ZQ/s1600/20140313aplotdirections01.JPG" height="40" width="400" /></a></div>
<div style="text-align: left;">
My intention here was that the students would take the time-dependent temperature data they collected and prepare a plot that looks something like this:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOB6WUz5sXp5WO_2Ww8_O3zmopwanhGmfVfaM1reGIEoFZ-4ZctP3tmBMiP3AiEOsQeTfVglLGS4BFv44-UAWkOCZUUCi3UpqntoOftNYTOact4jl6O1jFCNZkyjLeFXCEXfYDRWswbbA/s1600/microwaveheating20140120a.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOB6WUz5sXp5WO_2Ww8_O3zmopwanhGmfVfaM1reGIEoFZ-4ZctP3tmBMiP3AiEOsQeTfVglLGS4BFv44-UAWkOCZUUCi3UpqntoOftNYTOact4jl6O1jFCNZkyjLeFXCEXfYDRWswbbA/s1600/microwaveheating20140120a.png" height="278" width="400" /></a></div>
<div style="text-align: center;">
<span style="font-size: x-small;">{<i>NOTE: This plot contains more data that I expect in the student experiment.</i>}</span></div>
A significant number of students did not realize that they needed to include a graph as part of their data analysis and assignment. I don't understand why this was not clear. I am not being snarky or condescending or angry or mean when I say that, I honestly don't understand why that instruction in the "Data Analysis" isn't clear, so I would sincerely appreciate any help on how to write that instruction more clearly. I have a couple ideas of why this was not an effective instruction:<br />
<br />
<ol>
<li>The word "plot" doesn't mean the same thing to everyone. Is there a better word that would make this more clear? Graph? "X-Y scatter plot"? I do not require students to use a spreadsheet to generate their plots because I don't want to introduce additional barriers and hand-drawn plots/graphs are sufficient for the data presentation and analysis in this class… Would it be better to require computer generated plots/graphs just to reinforce that a graph is required for the data presentation and analysis?</li>
<li>Is this more a symptom of the broader problem of "science is hard" rather than poorly written instructions? If a student firmly believes that "science is hard" or "I'm not good at math", then the student is likely to accept a lower standard for himself or herself and perform below his or her abilities. </li>
<li>Do the students just not care? I refuse to believe that this is the most common problem; the vast majority of the students in this class are dedicated hard workers and really want to learn something. At the same time, the students taking this class are not (on average) the typical "sciencey" student, they are taking this course because they see it as one of the easier options for fulfilling the science requirement of their degree. That means that there are at least a few (and they're usually not that hard to identify) who are just in the class to do the bare minimum to pass and have no real interest in learning any more than they need to squeak by with a "C".</li>
</ol>
<br />
There is no magic single answer to this issue, BUT if there are some simple fixes (change the wording, etc) that will help some students succeed in this class, I'm happy to consider them. Anonymous comments are permitted here, so feel free to be as open as you would like. I'm always open to learning new and better ways to do things, so open feedback is helpful.<br />
<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com1tag:blogger.com,1999:blog-1471691084198080771.post-90685773222657427052014-03-09T18:55:00.000-05:002014-03-09T18:55:31.889-05:00Lab Assignment Tips<div>
After looking over your Lab 1 assignments, there are a couple general points that I think would help everyone make some improvements on future assignments:</div>
<br /><b>1. Individual vs Group Assignments</b><br /><div>
For your labs (and everything else in BCBT 100), you must turn in individual assignments to receive a grade. Even if you're working with a partner (or 2) on a lab experiment, each partner is required to turn in an individual assignment for grading. This doesn't just mean 2 copies of the same assignment with a different name at the top (that would be plagiarism and could result in your expulsion from the University), but individual assignments from each partner. I expect and encourage you to discuss your experimental observations and conclusions with others in the class, and if you are working with a partner I expect that the raw data you use will be the same, but your responses to questions should be <i>yours</i> and in <i>your voice</i>. </div>
<div>
<br /></div>
<div>
<b>2. Complete Answers</b><br />Especially in labs, always assume that there is a "Why?" or an "Explain" part of every question. Give me an answer that shows me a little bit of your thought process. "How confident are you in the accuracy of your result?" shouldn't just be answered with "Very confident" or "Yes." {I'm not sure how "Yes" even <i>could</i> be an answer to that question...} If you are "very confident" in your result, there must be some reason for your confidence. And no, the answer is not "I am very confident in my result because I am just that good." An answer that would be quite convincing and give me a good indication of your thought process would be something like "The error in our repeated measurements {+/- 0.014} is quite small compared to the average of the repeated measurements {17.372}, so we are very confident in the precision of our answer." I can say with nearly 100% certainty that I will almost never ask a question that I expect to be answered with a single word. </div>
<div>
<br /></div>
<div>
<b>3. Show Your Work</b></div>
<div>
Whenever you have to do any math, show at least 1 sample calculation for each step of the math you have to do. It's not always obvious there some of your numbers come from, so a little bit of help would be nice. {This is closely related to the "Complete Answers" tip above...}</div>
<div>
<br /></div>
<div>
<b>4. Graphs Should Fill the Available Space</b></div>
<div>
This is especially true when you're trying to fit a line to a bunch of data points by eye. If you have a half page of space for your graph, don't squeeze all the data into a little postage stamp in the corner. By spreading out the data, you will minimize the error in your line fit. Scientists devote a stunning amount of time to analyzing and trying to minimize error in their experiments; be a good scientist!</div>
<div>
<br /></div>
<div>
I'll post more tips as they come up. When in doubt, always ask.</div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-30713702510559957172014-03-05T12:09:00.000-06:002014-03-05T12:16:44.700-06:00Study Guide AnswersA few people have asked if I'm going to post "answers" to the study guide for Exam 2.<br />
<br />
Short answer = no.<br />
<br />
Less short answer = The "answers" are already posted. For Exam 1 I posted specific sample multiple choice questions, so there was an answer key. For Exam 2 (and likely Exams 3 & 4...), I posted a study guide that contains open-ended questions. The answers to these questions are contained in the slides I used in class and/or the assigned readings from the textbook. By posting questions this way, I hope to encourage you to think about many of these concepts a little more broadly rather than focus on picking the exact right answer from a list of possible choices.<br />
<br />
For those of you who may be a little anxious that the exam will be a whole different format than Exam 1, fear not; your actual exam will still be multiple choice. By preparing for the exam with open-ended questions, you will be better prepared to answer a variety of multiple choice questions on each topic rather than just answer the exact questions you have studied. Some of the study guide questions will probably show up on the exam as multiple choice questions, but by preparing for those questions without the restriction of a specific set of multiple choice options, you will be better prepared to succeed.<br />
<br />
If you <i>really</i> want to see something that looks like answers to some of the questions on the study guide, many of these can be found in one of these links:<br />
<a href="http://www.drbodwin.com/teaching/scicook/bcbt100aexam2practicek.pdf">http://www.drbodwin.com/teaching/scicook/bcbt100aexam2practicek.pdf</a><br />
<a href="http://www.drbodwin.com/teaching/scicook/bcbt100aexam3practicek.pdf">http://www.drbodwin.com/teaching/scicook/bcbt100aexam3practicek.pdf</a><br />
<br />
Good luck.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-85366260595690805352014-01-20T12:36:00.000-06:002014-01-20T12:36:04.031-06:00Topics for Spring 2014I've tallied up your responses from the first day of class and it looks like the most popular topics for the semester are (in no particular order):<br />
<br />
Chocolate<br />
Bread and baked goods<br />
Cheese<br />
Spices and flavor matching/mixing<br />
International cuisines<br />
Nutrition and food safety<br />
Characteristics of different cooking methods<br />
<br />
That sounds like a good mixture of topics! We'll also spend some time on fruits, vegetables, and dairy to round things out. We will likely have our first experiment posted in the next couple days, so be ready to observe, question, test, and repeat!Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-66808466178388474992014-01-14T08:05:00.000-06:002014-01-14T08:05:09.304-06:00Welcome to BCBT 100 (Spring 2014)Welcome to The Science of Cooking (BCBT 100) for Spring 2014. This semester we will be exploring the science of food and the changes that take place in food during cooking and other preparations. A few things to remember when looking at the science of food and cooking:<br />
1. This is a <i>science</i> class. That doesn't mean it's "hard", that just means that we'll be using a scientific approach to to topics we explore.<br />
2. Be curious. Curiosity is the key to all good science.<br />
3. Be open to new experience. You don't "like" a certain food? Why not? Understanding why you have a preference can help you enjoy a wider variety of foods and experiences.<br />
4. Have fun! This is food afterall.<br />
<br />
In addition to posting info here on the blog, I will also be tweeting using #ChemKitchen. Let's have a great semester!<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-75175730565127437312012-12-11T15:37:00.001-06:002012-12-11T15:37:04.368-06:00BCBT 100 – Exam 4 Practice Questions {Bodwin – Fall 2012}<br />
<div class="MsoNormal">
<b>BCBT 100 – Exam 4
Practice Questions {Bodwin – Fall 2012}<o:p></o:p></b></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe and
identify the components of a seed.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
difference between monocot and dicot seeds. Give examples of each.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What are some
similarities and differences between grains, legumes, and nuts? How do they
grow, what food molecules do they contain, etc</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
How is flour
made? (from the McGee book)</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What is “leavening”?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
process and chemical reaction of chemical leavening.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What is the
difference between baking soda and baking powder? Why are BOTH sometimes called
for?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What is gluten?
How is gluten formed? What type of interactions between molecules are present
in gluten? </div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
How does
kneading encourage gluten formation?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
ways in which gluten can be modified when making a dough. What physical or
chemical steps can be taken to increase gluten formation? What physical or
chemical steps can be taken to decrease gluten formation?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
In aerobic metabolism
of sugars, what are the products of the chemical reaction?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What are the
products of the chemical reaction when yeast metabolizes sugars?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
differences between yeast-leavening and chemical-leavening. What are some
advantages of each?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What is Charles’
Law?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
If the absolute
temperature of 6.0L of a gas is tripled, what is the new volume of the gas?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What role does
starch play in the structure of baking bread?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Why is it
important that the bubbles in baking bread merge and pop during the baking
process?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What are some
of the results/effects of having a lot of steam present when baking breads?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What does it
mean for a bread to become “stale”? How can staleness be prevented? Reversed?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
How does the
protein content of different types of flour affect the bread made from those
flours?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What food
molecules must be present for Maillard browning to occur?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What
property/properties do aldehydes contribute to foods?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Above what
temperature does significant Maillard browning take place?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What cooking conditions
encourage Maillard browning? What cooking conditions inhibit Maillard browning?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Above what
temperature does significant caramelization take place?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What chemical
reaction is catalyzed by phenol oxidase?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What molecular
changes take place that cause enzymatic browning?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What conditions
would encourage more sugar browning/caramelization when cooking?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What role does
water play in most browning reactions? </div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Where is
chocolate grown?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
process of making chocolate from the tree to the finished bar.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What type(s) of
browning is/are responsible for the brown color of chocolate?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Which type of
chocolate plant has the most delicate flavors?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What is the
purpose of “Dutch processing” of cocoa powder?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
Describe the
molecular changes that take place when chocolate is tempered.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
If a chocolate
bar is not stored properly it can have a “dusty” appearance. Describe what has
happened.</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What causes
chocolate to “seize”?</div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
What are the
advantages of letting chocolate melt in your mouth when tasting it?</div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-58441054060806505952012-10-24T17:01:00.000-05:002012-10-24T17:01:22.368-05:00Looks like Fruit & Veg!But don't worry, we'll also do breads in a couple weeks.<br />
<br />
On the fruit & veg side of things... We'll very likely do some tasting in the coming week or so. Are there any fruits or vegetables that you have never tried that you're curious about? Some vegetables that might be a bit less common (but I know I can get pretty easily...) might be some of the root vegetables (rutabaga, parsnip, turnip), or some different varieties of potato, or some different types of greens... On the fruit side, some of the less-typical citrus fruits, or unique berries...<br />
Basically, if there's a fruit or vegetable (broadly defined) that you've always wondered about, let me know, we might use that as part of an in-class tasting, and you can have a new and exciting experience.<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-63344179327081807612012-10-23T20:20:00.000-05:002012-10-23T20:20:03.615-05:00Next topics...Fruits and Vegetables are winning in the early returns, but the polls are still open in the rural areas. Vote early, and in this case you can even vote often.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-67567699121305323402012-10-21T21:20:00.001-05:002012-10-21T21:20:08.504-05:00Exam #2 Practice Problems<br />
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What is
cheese? – Milk that has been curdled by acid and rennet that has had most of
the water removed<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What is
the primary role of salt in cheese? – Preservative <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Some
enzymes used in cheesemaking hydrolyse fats and proteins during the aging
process. How does this affect the final cheese? – Hydrolyzed fats and proteins
usually lead to smaller molecules that contribute flavor and aroma. They can
also tweak the texture.<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Why is it
important to get chymosin (rennet) from young calves rather than adult cows? –
Cows only produce chymosin while they are feeding on milk, once they’re off the
milk, chymosin production drops off very quickly<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. How was
rennet “discovered? – It was a happy accident. When calf stomachs were used as
waterproof bags for milk storage and transportation, the rennet curdled the
milk into cheese<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
specific protein does chymosin (rennet) react with during cheesemaking? – Chymosin
reacts with the kappa-casein proteins that coat casein micelles… This lets the “gooey”
inner caseins to stick together and form a network of casein micelle chains<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. When
chymosin (rennet) reacts with protein during cheesemaking, what happens on a
molecular level? – Rennet “shaves” some of the kappa-casein off the outside of
the casein micelles and they stick together<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. When acid
reacts with protein during cheesemaking, what happens on a molecular level? –
Acid denatures the casein proteins much more completely, allowing the
individual casein protein strings to interact <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What are
the main roles of <i>propionibacteria</i> in
cheesemaking? – This is the hole-making bacteria<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. <i>Brevibacterium linens</i> mainly contributes
what to cheese? – This is the “stinky cheese” bacteria<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What are
the properties of <i>Penicillium roqueforti</i>
and other “blue molds” used in cheesemaking? – Can survive low oxygen, found
inside the cheese, digests fats, contributes sharp/peppery flavor<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. How are the
“white molds” used in cheesemaking different from the blue molds? – Surface molds,
digest proteins, make creamy texture<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. When
slowly adding heat to try and melt cheese, what component (food molecule) is
affected first? Second? – Fats melt first, proteins denature next, water starts
to boil/evaporate off, fat/protein start to brown/burn, things start on fire,
chaos ensues<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. In dishes
that contain melted cheese, what causes “stringiness”? – Too many
protein-protein interactions, lots of stirring<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Where is
most of the fat found in eggs? - Yolks<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What does
the color of the shell of a chicken egg tell you? – It can indicate the breed
of chicken, but not much more<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What does
amylase (an enzyme found in egg yolks) do? – We talked about this one in the
food molecules section, amylase digests (hydrolyzes) amylose, that’s starch<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. After
water, what is the largest component (food molecule) of egg white? – Albumen proteins<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
happens on a molecular level when eggs are cooked “hard”? – Proteins denature and
get all tangled up<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Describe
the molecular changes that take place when egg whites are whipped. – Mechanical
shearing/denaturing of proteins,
proteins stretch and tangle, capture air bubbles<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What role
does cream of tartar serve in whipped egg whites? – It’s an acid, it prevents
the formation of too many disulfide bonds<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Why are
very strong interactions, like disulfide bonds, unfavorable in whipped egg
whites? – Very strong interactions tend to squeeze water out and limit the
ability of the protein chains to slide by each other while the meringue is
forming/building<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. How does
heat affect an albumen foam (a meringue)? – Heat dehydrates the meringue, also
denatures additional proteins (ovalbumen) to form more network connections, if
there’s sugar present the heat will also dehydrate and form a bit of a
sugar-strand network<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
component of an egg preparation has a very high heat capacity? - Water<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
component of an egg preparation is an excellent heat insulator? - Air<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
component of an egg preparation can melt, solidify or separate depending on
temperature? - Fats<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What
component of an egg preparation affects the structure and texture of the final
dish depending upon whether it has been denatured or not? - Proteins<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What is “candling”
and why is it done? – Shining light through an egg to see the yolk and
determine the egg’s grade<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Describe
the different grades of eggs. – AA = thicker albumen, prominent chalazae; A =
less thick, weaker chalazae; B = industrial eggs, yolk swirls around inside the
shell<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What is
specific heat capacity? – The amount of heat/energy required to raise a given
amount of a substance by a given temperature. Usually calories per
gram-degree-Celcius<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. If the
specific heat capacity of water is 1 calorie per gram-degree-Celcius (1cal/g•°C),
adding 100.0 calories of heat to 20.0g of liquid water at 17°C should
{increase/decrease} the temperature to _______°C. – This should increase the
temperature by 5°C to 22°C. <o:p></o:p></span></div>
<div align="center" class="MsoNormal" style="margin-left: .25in; text-align: center; text-indent: -.25in;">
<span style="font-size: 10.0pt;">(100.0calories) / (1cal/g°C)
= 100 g°C<o:p></o:p></span></div>
<div align="center" class="MsoNormal" style="text-align: center;">
<span style="font-size: 10.0pt;">(100 g°C) / (20.0g) = 5°C.<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. What role
does the water bath play when cooking/baking a custard? – Even heating, slows
down and evens out the denaturing of proteins in the custard, manages heat
transfer<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<span style="font-size: 10.0pt;">#. Why is
tempering important? – Tempering evens out the denaturing of proteins. If hot
and cold were just dumped together all at once, some proteins would denature
quickly where the solution was hot and the result would be a clumpy mixture<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: .25in; text-indent: -.25in;">
<br /></div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-33127780368982617842012-10-20T09:41:00.001-05:002012-10-20T09:41:47.039-05:00Exam 2 Format<div><p>Exam 2 (and all of your exams in BCBT 100) will be a multiple choice exam. The practice questions I posted do not have "multiple choice" answers included with them because when you are studying for the exam I want you to be thinking about the substance of the questions and topics, not just picking the correct answer out of a list of 4 or 5 options. Good luck and let me know if you have other questions.</p>
<p>(I'll post answer to the practice questions some time late today or tomorrow, make sure you look at the questions and try to formulate a response BEFORE you check the answers.)</p>
</div>Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-62844534730298657142012-10-19T09:47:00.001-05:002012-10-19T09:47:36.922-05:00You're the expert!One of the nice things about a science class based on food and cooking is that in some cases YOU have real first-hand experience with the topics we're discussing. That means that sometimes (maybe even quite often), you will have experience or insight that is beyond what I have. I like that! It means that I can learn something too, and I always try to learn at least 1 new thing every day.<br />
Related to this, someone pointed out a pronunciation I slipped up on in class yesterday... I have a very basic understanding of German, and in reading what was written on my slide while I was talking and thinking about what was coming up, I did a really bad job on the word "kuchen". It is absolutely NOT pronounced "koo-chin"... The typical American English "ch" pronunciation is generated almost entirely in the front of the mouth with the tongue and the teeth (it's a more "dental" sound), whereas the "ch" in "kuchen" is generated in the back of the mouth and throat, almost as if you're pronouncing a "hard c" and an "h" at the same time, a little like the "ch" in "chalazae" or "Bach". When this German "ch" is in the middle of a word, it is often pronounced almost like a "g", but a little farther back in the mouth/throat.<br />
The biomechanics of linguistics is really pretty fascinating, and if you think about just how the sound of different letters and words are produced in the mouth, it's fun to experiment. Most people don't think about the way tongue, teeth, lips, cheeks, throat and lungs interact to do something as "simple" as speaking, if this is something you're really interested in you should check out the Speech, Language, Hearing Sciences department at MSUM.<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-70101643825861529872012-10-19T09:25:00.000-05:002012-10-19T09:25:03.389-05:00Practice questionsExam #2 is coming up on Tuesday... I've posted some practice questions {<a href="http://www.drbodwin.com/teaching/scicook/bcbt100aexam2practice.pdf">http://www.drbodwin.com/teaching/scicook/bcbt100aexam2practice.pdf</a>}, take a look at them. I posted them in a little more open-ended format to encourage you to think about the question a little more rather than just ferret out which answer is correct. I'll post answers some time over the weekend, make sure you look at <b><u><i>and think about</i></u></b> the questions before you look at the answers. Good luck.<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-62926040487557273802012-10-13T09:37:00.000-05:002012-10-13T09:37:35.537-05:00Spatulas<br />
<div style="margin-bottom: 0in;">
The word “perfect” has a lot to
live up to, and although the truly “perfect” spatula may not
exist, I think there are a few that come close. The criteria I use to
evaluate spatulas are pretty simple.</div>
<div style="margin-bottom: 0in;">
1. Material – At this point in time,
I really don't see any good reason to buy a spatula that is not
heat-resistant. A good silicone spatula is flexible, durable, stable,
stain resistant, and should be heat resistant to 600<span style="font-family: Times New Roman, serif;">º</span>F
or more. Although a good new rubber spatula might have a few
advantages, rubber spatulas are not heat resistant, prone to stains,
and can get a bit “gummy” over time. If I had an active enough
kitchen that I could take advantage of a wide variety of spatulas, I
might be willing to stock a few silicone spatulas and a few rubber
spatulas, each for their own unique purpose, but personally, I would
greatly prefer to have consistent spatulas that are all good (or at
least good enough) for any application</div>
<div style="margin-bottom: 0in;">
2. Construction – Spatulas (and many
other kitchen tools) have the potential to be fertile grounds for
contamination and bacteria or mold growth. The best way to prevent
this is to clean utensils well, and this is infinitely easier if
there are fewer gaps and seams and joints. That means any spatula
that is a single piece will be much easier to clean and keep clean.
One-piece construction also means that the head of the spatula will
never fall off or slip from the handle. There are very few rubber
spatulas that offer 1-piece construction, so once again, silicone
offers a distinct advantage. Having 1-piece, all-silicone
construction also means that when using the spatula for “hot”
applications, you never have to worry about melting or scorching the
handle of a silicone-headed 2-piece spatula.</div>
<div style="margin-bottom: 0in;">
3. Price – This is, honestly, a minor
consideration. A good quality $10 spatula will usually be much more
durable than a $2 spatula, but the difference in price between a
“good” spatula and a “cheap” spatula isn't really that
significant. With some kitchen tool, the price range is pretty broad.
For example, frying pans can range from $10 to $200+, but even a very
high quality spatula with a prestigious brand name probably won't
cost more than $25-30, and a good quality tool can be found quite
easily for $10-15.</div>
<div style="margin-bottom: 0in;">
My favorite spatula is a Chef'n brand
1-piece silicone model similar to this one
{<a href="http://www.target.com/p/vibe-switchit-spatula/-/A-13385306#prodSlot=medium_1_1">http://www.target.com/p/vibe-switchit-spatula/-/A-13385306#prodSlot=medium_1_1</a>
}, although my specific spatula is not colored.
</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyci4My1g4V-t21Q39I1IN8DDFG-cPKxWx2lgNrvAIrqKHjNN-SuOidKr6yL-LhXUrFnPVLWIlhfxlHDgXffYTAjeeL0TZzo4wvSyzR6gNsiq2IVIjvxrip3JW66Wu704w0DvGX2o0sbw/s1600/spatula01.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyci4My1g4V-t21Q39I1IN8DDFG-cPKxWx2lgNrvAIrqKHjNN-SuOidKr6yL-LhXUrFnPVLWIlhfxlHDgXffYTAjeeL0TZzo4wvSyzR6gNsiq2IVIjvxrip3JW66Wu704w0DvGX2o0sbw/s320/spatula01.jpg" width="320" /></a></div>
<div style="margin-bottom: 0in;">
This has been a wonderful tool in my
kitchen for quite a few years, but has picked up a couple small nicks
and dings, so I'm probably in need of a new one. I'll probably wander
through local stores for a new spatula, but I'd be pretty happy if I
could either find the exact same model or perhaps something like this
one {<a href="http://www.chefn.com/Product.aspx?id=143">http://www.chefn.com/Product.aspx?id=143</a>
}</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBqxidzP_WRfxA2o8Hi22MK5-pXMgbl_anSMw_X25UzB8ncegaZfJ0zPNIeJsvW6mBGCe5WJxnv0wyVkNg9LwIS3h22IpfmAuA3Nk08dKjYY7fp07Tw8vfZs8sGTb9RwohCdJkqqerVRk/s1600/spatula02.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBqxidzP_WRfxA2o8Hi22MK5-pXMgbl_anSMw_X25UzB8ncegaZfJ0zPNIeJsvW6mBGCe5WJxnv0wyVkNg9LwIS3h22IpfmAuA3Nk08dKjYY7fp07Tw8vfZs8sGTb9RwohCdJkqqerVRk/s320/spatula02.PNG" width="71" /></a></div>
<div style="margin-bottom: 0in;">
<br /></div>
<div style="margin-bottom: 0in;">
I would be perfectly content to use a
brand other than Chef'n, but my current Chef'n spatula has been a
wonderful tool so I'd be happy to display some brand loyalty.
</div>
<div style="margin-bottom: 0in;">
Do I really put this much thought into
something as pedestrian and work-a-day as a spatula? Well, yes, but
it's almost by accident. As with many kitchen tools and other things,
you don't really think about preferences or quality until you
accidentally buy something that has some very obvious advantages.
That was the case with this spatula.
</div>
<div style="margin-bottom: 0in;">
<br />
</div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com1tag:blogger.com,1999:blog-1471691084198080771.post-34696932590856230842012-10-09T09:32:00.003-05:002012-10-09T09:32:59.713-05:00Food as ScienceOne of the greatest things about food is that there is a LOT of fascinating science going on that can be explored by anyone. The conditions are (usually) safe, the ingredients can be pretty inexpensive (although some can be very expensive), and the result can (usually) be eaten. Take advantage of these things when it's time for a meal. Thinking about the science behind simple processes like whipping and baking and frying can dramatically improve the quality of the food you prepare.<br />
<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-31405489128365943622012-09-26T16:18:00.000-05:002012-09-26T16:18:00.290-05:00Course grades...A few people have asked "What was my grade on Exam 1?". I know I mentioned some estimated letter grade ranges in class, but you really have to be a little careful about thinking in letters. Think about your grade in numbers and the total points you have accumulated. I do not determine your final course grade by looking at the letters you may have earned on exams, I look at the numbers. Why is this an important distinction? Here are a couple examples. Let's say you are taking a class where your grade is determined by your score on 4 exams, and to make the math a little easier, let's say that each exam is worth 100 points and the class is using a typical 90/80/70 percent scale for A/B/C and there are no "+/-" grades.<br />
<i><br /></i>
<i>Example 1</i>: Your exam scores are 90, 91, 82, 92. If we assign letters to those individual exams, you got A, A, B, A. Three "A" grades sounds pretty good! What grade would you get for this course? You've earned 355 points out of 400 possible points, that's just under 89%. Look's like a B.<br />
<i><br /></i>
<i>Example 2</i>: Your exam scores are 78, 87, 79, 78. If we assign letters to those individual exams, you got C, B, C, C. Hmm, looks like a "C" is in your future. But wait! You've earned 322 points out of a possible 400 points, that's 80.5%. The result is a "B" and everyone cheers with delight!<br />
<br />
This is why I'm always a little hesitant to assign grades to individual exams or assignments, it can lead to incorrect expectations.<br />
<br />Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-79430951481137110752012-09-18T13:08:00.003-05:002012-09-18T13:08:59.024-05:00Key and corrections posted...I posted the answer key for those sample questions on my website (<a href="http://www.drbodwin.com/teaching/bcbt100.php">http://www.drbodwin.com/teaching/bcbt100.php</a>). I also posted an updated version of the sample questions, I spotted a couple typos that have been corrected.<br />
<br />
I have one other clarification from class today... Any <i>topic</i> that has been mentioned in class can appear on the exam. There are <i>details</i> within a topic that might have been part of your reading assignments that were not explicitly mentioned in class, but those may still appear on the exam. You are responsible for the reading assignments. The reason this came up in class is that someone specifically asked about ice cream... we didn't get into ice cream in class, but it was part of your reading assignment... that's a <i>topic</i> that we didn't mention in class, so I'm not including ice cream on the exam. Hmm, that may have been more confusing than the original confusion... OK, to be (hopefully) clear, ice cream specifically will not be on this exam. All the other parts of your reading and the things we did in class might be on the exam.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-31931200924221306102012-09-14T21:30:00.000-05:002012-09-14T21:30:08.936-05:00Review/Practice questions postedI've posted some review/practice questions for our upcoming exam. Good luck and let me know if you have questions. <a href="http://www.drbodwin.com/teaching/scicook/bcbt100aexam1practice.pdf">http://www.drbodwin.com/teaching/scicook/bcbt100aexam1practice.pdf</a>Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-40345369397024366242012-09-13T21:12:00.000-05:002012-09-13T21:12:06.924-05:00Intermolecular Forces and Dissolving<br />
<div style="margin-bottom: 0in;">
Question from
email------------------------------</div>
<div style="margin-bottom: 0in;">
I have a question in relation with our
today's lecture, yogurt comes out from milk then why yogurt can not
dissolve in water like milk, that completely mixes with water.
</div>
<div style="margin-bottom: 0in;">
-------------------------------------------------------</div>
<div style="margin-bottom: 0in;">
The short answer is that yogurt
contains networks of proteins that are solid enough to make yogurt
thick, but not so solid that yogurt is just a big solid lump. To
explain better, we need to think about why things dissolve. Let's
start with a lump of sucrose (table sugar) and a glass of water. The
sucrose is solid because the intermolecular forces between the sugar
molecules are very strong. The water is liquid because the
intermolecular forces are also quite strong, but the individual water
molecules can slide past each other. When the lump of solid sugar is
dropped into the glass of liquid water, the sugar dissolves.
Energetically, we can think of this as a series of interactions being
broken and formed, with the result being whatever state bring us to
the lowest energy. If the sugar is going to dissolve in the water, we
need to break sugar-sugar interaction (requires energy) and we need
to break water-water interactions (requires energy). At the same
time, we need to form water-sugar interactions, which liberates
energy. If the energy we get back from forming water-sugar
interactions is greater than the energy required to break the
sugar-sugar and water-water interactions, then the sugar will
dissolve in the water. This is the part of chemistry called
thermodynamics, which looks at how changes in energy affect chemical
reactions. Looking at the following figure:</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicWpsURG3UynS2uk-1lMcLWAPOfvI1-1fkVDJR7qfzu3pbvqiFNHva7UoWSS55xSA-ox21biophqX38NbDdcDx7Y0Kw5AdMvtC7I6dRa7HaU29zI-CneH4rml2QE2qdBWF-vyiagUvWRc/s1600/thermoredox.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="285" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicWpsURG3UynS2uk-1lMcLWAPOfvI1-1fkVDJR7qfzu3pbvqiFNHva7UoWSS55xSA-ox21biophqX38NbDdcDx7Y0Kw5AdMvtC7I6dRa7HaU29zI-CneH4rml2QE2qdBWF-vyiagUvWRc/s320/thermoredox.png" width="320" /></a></div>
<div style="margin-bottom: 0in;">
<br />
</div>
<div style="margin-bottom: 0in;">
Going from “A” to “B”
represents breaking sugar-sugar and water-water interactions, both of
which require energy to be added to the system, noted by the skinny
red arrow. When water-sugar interactions are formed, energy is taken
out of the system, represented by the skinny green arrows. If the
amount of energy we get back from forming water-sugar interactions is
relatively small (going from “B” to “C” in the figure), then
the net change in energy for the whole process is positive, and the
sugar will not dissolve. This overall change is represented by the
fat red arrow. If, on the other hand, the amount of energy we get
back from forming water-sugar interactions is relatively large (going
from “B” to “D” in the figure), then the net change in energy
for the whole process is negative (fat green arrow), and the sugar
probably will dissolve.</div>
<div style="margin-bottom: 0in;">
Now back to the yogurt question. The
intermolecular interactions we have to think about in yogurt are
protein-protein, water-water, and protein-water. {Proteins make this
a little trickier because proteins have portions that are more
hydrophilic and portions that are more hydrophobic.} The
protein-protein interactions in yogurt are pretty strong, so the
proteins stick together to form nets, BUT there are also parts of the
protein molecules that have fairly strong protein-water interactions.
The proteins do not form a hard, compact, crystalline solid like a
sucrose crystal because they can form a lot of protein-water
interactions, but the parts of the protein molecules where the
protein-protein interactions are strong prevent the whole molecule
from dissolving in water.</div>
<div style="margin-bottom: 0in;">
The even deeper part of this question
actually shows up in the words that were used. yogurt does not
“dissolve” in water, but milk “completely mixes” with water.
Remember, milk is an emulsion, so although it does mix with water,
it's not really “dissolving”. In that sense, milk and yogurt are
similar, the difference being that the parts of milk that do not
dissolve are tiny little droplets and clusters that can freely float
around in the aqueous part of the milk, while the part of yogurt that
doesn't dissolve is a large, extended network of proteins that makes
yogurt thick and clumpy. And delicious.</div>
<div style="margin-bottom: 0in;">
<br />
</div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com5tag:blogger.com,1999:blog-1471691084198080771.post-26437355474069558522012-09-06T16:25:00.002-05:002012-09-06T16:25:28.848-05:00Carbs!!<br />
<div style="margin-bottom: 0in;">
Carbohydrates. Some people think
they're the enemy, but they're really just an innocent little (or not
so little) food molecule. Carbohydrates are a class of food molecules
that consist of carbon (“carbo”) and hydrogen & oxygen
(“hydrate”).</div>
<div style="margin-bottom: 0in;">
<b><i>Monosaccharides</i></b></div>
<div style="margin-bottom: 0in;">
These are simple sugar molecules with a
single ring. There are quite a few possibilities, but the 3 main
monosaccharides in food are glucose, galactose and fructose.</div>
<div style="margin-bottom: 0in;">
<b><i>Disaccharides</i></b></div>
<div style="margin-bottom: 0in;">
If two monosaccharides react to
liberate a water molecule (a <i><u>dehydration</u></i> or
<i><u>condensation</u></i> reaction), they form a disaccharide. There
are many possible combinations of monosaccharides, but again, when
we're looking at food and cooking, there are 3 main disaccharides:
sucrose (table sugar, made from glucose-fructose), maltose (grain
sugar, made from glucose-glucose) and lactose (milk sugar, made from
glucose-galactose). To get the energy out of a disaccharide, it's
usually necessary to break the two halves apart again by <i>adding</i>
a water molecule (a <i><u>hydrolysis</u></i>
reaction, the reverse of a dehydration reaction). This can be
accomplished a couple different ways, one of which is by enzymes. The
enzymes that break up disaccharides are named to reflect the
disaccharide they hydrolyze: sucrase hydrolyzes sucrose, maltase
hydrolyzes maltose, and guess what lactase hydrolyzes?
</div>
<div style="margin-bottom: 0in;">
<b><i>Starches</i></b></div>
<div style="margin-bottom: 0in;">
If
many glucose molecules react to form a glucose polymer, one possible
polymer is <i><u>starch</u></i>.
There are 2 kinds of starch; amlyose is a single chain of glucose
molecules that usually forms a helical structure, and amylopectin is
a branched chain of glucose molecules. Both are present in plants,
the relative amounts of amylose and amylopectin vary, although
there's almost always more amylopectin than amylose. Amylose can by
hydrolyzed by an enzyme called... amylase. Is there a pattern? I
think so...</div>
<div style="margin-bottom: 0in;">
<b><i>Glycogen</i></b></div>
<div style="margin-bottom: 0in;">
Plants
make glucose polymers to store energy rather efficiently and
compactly, so it would make sense that animals would also use a
glucose polymer to store energy. The animal glucose polymer is called
glycogen and is even more branched than amylopectin.
</div>
<div style="margin-bottom: 0in;">
<b><i>Cellulose</i></b></div>
<div style="margin-bottom: 0in;">
With a
very small change in structure, alpha-glucose becomes beta-glucose.
There's a very nice side-by-side animation of these two molecules at
{<span style="color: blue;"><span style="font-size: x-small;">http://www.biotopics.co.uk/JmolApplet/alphabetajglucose2.html</span></span>}.
Polymers of beta-glucose are called cellulose, and this tiny
structural change means that it is MUCH more difficult to hydrolyze
cellulose that polymers made of alpha-glucose. Cellulose is what is
typically called “dietary fiber” and passed through the digestive
tract relatively intact.</div>
<div style="margin-bottom: 0in;">
There
are a LOT of fascinating details in the structure, function and
reactivity of carbohydrates, this is just a little taste.</div>
Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-16780370190562059512012-09-01T19:56:00.002-05:002012-09-01T19:56:43.453-05:00Atomic Structure - Nuclear ChemistryFrom email:<br />
<blockquote>
I was reading a book of "on Food and Cooking" and i came up with the
question that, why proton in an atom does not repeal each other or why
electrons of same atom does not attract it's own proton? i have read
it's answer also but i am still unclear. could
you please explain this</blockquote>
Atoms are pretty amazing things for the exact reasons you point out. Protons are positively charged, so if like charges repel each other, the protons in an atom should be trying to get as far apart as possible. But all of the positively charged protons in an atom are crammed into the tiny space of the nucleus.This was pretty confusing to the scientists who originally discovered the structure of the atom, but their data was conclusive, so additional research was required to explain their observations.<br />
There are four basic forces in the universe: gravitational forces, electromagnetic forces, the weak nuclear force, and the strong nuclear force. The strong nuclear force is <i>extremely</i> strong, but it only acts over a very small distance, probably about the size of a proton or neutron. When 2 protons are brought very close together, the strong nuclear force is able to act and stick the protons together to form a nucleus.<br />
The electrostatic/electromagnetic forces that cause protons to repel each other ("like charges repel") can act over a much longer distance than the strong nuclear force. This is why atoms don't just melt into each other under normal conditions; when two nuclei approach one another, the repulsive force between these positive charges pushes the nuclei apart. If the two nuclei are smashed together hard enough, the protons can get close enough to allow the strong nuclear force to take over and the nuclei fuse together. This is what happens in the sun. The extremely high temperatures make nuclei move very fast and the high pressure leads to a lot of collisions, so nuclei smash together and undergo <u><i>nuclear fusion</i></u>. The reverse of this process, <u><i>nuclear fission</i></u>, is what provides the energy in nuclear power plants.<br />
What about the electrons? Electrons have very little mass and are moving <i>very</i> fast. The negatively charged electrons <i>are</i> attracted to the positive charged protons in the nucleus, but are moving fast enough to prevent them from crashing into the nucleus. Because electrons are so small and moving so fast, their motion is a little more complicated (due to quantum effects, but that's a little beyond this course...), but in a very basic way it can almost be thought of as the way planets move around the sun. The planets are attracted to the sun by gravity, but the motion of the planets keeps them from crashing into the sun.<br />
In almost all chemistry and physics, properties and behavior are determined by the balancing of force. The fascinating part of science is figuring out how those different forces interact with each other.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0tag:blogger.com,1999:blog-1471691084198080771.post-75886472269062966262012-08-30T15:12:00.003-05:002012-08-30T15:12:54.496-05:00The Molecules of Food!Today in class we started looking at the molecules (and ions) that make up food. We're going to spend a few days looking at these so we can relate the behavior of macroscopic foods to the microscopic molecular changes that take place during food preparation. We'll look at 4 main groups:<br />
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<b>Water</b> - Most food is mostly water. Most of <b><i>life</i></b> (as we know it) is mostly water. Water is a tiny molecule that is bent, so one end has a more negative local charge and the other end has a more positive local charge. {That last part's not a bad definition of "polar".} This makes water molecules stick together. (Opposites attract...) Water dissolves things that are charged or polar.<br />
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<b>Inorganic components</b> - salts, minerals, and a few other assorted bits.<br />
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<b>Small organics</b> - In this case, "organic" means "containing carbon-hydrogen bonds". The term has taken on a variety of other meanings in food, but we'll stick with the "C-H bonds" definition. These can include things like vitamins, metabolic products, and other bits & pieces.<br />
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<b>BIG organics</b> - Lipids, proteins, carbohydrates, DNA/RNA - These are all much bigger molecules.<br />
<i>Lipids</i> - These are fats, mostly composed of triglycerides. The length and "saturation" of the long fatty acid chains in triglycerides define their properties. The longer and more saturated the chains are, the more effectively they can pack, meaning that they are often solids at room temperature. Unsaturation (double bonds) can put some "kinks" in these long chains that can significantly affect their properties.<br />
<i>Proteins</i> - Proteins are polymers composed of amino acid monomers. The central carbon in an amino acid has an amine group (-NH<sub>2</sub>), a carboxylic acid group (-COOH), a hydrogen (-H), and a 4th group that varies (the "sidechain"). The hydrophobicity of the sidechain determines the structure of a protein, and the structure of a protein determines the function of the protein. Proteins are the workhorses of biochemistry/biology.<br />
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We'll get to the others next week. Don't forget the quiz in D2L and enjoy your weekend.Dr. Bodwinhttp://www.blogger.com/profile/16096365638270446573noreply@blogger.com0