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Busting myths: No Virginia, some sugars aren’t better than others
Myth “Some sugars are better for our bodies than others.”
Myth “Natural, raw or unrefined sugars are better.”
Myth “It is better to use honey, maple syrup, agave syrup, or coconut sugar.”
Myth “Corn syrup is worse for us than other sugars”
Myth “Natural sugar is better than processed sugar.”
Reality: None of those claims are really true. In reality our metabolism breaks down all sugars the same way.
Agave syrup, maple syrup, coconut sugar – none of these are sugar alternatives – they are just sources of sugar.
Sucrose, a common sugar, is a disaccharide. That means it is a two-part molecule, made of glucose and fructose.
And get this – sucrose is not absorbed by the human GI tract. Instead, our intestines secrete an enzyme, sucrase-isomaltase.
This breaks down any sucrose into glucose and fructose, and it is those smaller sugars which are absorbed. So our body doesn’t care which kind of sugar we eat; the result is the same.
Image from sucraid.com/about-csid
Myth “Natural sugar is better than processed sugar.”
All sugars are processed. The so-called “processed” white sugar that people are afraid of is just sugar from a natural source, sugar cane or beets. Brown sugar? The same as white sugar, except that the molasses hasn’t been removed. Not healthier whatsoever.
“Raw honey” may be unprocessed, but it isn’t any healthier. It is just sugar mixed with water, pollen and a few other organic molecules. You’re not going to be helped by the microscopic amount of nutrients in raw honey unless you ate pounds of it a day.
Myth “High fructose corn syrup is worse for you than other sugar.”
Reality? Nope. It’s literally the same thing.
image from Examine.com, difference between HFCS and sugar
More details on this bit here – What is the difference between high fructose corn syrup (HFCS) and sugar?
Myth “Sugars higher on the glycemic index are worse for you.”
Nope. Such claims come from flawed studies, see below for details.
So, are we saying that sugar is good for you? No, we aren’t saying that either. Mainstream science already knows the answer, and people just refuse to hear it: For most people, having some sugar in our diet has always been fine. The problem comes from diets which have huge amounts of sugar, and not enough of other foods that actually are good for us.
While no one, single diet is best for everyone, science points to the same direction: Eat a balanced diet with whole grains, beans, legumes, vegetables and fruit. Have less meat, and certainly less processed meat. Eat far less fried foods. Watch your total calorie intake. Keep daily sugar and fat intake lower. There you go.
What’s wrong with those glucose versus sucrose studies?
In those studies, researchers did the following: They fed huge amounts of only one type of sugar molecule to one group of rats, and huge amounts of a different type of sugar molecule to another group of rats. Then they looked at how the health of the rats were affected over time.
Problem 1: These studies don’t resemble real world eating. Humans don’t spend entire days eating nothing but fructose or nothing but sucrose. The way that our metabolism would handle that is different from how it would handle normal eating, in which sugar is only a small part of the diet. In real life, even in poor diets, sugar is still only a fraction of the total: there are also proteins, complex carbohydrates, fats, oils, vitamins, minerals, etc.
Problem 2: Some studies attempted to see how consuming different sugars affects one’s resulting blood sugar level. Sugar molecules which create a higher result are said to be higher on a glycemic index; sugar molecules which create a lower result are said to be lower on the glycemic index. Yet these are unnatural diets in which rats ate only pure sugars. When we study the results of normal diets, with actual food, there’s almost no difference between sugars. A meal’s impact on resulting blood sugar levels depends on the amount of sugar and how fast it gets absorbed, not on the type of sugar molecule.
Problem 3: Rats do not metabolize sugars in the same ways that humans do. Hence, any inaccuracies due to the above problems become magnified, making the results non applicable to humans.
Result: The data from those studies are essentially useless.
Honors biology details
Glucose enters the glycolysis metabolic pathway at the top.
Here it is phosphorylated by Hexokinase.
Fructose enters glycolysis pathway two steps later, where it meets phosphofructokinase.
Thus, eating pure fructose allows the energy to be metabolized a bit faster than eating pure glucose.
But people don’t consume huge chunks of pure sugars. When eating anything resembling real life meals, the difference is very little.
Studies on High-fructose corn syrup (HFCS)
High-fructose corn syrup (HFCS) is also known as glucose-fructose, isoglucose and glucose-fructose syrup. There is no scientific evidence that HFCS itself causes obesity or metabolic syndrome, but rather overconsumption and excessive caloric intake of any sweetened food or beverage may contribute to these diseases.
Epidemiological research has shown that the increase in metabolic disorders, such as obesity and non-alcoholic fatty liver disease, is linked to increased consumption of sugars and calories in general.
A 2012 review found that fructose did not appear to cause weight gain when it replaced other carbohydrates in diets with similar calories.
A 2014 systematic review found little evidence for an association between HFCS consumption and liver diseases, enzyme levels or fat content.
The American Heart Association recommended that people limit added sugar (such as maltose, sucrose, high fructose corn syrup, molasses or cane sugar) in their diets.
High fructose corn syrup article
Is Sugar Really Toxic? Sifting through the Evidence
Scientific American Staff and Ferris Jabr, Scientific American, July 15, 2013
https://blogs.scientificamerican.com/brainwaves/is-sugar-really-toxic-sifting-through-the-evidence/
By consuming so much sugar we are not just demonstrating weak willpower and indulging our sweet tooth – we are in fact poisoning ourselves according to a group of doctors, nutritionists and biologists, one of the most prominent members of which is Robert Lustig of the University of California, San Francisco…
A few journalists, such as Gary Taubes and Mark Bittman, have reached similar conclusions. Sugar, they argue, poses far greater dangers than cavities and love handles; it is a toxin that harms our organs and disrupts the body’s usual hormonal cycles.
Excessive consumption of sugar, they say, is one of the primary causes of the obesity epidemic and metabolic disorders like diabetes, as well as a culprit of cardiovascular disease. More than one-third of American adults and approximately 12.5 million children and adolescents in the U.S. are obese. In 1980, 5.6 million Americans were diagnosed with diabetes; in 2011 more than 20 million Americans had the illness.
…. Because fructose metabolism seems to kick off a chain reaction of potentially harmful chemical changes inside the body, Lustig, Taubes and others have singled out fructose as the rotten apple of the sugar family. When they talk about sugar as a toxin, they mean fructose specifically.
In the last few years, however, prominent biochemists and nutrition experts have challenged the idea that fructose is a threat to our health and have argued that replacing fructose with glucose or other sugars would solve nothing.
First, as fructose expert John White points out, fructose consumption has been declining for more than a decade, but rates of obesity continued to rise during the same period. Of course, coinciding trends alone do not definitively demonstrate anything.
A more compelling criticism is that concern about fructose is based primarily on studies in which rodents and people consumed huge amounts of the molecule – up to 300 grams of fructose each day, which is nearly equivalent to the total sugar in eight cans of Coke – or a diet in which the vast majority of sugars were pure fructose. The reality is that most people consume far less fructose than used in such studies and rarely eat fructose without glucose.
…. Not only do many worrying fructose studies use unrealistic doses of the sugar unaccompanied by glucose, it also turns out that the rodents researchers have studied metabolize fructose in a very different way than people do—far more different than originally anticipated.
… Even if Lustig is wrong to call fructose poisonous and saddle it with all the blame for obesity and diabetes, his most fundamental directive is sound: eat less sugar. Why? Because super sugary, energy-dense foods with little nutritional value are one of the main ways we consume more calories than we need, albeit not the only way.
Glycemic index and obesity
Janette C Brand-Miller, Susanna HA Holt, Dorota B Pawlak, Joanna McMillan
Glycemic index and obesity, The American Journal of Clinical Nutrition
Volume 76, Issue 1, July 2002, Pages 281S–285S
https://doi.org/10.1093/ajcn/76.1.281S
Although weight loss can be achieved by any means of energy restriction, current dietary guidelines have not prevented weight regain or population-level increases in obesity and overweight. Many high-carbohydrate, low-fat diets may be counterproductive to weight control because they markedly increase postprandial hyperglycemia and hyperinsulinemia.
Many high-carbohydrate foods common to Western diets produce a high glycemic response [high-glycemic-index (GI) foods], promoting postprandial carbohydrate oxidation at the expense of fat oxidation, thus altering fuel partitioning in a way that may be conducive to body fat gain.
In contrast, diets based on low-fat foods that produce a low glycemic response (low-GI foods) may enhance weight control because they promote satiety, minimize postprandial insulin secretion, and maintain insulin sensitivity.
This hypothesis is supported by several intervention studies in humans in which energy-restricted diets based on low-GI foods produced greater weight loss than did equivalent diets based on high-GI foods.
Long-term studies in animal models have also shown that diets based on high-GI starches promote weight gain, visceral adiposity, and higher concentrations of lipogenic enzymes than do isoenergetic, macronutrient controlled, low-GI-starch diets.
In a study of healthy pregnant women, a high-GI diet was associated with greater weight at term than was a nutrient-balanced, low-GI diet.
In a study of diet and complications of type 1 diabetes, the GI of the overall diet was an independent predictor of waist circumference in men.
These findings provide the scientific rationale to justify randomized, controlled, multicenter intervention studies comparing the effects of conventional and low-GI diets on weight control.
Straight talk about high-fructose corn syrup: what it is and what it ain’t,
Straight talk about high-fructose corn syrup: what it is and what it ain’t,
John S. White, The American Journal of Clinical Nutrition
Volume 88, Issue 6, December 2008, Pages 1716S–1721S, https://doi.org/10.3945/ajcn.2008.25825B
High-fructose corn syrup (HFCS) is a fructose-glucose liquid sweetener alternative to sucrose (common table sugar) first introduced to the food and beverage industry in the 1970s. It is not meaningfully different in composition or metabolism from other fructose-glucose sweeteners like sucrose, honey, and fruit juice concentrates.
HFCS was widely embraced by food formulators, and its use grew between the mid-1970s and mid-1990s, principally as a replacement for sucrose. This was primarily because of its sweetness comparable with that of sucrose, improved stability and functionality, and ease of use.
Although HFCS use today is nearly equivalent to sucrose use in the United States, we live in a decidedly sucrose-sweetened world: >90% of the nutritive sweetener used worldwide is sucrose. Here I review the history, composition, availability, and characteristics of HFCS in a factual manner to clarify common misunderstandings that have been a source of confusion to health professionals and the general public alike.
In particular, I evaluate the strength of the popular hypothesis that HFCS is uniquely responsible for obesity. Although examples of pure fructose causing metabolic upset at high concentrations abound, especially when fed as the sole carbohydrate source, there is no evidence that the common fructose-glucose sweeteners do the same.
Thus, studies using extreme carbohydrate diets may be useful for probing biochemical pathways, but they have no relevance to the human diet or to current consumption. I conclude that the HFCS-obesity hypothesis is supported neither in the United States nor worldwide.
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How do we know how atoms are arranged in a crystal?
How do we know how atoms are arranged in a protein, an enzyme, or a fat molecule?
Each individual atom is only a few nanometers (1 x 10-10 m) wide, way too small to photograph directly.
Yet we often see images of how atoms how are arranged, like this.
Just look it this image: We see individual atoms (yellow, red, blue) connected in a precise pattern. How in the world did we see this?
Well, there’s no way to see this, in one step. Too difficult.
But there is a way to accurately visualize this, if we go through a very careful process.
The process is called X-ray crystallography.
We start with a tiny sample of whatever it is we’d like to learn about. For example, a protein or an enzyme.
First, a biochemist needs to purify cells, and extract just the one molecule that we’re interested in.
That, in of itself, is a procedure that needs to be done carefully.
Once we have a pure form of that molecule, we then crystallize it.
Of course, in order for the rest of this lesson to make sense, we need to know what a “crystal” really is. So if you haven’t already learned about this, first check out our lesson on What is a crystal?
Short version: A crystal is solid material, in which the atoms, molecules, or ions are arranged in an orderly repeating pattern.
For instance, on the left is the atom-by-atom structure of a halite crystal.
(Purple is sodium ion, green is chlorine ion.)
This crystal is so tiny, that it would take 10,000 of them to make one tiny grain of salt!
On the right is a visible salt crystal. This contains millions of such crystal units.
Well, if we have a pure chemical from a cell (protein, enzyme, fatty acid, etc.) we can slowly cool and dry this chemical until it crystallizes!
Each different kind of molecule would create a differently shaped and colored crystal.
Please understand that these crystals look tiny – maybe just 1/10 of an inch across.
Yet each crystal contains millions of repeating atomic units.
Figure 22.3. Examples of protein crystals. From left to right: β-secretase inhibitor complex; human farnesyl pyrophosphatase in complex with zoledronic acid; abl kinase domain in complex with imatinib; cdk2 inhibitor complex.
Source – Jean-Michel Rondeau, Herman Schreuder, in The Practice of Medicinal Chemistry (Fourth Edition), 2015
This crystal is then placed in front of an X-ray source.
The X-rays scatter off the atoms in a crystal.
Those X-rays fly onto either a piece of film, or a digital X-ray detector plate.
Either way, we end up with a beautiful array of dots called a diffraction pattern.
This pattern is beautiful – but doesn’t seem to look like anything?
Ah, but there’s a relationship between the placement of the atoms, and where the X-rays deflect off of them – just like there’s a relationship between a pool ball bouncing off of other pool balls.
Think about it: If you know how a pool table is set up, what balls are made of, and see how the balls move after being it, then you could use math to work backwards.
Just by seeing the results of where the balls are scattering to, you could work backwards to figure out where the balls originally where.
from Banks and Kicks in Pool and Billiards, Dr. Dave Alciatore, Billiards and Pool Principles, Techniques, Resources
The same is true here: We can use math to figure out where each individual atom in the molecule is!
Let’s follow the steps below:
On the left, we see X-rays leave a source. Some of these x-rays hit a lead screen. All those X-rays are stopped.
Only a thin, focused beam of X-rays makes it thru the slit.
Those X-rays hit our crystal sample.
The X-rays bounce off the atoms, like pool balls bouncing off of each other.
(This GIF created by Abhijit Poddar, ‘E-learning’ of select topics in solid state physics and quantum mechanics)
Some of the x-rays bounce onto a film plate. This makes an image.
We end up with a diffraction pattern on film.
Figure 11.4, Purves’s Life: The Science of Biology, 7th Edition
Once we have a diffraction pattern, we use math to work backwards:
We figure out where the atoms must have been.
The result is an electron density map.
This traces out the shape of the atoms in the molecule.
Left image: X-ray diffraction pattern, Wikimedia. Right upper image: electron density map. Right lower image: model fitting atoms to the density map.
Appearance of a zone of the electron density map of a protein crystal, before it is interpreted
The same electron density map after its interpretation in terms of a peptidic fragment.
These last two images come from CSIC Crystallography
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External resources
Welcome to the world of Crystallography: The Spanish National Research Council
Cryo Electron Microscopy
Cryo-EM is an electron microscopy (EM) technique applied on samples cooled to cryogenic temperatures and embedded in an environment of vitreous water.
An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane.
While development of the technique began in the 1970s, recent advances in detector technology and software algorithms have allowed for the determination of biomolecular structures at near-atomic resolution.
This has attracted wide attention to the approach as an alternative to X-ray crystallography or NMR spectroscopy for macromolecular structure determination without the need for crystallization.
Cryo-electron microscopy wins chemistry Nobel, Nature
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Unmasking mask myths
We are living in an era of a viral pandemic, COVID-19, in which viral particles are spread through the air from one person to another.
Numerous scientific studies show that if most people even simple cloth face masks while near each other, this dramatically reduced the viral particles in the air, and increases safety.
The effect of wearing masks is so effective that in areas where people follow social distancing & mask rules, the incidence of COVID is shrinking.
However, there has been a growing resistance to wearing a mask, fueled by conspiracy theories, pseudoscience, and Russian social media troll farms deliberately spreading misinformation.
Many of us have met individuals who claimed that face masks either “block oxygen from getting in” or “make us breathe carbon monoxide.” Both claims are literally impossible, yet widely believed.
If we have a student make such a claim, how can we turn this into a teachable moment?
https://www.facebook.com/groups/907893332705087/permalink/1547682505392830/
Addressing the carbon monoxide claim
Claim: “Masks traps our carbon monoxide and poison us.”
How to respond:
First, revisit the equation for cellular respiration. Note that this process doesn’t produce carbon monoxide!
from the Amoeba sisters
So if someone makes this claim then ask “Where does this carbon monoxide coming from?”
If they give a vague response ask them to clarify and back up their answer with a source.
Here’s another graphic showing cellular respiration
Addressing the “air can’t get through the mask” claim
Some people try to have it both ways: They claim that virus particles are so small that they can get through the mask
yet they also claim that the oxygen is too large to pass through the mask, so we (supposedly) get low oxygen and brain damage.
The obvious problem is that the virus particle is over 250 times larger than an oxygen molecule!
The covid molecule is 0.125 microns while an O2 molecule is only 0.0005 microns.
Also, to be clear, single viral particles don’t make people sick. The disease is only spread if people inhale multiple exhalation water-virus droplets,
Each droplet is thousands of times larger than a viral particle; each droplet has thousands of viral particles. It is these larger drops that masks are good at filtering.
Image created by Fusion Animation.
Addressing the low amount of oxygen claim
First off, even without a virus, your body automatically adapts to lower levels of oxygen in the air.
If that weren’t the case then anyone who visited a high altitude city like Denver, Colorado, would have died.
As we all know, up in Denver the air is thinner, so there are less O2 molecules per cubic meter of air. But we adjust, and as long as we don’t play NFL caliber football for an hour, we’re just fine.
The other claim is that these face masks “trap our breath” preventing us from getting oxygen, so that our O2 blood levels fall.
Yet see for yourself – masks don’t do that!
Photo credit. Dr. Megan Hall
Dr. Megan Hall writes:
Below is me in 4 scenarios. I wore each mask for 5 minutes and checked my oxygen saturation (shown as the percentage below) along with my heart rate (HR, in beats per minute) using noninvasive pulse oximetry.
Keep in mind, immediately prior to this, I had been wearing the surgical mask for 5 hours.
Results:
No mask: 98%, HR 64
Surgical mask: 98%, HR 68
N95 mask: 99%, HR 69
N95 plus surgical mask (which is how most healthcare providers are wearing masks): 99%, HR 69.
Finally, if “breathing in your own breath is dangerous” then
* how come it is perfectly safe to perform CPR with mouth to mouth resuscitation?
* how come it is safe to kiss?!
The air that a person exhales has more than enough O2 to keep someone else alive.
How well do masks work?
Masks don’t need to stop all droplets. COVID is dangerous not because some particles are airborne (thats true for tons of viruses) but because
(a) it transmits more easily,
and (b) causes more damage.
When we reduce the number of droplets released, then the spread of covid significantly decreases.
Here is a video from Dr. Joe Hanson, from “It’s ok to be smart.” It is an awesome, slow-motion schlieren imaging experiment that demonstrates why masks work.
How Well Do Masks Work? (Schlieren Imaging In Slow Motion!)
References for “How Well Do Masks Work?”
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We’re not using umbrellas as they were originally intended – https://qz.com/quartzy/1707271/americans-are-not-using-umbrellas-as-they-were-intended/
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World Health Organization – Q&A about masks https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/q-a-on-covid-19-and-masks
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American Society for Microbiology – COVID-19 Transmission Dynamics
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Oran, Daniel P., and Eric J. Topol. “Prevalence of Asymptomatic SARS-CoV-2 Infection: A Narrative Review.” Annals of Internal Medicine (2020). https://doi.org/10.7326/M20-3012
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Chu, Derek K., et al. “Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis.” The Lancet (2020). https://doi.org/10.1016/S0140-6736(20)31142-9
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Dhama, Kuldeep, et al. “Coronavirus disease 2019–COVID-19.” Clinical Microbiology Reviews (2020) https://cmr.asm.org/content/33/4/e00028-20
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Stadnytskyi, Valentyn, et al. “The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission.” Proceedings of the National Academy of Sciences 117.22 (2020): 11875-11877. https://doi.org/10.1073/pnas.2006874117
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Cheng, Vincent CC, et al. “The role of community-wide wearing of face mask for control of coronavirus disease 2019 (COVID-19) epidemic due to SARS-CoV-2.” Journal of Infection (2020). https://doi.org/10.1016/j.jinf.2020.04.024
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Eikenberry, Steffen E., et al. “To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic.” Infectious Disease Modelling (2020). https://doi.org/10.1016/j.idm.2020.04.001
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Greenhalgh, Trisha, et al. “Face masks for the public during the covid-19 crisis.” Bmj 369 (2020). https://doi.org/10.1136/bmj.m1435
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Cheng, Kar Keung, Tai Hing Lam, and Chi Chiu Leung. “Wearing face masks in the community during the COVID-19 pandemic: altruism and solidarity.” The Lancet (2020). https://doi.org/10.1016/S0140-6736(20)30918-1
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Davies, Anna, et al. “Testing the efficacy of homemade masks: would they protect in an influenza pandemic?.” Disaster medicine and public health preparedness 7.4 (2013): 413-418. https://dx.doi.org/10.1017%2Fdmp.2013.43
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pH diets, health, and homeostasis
Students need to be aware of pseudoscience diets. Some of these claim that by eating more acidic or basic foods you can change your body’s pH level, and thus treat disease.
Not only is this entire idea incorrect, if a person does change their pH beyond even a tiny bit then they will almost immediately die. Changing one’s body pH is almost impossible, but when it happens it is fatal,
What are acids and bases? Acids are bases are complimentary types of chemicals. Acids perform one kind of chemical reaction; bases perform the opposite action. Learn more here about acids and bases.
Here’s the critical point: When it comes to living, what matters is whether acids and bases are working in a safe balance. Cells only work correctly in a very narrow range of conditions.
Too much or too little of any molecule, and they begin to malfunction or die. Homeostasis is the body’s way of keeping chemicals in a safe, dynamic balance.
Alkaline Diet, SkepDic
Alkaline Diet, RationalWiki
pH Mythology: Separating pHacts from pHiction
Alkaline Water Surges Despite Lack of Evidence
Alkaline food, McGill University
Chemistry lesson for The Food Babe… and everyone else #19: Alkaline Diets Do Not Cure Disease, McGill University
Physics Hanukkah Fun
A goal of Social Studies is to expose students to the diversity of ethnic, religious, and cultural observances in our world. The College, Career, and Civic Life (C3) Framework for Social Studies State Standards notes that students should be able to describe how religions are embedded in culture and cannot only be isolated to the “private” sphere, and identify which religious communities are represented or obscured in public discourse.
A goal of science education is to see how basic laws of nature allow us to understand all phenomenon in our physical universe, from the simplest (fire and candles) to the most complex (how stars work.)
During the holiday season many science teachers do something fun on the physics of Christmas (Google that; thousands of results.) Yet there are more religions than Christianity and more phenomenon related to holidays. In the spirit of science and multiculturalism here we can look at the physics and chemistry of Hanukkah.
What is Hanukkah about?
Hanukkah is a minor Jewish holiday. It doesn’t come from the Hebrew Bible but instead from the book of Maccabees, part of the Jewish apocrypha. It is also known as Hag ha’urim, the Festival of Lights.
Hanukkah is a Hebrew word meaning “dedication.” It refers to the eight-day celebration during which Jews commemorate the victory of the Maccabees over the Hellenistic Syrians in 165 B.C.E. and the subsequent rededication of the Temple in Jerusalem. Hanukkah is specifically about countering antisemitism and was the first successful war for religious freedom.
Celebrations center around the lighting of the hanukkiyah (menorah,) foods prepared in oil, including latkes (potato pancakes) and sufganiyot (jelly doughnuts), songs and games. – Intro to Hanukkah
The Hebrew name Maccabee means “hammer”, and referred first to a leader of the revolt, Judas, the third son of Mattathias.
Capillary action
During the holiday Jewish people light a Chanukah menorah מנורת חנוכה, also called a Ḥanukiyah חַנֻכִּיָּה.
The wick is above the oil, drawing fluid up the wick through capillary action. What exactly is capillary action?
Capillary action & molecule forces
Oil is drawn up through capillary action, also called wicking.
This is a tale of two competing forces:
There is an adhesive force between the oil molecules and the cotton molecules.
And there is an intermolecular/cohesive force between the oil molecules.
Cohesion = ability of like molecules to stick together
Adhesion = ability of dissimilar molecules to stick together
from Bioninja
When the adhesion force > cohesion force then the oil molecules are slowly pulled into the wick.
From Hyperphysics, Surface tension
The following explanation is adapted from the discussion by Sean Snider, on Quora.
A fluid such as heating oil will tend to flow upwards against gravity due to capillary motion.
The individual atoms in the oil will interact with the fiber atoms to cause adhesion.
The oil atoms will bump into the fiber atoms – and move upwards due to intermolecular forces.
The difference in charge between the two types of atoms causes them to repel in all directions, including up.
The oil atoms will keep moving up – unless the forces between them cause them to clump together so that intermolecular forces weaken.
In that case their collective mass is too much to repel the force of gravity.
Typically the density of the fiber itself prevents the oil particles from clumping enough to reach this threshold. Thus they continue to move upward.
This allows the oil to reach the top of the wick and burn.
Instead of the fiber burning quickly, the oil burns.
(Some of the fiber also burns, but much less quickly.)
Capillary action student activities
Wick lab/game! sciensation.org
Capillary action and diffusion lab
Lights, Camera, (Capillary) Action! Scientific American
Convection & temperature differentials
The heat from the flame warms up the small olive oil vessels, below.
Those vessels are often transparent.
That heat causes a temperature differential: warmer oil at the top and cooler oil at the bottom.
This would cause convection and/or turbulence in the fluid.
This should be visible if we record it with a high speed, high-resolution smartphone camera.
Convection, turbulence, and related topics are usually left out of high school physics curriculum, so this might be a fun way to introduce it.
Experiment: Add a drop of coloring into oil. Light the wick.
Then we can visually observe the convection currents.
Dreidel physics
A dreidel (Yiddish: דרײדל) or sevivon (Hebrew: סביבון) is a four-sided spinning top, played by children during the Jewish holiday of Hanukkah. Contrary to popular belief, this toy is not part of the Hanukkah story. It is a Jewish variant on the teetotum, a gaming toy found in many European cultures.
Through use and observation of a dreidel students may be inspired to understand how it works, which requires knowledge of angular momentum, rotational motion, gyroscopes, and precession.
One idea for class use is to record the motion with a high speed camera, and then play the footage back in slow motion, to reveal details of motion that would not be clearly visible to the naked eye.
Let’s take a look at Extreme High-Speed Dreidel Physics by Alexander R. Klotz:
… a dreidel is an example of a spinning top, a source of extremely difficult homework problems in undergraduate classical mechanics related to torque and angular momentum and rigid body motion and whatnot. I was chatting with a theorist I know who mentioned that it would be fun to calculate some of these spinning-top phenomena for the dreidel’s specific geometry (essentially a square prism with a hyperboloid or paraboloid base), and I suggested trying to compare it to high-speed footage [1000 frames per second] ….
Check out the article and videos here.
Related dreidel topics to investigate
What keeps spinning tops upright? Ask a Mathematician/Physicist
What is precession? It is a change in the orientation of the rotational axis of a rotating body. In geometry we would say that if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis.
Precession (Wikipedia)
Dreidels also follow the law of conservation of angular momentum. We learn more about that in Angular momentum
And a dreidel itself is similar to a gyroscope.
The statistics of dreidel motion
Are dreidels fair? In other words, does the average dreidel have an equal chance of turning up any one of its four sides? Dreidel Fairness Study
Ultra High Speed Physics.
You’re not a mad scientist unless you ask questions like “Imagine a game of dreidel with a 60-billion-RPM top….” Focus: The Fastest Spinners. APS Physics
How is the holiday spelled? ELA connections
Why write “Hanukkah” instead of “Chanukah” – surely one spelling is right and the other is wrong? The reason for the spelling confusion is the limitations of the English alphabet. Hanukkah is a Hebrew word (חנוכה)
That first Hebrew letter of this word, ח , has a guttural sound. This sound used to exist in ancient English but doesn’t exist in modern English. The modern pronunciation of this letter is a voiceless uvular fricative (/χ/)
As such there is no one correct-and-only way to transliterate this letter. Over the past 2 centuries four ways have developed:
KH – Khanukah (used in old fashioned translations of Yiddish)
CH – Chanukah
H – Hanukkah (the extra ‘k’ is added just to make it 8 letters long.)
H – Ḥanukah (notice the H with a dot under it.)
Each of these is equally valid.
History, art, and social justice connections
Hanukkah and the Maccabees have been a common theme in classical Christian art, sculpture, and music. The story of the Maccabees is a part of Western Civilization through both Jewish and Christian culture. In this article one can see the art, music, and sculpture of Hanukkah.
On a related social justice note, a big part of being anti-racist is listening to voices. Make space to learn from the lived experiences of our students, their families, and their communities. As such I would like to share this:
Hanukkah is about countering antisemitism: Be aware of Hanukkah Erasure.
Learning Standards
College Board Standards for College Success in Science
ESM-PE.1.2.1 Describe and contrast the processes of convection, conduction and radiation, and give examples of natural phenomena that demonstrate these processes.
ESM-PE.1.2.1c Use representations and models (e.g., a burning candle or a pot of boiling water) to demonstrate how convection currents drive the motion of fluids. Identify areas of uneven heating, relative temperature and density of fluids, and direction of fluid movement.
Next Generation Science Standards
MS-PS1-4. Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
Massachusetts Science and Technology/Engineering Curriculum Framework
7.MS-PS3-6 (MA). Use a model to explain how thermal energy is transferred out of hotter regions or objects and into colder ones by convection, conduction, and radiation.
College, Career, and Civic Life (C3) Framework for Social Studies State Standards
College, Career, and Civic ready students:
D2.Rel.4.9-12: Describe and analyze examples of how religions are embedded in all aspects of culture and cannot only be isolated to the “private” sphere.
D2.Rel.12.9-12: Identify which religious individuals, communities, and institutions are represented in public discourse, and explain how some are obscured.
Transliteration of Hebrew letters
Library of Congress (USA) ALA-LC Romanization Tables
Gay-Lussac’s law (Amontons’ law)
from the NASA Glenn Research Center website
Gases have various properties that we can observe with our senses, including the gas pressure, temperature (T), mass, and the volume (V) that contains the gas.
Careful, scientific observation has determined that these variables are related to one another and that the values of these properties determine the state of the gas.
The relationship between temperature and volume, at a constant number of moles and pressure, is called Charles and Gay-Lussac’s Law in honor of the two French scientists who first investigated this relationship.
Charles did the original work, which was verified by Gay-Lussac.
They observed that if the pressure is held constant, the volume V is equal to a constant times the temperature T:
V = constant * T
For example, suppose we have a theoretical gas confined in a jar with a piston at the top. The initial state of the gas has a volume qual to 4.0 cubic meters, and the temperature is 300 Kelvin.
With the pressure and number of moles held constant, the burner has been turned off and the gas is allowed to cool to 225 Kelvin. (In an actual experiment, a cryogenic ice-bath would be required to obtain these temperatures.)
As the gas cools, the volume decreases to 3.0 cubic meters.
The volume divided by the temperature remains a constant (4/300 = 3/225 ).
Here is a computer animation of this process:
Examples of where this occurs in real life
TBA
and
Please note, like all the other gas laws, this is not a law of physics. Rather, this is a generally useful rule, but only valid when gas temperature and pressure is low enough for the atoms to usually be far apart from each other.
As we deal with more extreme cases, this rule doesn’t hold up.
Avogadro’s law
Previously in Chemistry one has learned about Avogadro’s hypothesis:
Equal volumes of any gas, at the same temperature and pressure, contain the same number of molecules.
Reasoning
(from Modern Chemistry, Davis, HRW)
In 1811, Avogadro found a way to explain Gay-Lussac’s simple ratios of combining volumes without violating Dalton’s idea of indivisible atoms. He did this by rejecting Dalton’s idea that reactant elements are always in monatomic form when they combine to form products. He reasoned that these molecules could contain more than one atom.
Avogadro also put forth an idea known today as Avogadro’s law: equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
It follows that at the same temperature and pressure, the volume of any given gas varies directly with the number of molecules.
Avogadro’s law also indicates that gas volume is directly proportional to the amount of gas, at a given temperature and pressure.
Note the equation for this relationship.
V = kn
Here, n is the amount of gas, in moles, and k is a constant.
Avogadro’s reasoning applies to the combining volumes for the reaction of hydrogen and oxygen to form water vapor.
Dalton had guessed that the formula of water was HO, because this formula seemed to be the most likely formula for such a common compound.
But Avogadro’s reasoning established that water must contain twice as many H atoms as O atoms, consistent with the formula H2O.
As shown below, the coefficients in a chemical reaction involving gases indicate the relative numbers of molecules, the relative numbers of moles, and the relative volumes.
The simplest hypothetical formula for oxygen indicated 2 oxygen atoms, which turns out to be correct. The simplest possible molecule of water indicated 2 hydrogen atoms and 1 oxygen atom per molecule, which is also correct.
Experiments eventually showed that all elements that are gases near room temperature, except the noble gases, normally exist as diatomic molecules.
As an equation
Avogadro’s Law – also known as Avogadro–Ampère law
when temperature and pressure are held constant:
volume of a gas is directly proportional to the # moles (or # particles) of gas
n1 / V1 = n2 / V2
or
What does this imply?
As # of moles of gas increases, the volume of the gas also increases.
As # of moles of gas is decreased, the volume also decreases.
Thus, # of molecules (or atoms) in a specific volume of ideal gas is independent of their size (or molar mass) of the gas.
Important! This is not a law of physics!
Rather, this is a generally useful rule, which is only valid when gas temperature and pressure is low enough for the atoms to usually be far apart from each other. As we begin to deal with more extreme cases, this rule doesn’t hold up.
At what point does Avogadro’s law not apply?
Example problems
These problems are from The Chem Team, Kinetic Molecular Theory and Gas Laws
Example #1: 5.00 L of a gas is known to contain 0.965 mol. If the amount of gas is increased to 1.80 mol, what new volume will result (at an unchanged temperature and pressure)?
Solution:
I’ll use V1n2 = V2n1
(5.00 L) (1.80 mol) = (x) (0.965 mol)
x = 9.33 L (to three sig figs)
Example #2: A cylinder with a movable piston contains 2.00 g of helium, He, at room temperature. More helium was added to the cylinder and the volume was adjusted so that the gas pressure remained the same. How many grams of helium were added to the cylinder if the volume was changed from 2.00 L to 2.70 L? (The temperature was held constant.)
Solution:
1) Convert grams of He to moles:
2.00 g / 4.00 g/mol = 0.500 mol
2) Use Avogadro’s Law:
V1 / n1 = V2 / n2
2.00 L / 0.500 mol = 2.70 L / x
x = 0.675 mol
3) Compute grams of He added:
0.675 mol – 0.500 mol = 0.175 mol
0.175 mol x 4.00 g/mol = 0.7 grams of He added
Example #3: A balloon contains a certain mass of neon gas. The temperature is kept constant, and the same mass of argon gas is added to the balloon. What happens?
(a) The balloon doubles in volume.
(b) The volume of the balloon expands by more than two times.
(c) The volume of the balloon expands by less than two times.
(d) The balloon stays the same size but the pressure increases.
(e) None of the above.
Solution:
We can perform a calculation using Avogadro’s Law:
V1 / n1 = V2 / n2
Let’s assign V1 to be 1 L and V2 will be our unknown.
Let us assign 1 mole for the amount of neon gas and assign it to be n1.
The mass of argon now added is exactly equal to the neon, but argon has a higher gram-atomic weight (molar mass) than neon. Therefore less than 1 mole of Ar will be added. Let us use 1.5 mol for the total moles in the balloon (which will be n2) after the Ar is added. (I picked 1.5 because neon weighs about 20 g/mol and argon weighs about 40 g/mol.)
1 / 1 = x / 1.5
x = 1.5
answer choice (c).
Example #4: A flexible container at an initial volume of 5.120 L contains 8.500 mol of gas. More gas is then added to the container until it reaches a final volume of 18.10 L. Assuming the pressure and temperature of the gas remain constant, calculate the number of moles of gas added to the container.
Solution:
V1 / n1 = V2 / n2
| 5.120 L | 18.10 L | |
| –––––––– | = | –––––– |
| 8.500 mol | x |
x = 30.05 mol <— total moles, not the moles added
30.05 – 8.500 = 21.55 mol (to four sig figs)
Notice the specification in the problem to determine moles of gas added. The Avogadro Law calculation gives you the total moles required for that volume, NOT the moles of gas added. That’s why the subtraction is there.
.
Charles’s Law
Here we learn about Charles’s Law (also known as Charles and Gay-Lussac’s Law.)
What does it do? It describes how gases tend to expand when they are heated.
This is an example of algebra in the real world:
A gas’s volume is proportional to its temperature.
(This is only true when measuring temperature on an absolute temperature scale.)
In algebra, this relationship can be written as:
-> Gas expands as the temperature increases
-> Gas contracts as the temperature decreases
This relationship can be written as:
Important! This is not a law of physics!
Rather, this is a generally useful rule, which is only valid when gas temperature and pressure is low enough for the atoms to usually be far apart from each other.
As we begin to deal with more extreme cases, this rule doesn’t hold up.
Let’s see this in action!
Origin
Named after Jacques Alexandre César Charles (1746 – 1823) a French inventor, scientist, mathematician, and balloonist.
Just so we’re all clear on this, he was kind of a mad scientist. And I say that with the utmost approval!
Contemporary illustration of the first flight by Prof. Jacques Charles with Nicolas-Louis Robert, December 1, 1783. Viewed from the Place de la Concorde to the Tuileries Palace (destroyed in 1871)
Apps
Charles’s law app
Learning standards
Massachusetts Science and Technology/Engineering Curriculum Framework
8.MS-PS1-4. Develop a model that describes and predicts changes in particle motion, relative spatial arrangement, temperature, and state of a pure substance when thermal energy is added or removed.
Next Generation Science Standards
MS-PS1-4. Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
College Board Standards
Objective C.1.5 States of Matter
C-PE.1.5.2 Explain why gases expand to fill a container of any size, while liquids flow and spread out to fill the bottom of a container and solids hold their own shape. Justification includes a discussion of particle motion and the attractions between the particles.
C-PE.1.5.3 Investigate the behavior of gases. Investigation is performed in terms of volume (V ), pressure (P ), temperature (T ) and amount of gas (n) by using the ideal gas law both conceptually and mathematically.
Common Core Math
Analyze proportional relationships and use them to solve real-world and mathematical problems.
CCSS.MATH.CONTENT.7.RP.A.2
Recognize and represent proportional relationships between quantities.
CCSS.MATH.CONTENT.7.RP.A.2.A
Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin.
CCSS.MATH.CONTENT.7.RP.A.2.B
Identify the constant of proportionality (unit rate) in tables, graphs, equations, diagrams, and verbal descriptions of proportional relationships.
Boyle’s law (gas laws)
A general relationship between pressure and volume: Boyle’s Law
As the pressure on a gas increases, the volume of the gas decreases because the gas particles are forced closer together.
Conversely, as the pressure on a gas decreases, the gas volume increases because the gas particles can now move farther apart.
Example: Weather balloons get larger as they rise through the atmosphere to regions of lower pressure because the volume of the gas has increased; that is, the atmospheric gas exerts less pressure on the surface of the balloon, so the interior gas expands until the internal and external pressures are equal.
from Libretexts, Chemistry, 5.3: The Simple Gas Laws: Boyle’s Law, Charles’s Law and Avogadro’s Law, CC BY-NC-SA 3.0.
This means that, at constant temperature, the pressure (P) of a gas is inversely proportional to the volume (V).
PV = c
Important! This is not a law of physics! Rather, this is a generally useful rule, which is only valid when gas temperature and pressure is low enough for the atoms to usually be far apart from each other. As we begin to deal with more extreme cases, this rule doesn’t hold up.
Let’s see the relationship in action, here:
from http://www.grc.nasa.gov/WWW/K-12/airplane/boyle.html
How was this general rule discovered?
Early scientists explored the relationships among the pressure of a gas (P) and its temperature (T), volume (V), and amount (n) by holding two of the four variables constant (amount and temperature, for example), varying a third (such as pressure), and measuring the effect of the change on the fourth (in this case, volume).
The history of their discoveries provides several excellent examples of the scientific method.
The Irish chemist Robert Boyle (1627–1691) carried out some of the earliest experiments that determined the quantitative relationship between the pressure and the volume of a gas. Boyle used a J-shaped tube partially filled with mercury.
In these experiments, a small amount of a gas or air is trapped above the mercury column, and its volume is measured at atmospheric pressure and constant temperature. More mercury is then poured into the open arm to increase the pressure on the gas sample.
The pressure on the gas is atmospheric pressure plus the difference in the heights of the mercury columns, and the resulting volume is measured. This process is repeated until either there is no more room in the open arm or the volume of the gas is too small to be measured accurately.
Details: Boyle’s Experiment Using a J-Shaped Tube to Determine the Relationship between Gas Pressure and Volume.
(a) Initially the gas is at a pressure of 1 atm = 760 mmHg (the mercury is at the same height in both the arm containing the sample and the arm open to the atmosphere); its volume is V.
(b) If enough mercury is added to the right side to give a difference in height of 760 mmHg between the two arms, the pressure of the gas is 760 mmHg (atmospheric pressure) + 760 mmHg = 1520 mmHg and the volume is V/2.
(c) If an additional 760 mmHg is added to the column on the right, the total pressure on the gas increases to 2280 mmHg, and the volume of the gas decreases to V/3
(This section from from Libretexts, Chemistry, 5.3: The Simple Gas Laws: Boyle’s Law, Charles’s Law and Avogadro’s Law, CC BY-NC-SA 3.0)
Learning standards
Massachusetts Science and Technology/Engineering Curriculum Framework
8.MS-PS1-4. Develop a model that describes and predicts changes in particle motion, relative spatial arrangement, temperature, and state of a pure substance when thermal energy is added or removed.
Next Generation Science Standards
MS-PS1-4. Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
College Board Standards
Objective C.1.5 States of Matter
C-PE.1.5.2 Explain why gases expand to fill a container of any size, while liquids flow and spread out to fill the bottom of a container and solids hold their own shape. Justification includes a discussion of particle motion and the attractions between the particles.
C-PE.1.5.3 Investigate the behavior of gases. Investigation is performed in terms of volume (V ), pressure (P ), temperature (T ) and amount of gas (n) by using the ideal gas law both conceptually and mathematically.
Common Core Math
Analyze proportional relationships and use them to solve real-world and mathematical problems.
CCSS.MATH.CONTENT.7.RP.A.2
Recognize and represent proportional relationships between quantities.
CCSS.MATH.CONTENT.7.RP.A.2.A
Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin.
CCSS.MATH.CONTENT.7.RP.A.2.B
Identify the constant of proportionality (unit rate) in tables, graphs, equations, diagrams, and verbal descriptions of proportional relationships.
Oils
“Oil” is a general name for any kind of molecule which is
nonpolar
that just means that its electrons are evenly distributed
PHET Polar molecules app
liquid at room temperature
of course, it could become solid if cooled, or evaporate if heated
Molecule has one end which is hydrophobic and another end which is lipophilic
The hydrophobic end likes to stick to water molecules. But hates sticking to oils.
The lipophilic end likes to stick to oil molecules, but hates sticking to water,
Made with many C and H atoms
Oils are usually flammable. Here we see oils in an orange skin interacting with a candle.
KaiserScience 