Category: Chemistry

Smelling Feet or Smelly Feet?

3/7/2023

Dorothy Hinshaw Patent
Nature’s Animal Ambassador

Do your feet sometimes smell rotten? Do you wish you could toss out your shoes and start with a new pair? We make jokes about smelly feet, but smell and feet have a very different relationship among some insects.

Take butterflies. Have you ever watched a butterfly flit over a plant, gently touch its feet to a leaf, and then fly on to the next leaf? That butterfly isn’t being picky about where to land. It’s hunting for the right kind of leaf for laying its eggs. It’s “smelling” the leaf with its feet!

Actually, we need to qualify that statement a bit. Some writers will say the insect is “smelling” the leaf while others may write that it’s “tasting” the leaf. Smelling and tasting are forms of “chemoreception,” or sensing of chemicals. Smell usually refers to sensing from a distance while tasting generally means actually touching the nerve cells that sense a chemical.

We humans have cells in our noses that send messages to our brains about chemicals in the air. We call that our sense of smell. We have cells on our tongues that sense chemicals dissolved in liquid in our mouths. That’s taste.

That butterfly doesn’t have a nose, and its mouth is a long tube for sucking up nectar from flowers. Its chemoreceptors are elsewhere, like on its feet, around its mouth, and on its antennae. Most butterflies lay their eggs on the plants that the hatched caterpillars will eat. Some species are very specific about what plants their young can feed on. Take the postman butterfly, which lives in Central and South America. Its caterpillars can only survive on certain species of passionflower vines. Other species are poisonous to their offspring.

The female postman butterfly has dozens of special nerve cells on her feet called “gustatory sensilla.” Scientists think that when she touches gently down on a leaf, these cells can sense chemicals there that would be poisonous to her caterpillars. She avoids laying eggs on those leaves. But when she finds a plant that will nourish her young, she’ll alight and lay her eggs.

Now take your shoes off and move your feet around on the floor. The only nerve endings on your feet are ones that sense touch. But then, you don’t need to be able to smell the ground you walk on. Imagine how gross it would be if your feet could smell the insides of your socks and shoes—yuck!

In these photographs taken through a microscope, you can see the sensory sensilla (arrow) on the feet of the female butterfly on the right, which the male on the left doesn't have. From PLoS Genet. Jul 2013; 9(7): e1003620.

Above: Postman butterfly feeding Right: Female postman butterfly laying an egg. As you can see from these two photos, the postman butterfly can have a variety of color patterns. From Heliconius.org

A dog’s nose is 300 times more powerful than a human nose, so it’s no wonder that dogs use their incredibly advanced sense of smell to do some very important jobs. In Super Sniffers, Dorothy Hinshaw Patent explores the various ways specific dogs have put their super sniffing ability to use: from bedbug sniffers to explosive detectors to life-saving allergy detectors . . . and more. This dynamic photo-essay includes first-hand accounts from the people who work closely with these amazing dogs. For more information, click here.

Dorothy Hinshaw Patent is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Patent, Dorothy Hinshaw. "Smelling Feet or Smelly Feet?" Nonfiction Minute, iNK
Think Tank, 23 Jan. 2018, www.nonfictionminute.org/the-nonfiction-minute/
Smelling-Feet-or-Smelly-Feet.

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In Praise of Vultures

1/24/2023

1 Comment

Stephen R. Swinburne
Lifelong naturalist

I really like vultures. Sure, they’re ugly and they eat nasty dead things. But those are not necessarily bad characteristics.

First let’s deal with “ugly.” Vultures’ bald heads are what make them seem ugly to most people. But think about why they’re bald. Imagine thrusting your head inside the carcass of a white-tailed deer to reach the meat. A feathered head might capture bits of flesh, blood and gore and you end up with a face full bacteria and flies. Scientists believe that one reason vultures have evolved featherless heads is to aid in hygiene. A bald head stays clean and any remaining germs or bacteria are baked off by the sun. Vultures have also found that a bald head can help with temperature regulation. When it gets cold they can tuck their heads down to keep their neck covered with feathers. When it’s hot, vultures can extend their neck to expose bare skin. Their bald heads work so well that I wrote a poem about them.

Naked Head

It’s best to have no feathers,

When you stick your head in guts,

That way you don’t go walkin’ round,

Your noggin dripping schmutz.

Moving on to “eating nasty dead things,” the next time you see vultures eating a dead animal on the side of the road, be thankful! That carcass might be dead from rabies or contaminated with other harmful diseases. Vultures have the amazing ability to consume rotting and diseased flesh and stay healthy. It’s all in the stomach. Vultures possess very powerful stomach acids that destroy most bacteria and deadly viruses. In fact, vulture stomach acid is so strong it can dissolve metal! Except if that metal is lead shot -- many turkey vultures are killed every year by consuming shot that they encounter in dead deer. Vultures are the world’s natural “sanitation workers,” helping to stop the spread of disease.

I’m so appreciative of the work they do, I even wrote a poem about eating dead things:

Dead Meat

I like my meat dead,

It’s best if it’s not moving.

Don’t want to see one final twitch,

I prefer it oozing

So, the next time you see a vulture circling in the noonday sky, think about the valuable and important clean up service this bird provides to us and to the environment. Maybe I’ll write a poem about that….

Two magnificent specimens: at right, a turkey vulture showing off his bald head and ,above, an even balder American black vulture. Wikimedia Commons

My friends the black vultures didn't kill this deer. They are just going to be cleaning up the carcass. Wikipedia commons. Photo by Nathaniel Paluga.

Steve Swinburne is a science writer, but as you can see from this Minute, he likes to write poetry too. In his book Ocean Soup, he offers verses in the voices of tide-pool animals, including the barnacle, sea urchin, sculpin, mussel, starfish, hermit crab, anemone, and lobster. For more about Steve's poetry, click here.

Steve Swinburne is a member of iNK's Authors on Call and is available for classroom programs through FieldTripZoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Swinburne, Stephen R. "In Praise of Vultures." Nonfiction Minute, iNK Think Tank, 8 Dec. 2017, www.nonfictionminute.org/ In-Praise-Of-Vultures.

1 Comment

How to Extinguish a Fire with a Bag of Potato Chips

1/10/2023

2 Comments

Vicki Cobb

The Master Chef of Kids' Hands-on Science

Ever taste a stale potato chip? If not, here’s how to make one:

If you have an open bag of potato chips lying around, you can use them. Otherwise open a new bag.
Put a few fresh potato chips in a glass bowl in the sunlight and wait a day or two.
Taste one of these exposed potato chips.
Compare it to the taste of a chip from a brand new bag.

Big difference, no? It’s enough to worry a potato chip manufacturer. There are two things that make a potato chip stale. Can you guess what they are? Okay, I’ll tell you: Air (specifically oxygen in the air) and light. So potato chip manufacturers know that if they want to keep their chips fresh, they have to remove oxygen and light. How do they do that?

Take a close look at an opened bag of potato chips. It is foil-lined to make it light proof. An unopened bag is very puffy because it is filled with a gas. This puffiness protects the chips from breaking. But the gas in the bag is not air, which is a mixture of about 20% oxygen and 79% nitrogen. It is air without the oxygen, so it’s mostly nitrogen.

You can prove this. Oxygen is needed for fire to burn. If the air around a flame is flooded with nitrogen, the flame goes out. So you can use the gas in a bag of potato chips to put out a candle. Here’s how:

Light a candle. (Make sure you have an adult help you since this trick involves fire.)
Cut off the corner of a new bag of potato chips.
Gently squeeze some of the gas from the potato chip bag near the candle flame. If you squeeze too hard, it’s like blowing the flame out. You want it to go out because the nitrogen in the potato chip bag is quietly flowing into the space around the flame.

Now you know how to extinguish a flame with a bag of potato chips. You have also proved that there is no oxygen in a potato chip bag! And you know why!

Now go educate some grown-up.

Before being flooded with nitrogen

After being flooded with nitrogen

Vicki Cobb’s best known book is Science Experiments You Can Eat. This is the new third revision published in 2016.

Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Cobb, Vicki. "How to Extinguish a Fire with a Bag of Potato Chips." Nonfiction Minute, iNK Think Tank, 2 Oct. 2017, www.nonfictionminute.org/the-nonfiction-minute/how-to-extinguish-a-fire-with-a-bag-of-potato-chips.

2 Comments

Some Painful Truth

10/24/2022

1 Comment

Vicki Cobb
The Master Chef of Kids' Hands-on Science.

How well do you handle spicy food? Do you find food with a “kick” eye-watering and difficult to swallow? Or are you a real “fire eater;” nothing can be too hot?

A scientist, named Wilbur Scoville, figured out how to rank spicy food for hotness in 1912. The “heat” from peppers comes from a chemical called capsaicin (cap-say-sin). Pure capsaicin registers 16 million heat units on the Scoville scale. Zero is a sweet green, red or yellow pepper. A fresh, green Jalapeño (ha-la-pen-yo) is rated 2,500-8,000 units, a lot less hot than pure capsaicin.

The fact is that you don’t “taste” the heat. The sensation of heat comes from nerve endings in your tongue that respond to pain. Of course, these nerve endings are not just in your tongue. They are all over your body. So a good scientific question is: Can you “taste” hot sauce with, say, your wrist?

Check it out. Rub the inside of your wrist with a cut Jalapeño pepper or some hot sauce. Wait a few minutes. Feel the burn? Rinse off your wrist well with cool water.

Your tongue, of course, is much more sensitive than your wrist to many chemicals because it is always wet. Capsaicin, like a lot of other chemicals dissolves in water and reaches those nerve endings more quickly.

Another liquid that triggers your pain nerves in your tongue is soda. The carbon dioxide in the bubbles reacts with an enzyme in your mouth to form a weak chemical called carbonic acid. This acid fires the pain nerve endings in your tongue giving soda its “bite.”

How well can you tolerate this pain? Stick your tongue into a freshly opened glass of soda and hold it there. See how long you can keep it in the drink. One minute? Two minutes? Most people can’t last a minute. But maybe you’re tougher than that.

Some Mexican parents give their kids mixtures of sugar and red chili powder when they’re little to build up their tolerance for spicy foods. Do you think that people who love spicy food could also be champions at keeping their tongues immersed in soda? Design an experiment to find out at your next party.

Hot Stuff from Vicki Cobb on Vimeo.

atonguelashing from Vicki Cobb on Vimeo.

These videos were made from Vicki Cobb’s book We Dare You! She invites you to join her video project and make your own videos from her book and post them on the www.wedareyouvideos.com website.

Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Cobb, Vicki. "Some Painful Truth." Nonfiction Minute, iNK Think Tank, 17 Oct. 2017, www.nonfictionminute.org/the-nonfiction-minute/some-painful-truth.

1 Comment

Why You Can’t Defrost a Salad…Yet

5/2/2022

0 Comments

Vicki Cobb
The Master Chef of Kids' Hands-on Science

At left in the back is a fresh spinach leaf that has been treated with trehalose, frozen and defrosted.. The droopy one has been frozen and defrosted without trehalose. It's what is giving us hope that we may soon be able to defrost a salad.

When it comes to preserving a fresh taste in food to be eaten at some later time, nothing beats freezing it. That was the discovery made by Clarence Birdseye in 1924. He had been working in northern Canada and noticed that fish caught by the native Canadian Inuits froze almost instantly in the frigid winter air. It was just as delicious when cooked and eaten months later as it was on the day it was fresh. Birdseye figured that if food was frozen quickly at very cold temperatures, large ice crystals couldn’t form to damage the food and make it mushy. His flash-freezing process made him very rich.

The problem isn’t so much the freezing of food as what happens when it’s defrosted. See for yourself. Stick a stalk of celery in your freezer. The next day defrost it. Want to eat it? Compare it to a fresh unfrozen stalk. The perky structure of fresh celery is destroyed by ice. Water has the very unusual property of expanding and taking up more space when it changes into ice than when in a liquid state. That’s why ice cubes float and frozen unopened soda cans bulge.   Expanding ice crystals destroy the cell walls of plants. Quickly freezing fresh food keeps the ice crystals smaller than slower freezing, but they are still large enough to destroy the cell walls of delicate vegetables like spinach or lettuce. But if you defrost frozen spinach from the supermarket it is beyond limp. So a salad you can defrost and serve as if it were fresh has seemed like an impossible dream.

Federico Gomez, a Swedish scientist, is working to change this. Like Birdseye he took a close look at nature, specifically at plants that stay alive in very cold climates. He discovered that they contain a sugar called trehalose (tree-HAL-ose) that works like a natural antifreeze. Could he find a way to get trehalose into spinach leaves? If so, would the trehalose protect the structure of the spinach and keep it crisp after defrosting? This picture shows the results. The leaf on the left was treated with trehalose. The one on the right was untreated. He froze and defrosted both. The treated leaf is as crisp as if it had never been frozen!

Just because there is success in a lab doesn’t mean a defrosted salad will show up on your dinner plate any time soon. But these results are enough to keep the research going.

Move over Clarence Birdseye!

This is a nice fresh, crisp piece of celery...

...and this is the same piece of celery after being frozen and then defrosted. Yuk!

Cobb has revised her classic book, Science Experiments You Can Eat. While doing her research, she came across this work of Frederico Gomez. She bought trehalose on line and soaked some slices of parsnip and zucchini in a trehalose solution, hoping that the sugar would be absorbed by the plant cells. But when she froze them and defrosted them, it didn't work. Dr. Gomez got the sugar inside the plant cells by removing some water from between the cells in a vacuum chamber, soaking the leaves in a trehalose solution (which moved the sugar into the spaces outside the cells) and then exposing the leaves with a mild electric shock to get the sugar through the cell walls. Vicki didn't have the equipment to do all this but she tried anyway. The book was published in 2016.

Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Cobb, Vicki. "Why You Can't Defrost a Salad...Yet." Nonfiction Minute, iNK Think
Tank, 11 01 2018, www.nonfictionminute.org/the-nonfiction-minute/
Why-You-Can't-Defrost-a-Salad-Yet.

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Smelling Feet or Smelly Feet?

In Praise of Vultures

How to Extinguish a Fire with a Bag of Potato Chips

Some Painful Truth

Why You Can’t Defrost a Salad…Yet

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