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​Cool Chemistry

Disappearing Gum

10/26/2021

1 Comment

 
What happens if you chew gum and chocolate at the same time?  You'll find out in this sweet candy science experiment while learning an important concept in chemistry: solubility.
Click and expand the tabs below to get started
What you'll need
  • Chewing gum - candy coated pieces like gum-balls or Chiclets are best, but any stick or piece of bubblegum will work.
  • Chocolate - milk chocolate like Hershey's Kisses or plain Halloween-sized candy bars are best.
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experimental procedure
  1. Chew the gum in your mouth for a minute or two.
  2. Take the gum out of your mouth (yes, really) and compare how it looks now compared to  how it looked before you chewed it.
  3. Put the gum back in your mouth, then also put a piece of chocolate in your mouth and chew them together. 
  4. After another minute or two take the gum (and any chocolate that may be left) out of your mouth.  What does it look like now?  Is it still sticky?
  5. Put it back in your mouth and keep chewing.  What happens to the gum?  If you have more chocolate add that to your mouth and continue chewing.  Can you make the gum disappear?

what's happening
This is a chemistry experiment, even though you are doing it in your mouth! It illustrates a very important concept in chemistry called solubility, which is the ability of one substance to dissolve another substance.  Chemists say that “like dissolves like” and this is an example of that.  If your gum was candy coated, like a Chiclet or gum-ball, you should have noticed that the candy coating dissolved or disappeared as soon as you began chewing.  This is because the candy coating was made of sugar, which easily dissolves in water (try adding a spoon full of table sugar to a glass of water and watch what happens), and the saliva in your mouth is mostly water.  Chemists would say that sugar is soluble in water.  Saliva and chewing are the first steps in digesting or breaking down your food into simpler components that your body can use for energy.

Your saliva does not dissolve the gum, however, because most modern chewing gums are made of a synthetic rubber (i.e. man-made, not natural), which is a type of oil-based polymer, such as  butadiene-styrene, vinyl acetate, or polyethylene (the same material in plastic grocery bags).  You may have already learned that oil (as well as oil-based substances) and water don't mix- they are not alike.  But chocolate does contain oil-based fatty substances, so the chocolate dissolves the gum.  Like dissolves like.  After adding the first piece of chocolate and chewing you should have noticed that the gum was much softer and stickier, and maybe much smaller than it was after you first chewed the gum alone.  If you add enough chocolate to the gum in your mouth (you may need 3 or 4 pieces) and continue chewing you should be able to make the gum disappear completely! 
variations and related activities
If you're not allergic to peanuts, try chewing a spoon full of peanut butter with your gum instead of chocolate.  Does the peanut butter also make the gum disappear?  Why do you think that is?

Instead of doing the entire experiment in your mouth, just chew the gum for a minute or two in your mouth, then put it in a cup or small bowl instead.  Add a couple spoonfuls of vegetable oil to the cup and use a spoon to stir and grind the gum.  Does it dissolve?  If not, add a little more vegetable oil.  Try repeating ths experiment with some other liquids.  Is gum more or less soluble in other liquids?

Solubility has it's limits, however, and you can easily test this.   Add one or two spoonfuls of sugar to a glass of water and observe what happens.  Does all of the sugar dissolve immediately?  Observe for a minute or two, has more dissolved?  Use a spoon tp stir the water and sugar.  Does it dissolve more easily?  Try adding more spoonfuls of sugar and stirring.  Does the sugar continue to dissolve?  Keep adding sugar until it will no longer dissolve in the water.  Now you have reached the solubility limit- the water simply can't hold any more sugar and we say it is saturated.  What would happen if you added more water to the glass?  Solubility also depends temperature.  With the help of an adult try repeating this experiment with warm or hot water.  Is sugar more soluble in hot water, i.e. can you make more spoonfuls of sugar dissolve?

Coming soon:

make rock candy
float letters off M&M's
pop rocks
dancing raisins
carbonated soft drinks
Lava Lamps
Dissolve egg shell in vinegar
Underwater fireworks (food coloring dissolves in water but not oil)
Oil-based and water-based paints
​
references and links to more information
Journal of Chemistry Education Classroom Activity #105. A Sticky Situation: Chewing Gum and Solubility 
  • https://pubs.acs.org/doi/pdf/10.1021/ed800135j
​
Learn more about solubility:
  • https://en.wikipedia.org/wiki/Solubility


Coming soon:

Saliva
​Digestion
​Solubility experiments


​Subject Tags
​
  • Food Chemistry
  • Kitchen Science
  • Oils
  • Polymers
  • ​Water

All Chemistry Subject Tags

All
Acid/Base Chemistry
Bubbles
Crystals
Density
Food Chemistry
Heat/Cold
Kitchen Science
Milk Chemistry
Oils
Phase/State Changes
Polymers
Soap
Water

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1 Comment

There's Metal in My Cereal!

3/22/2021

5 Comments

 


​Metals like iron and steel are used to make cars and ships and nails.  You may have also heard that you need iron-rich foods in your diet for good health; iron deficiency can lead to diseases like anemia.  But maybe you never realized that it's actually the same iron in each case.  That's right- you're eating exactly the same stuff found in nails every day, and in this experiment you will see it for yourself!



Este experimento está disponible en español
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Click and expand the tabs below to get started.
What you'll need
  • ​Small cups or bowls with tight-fitting lids (if you don't have cups with lids you can use any cup and just stir instead of shaking)
  • Zip-Lock or other small plastic bag
  • Plastic spoon or popsicle stick for stirring
  • Small neodymium (rare Earth) magnet(s), about the size and shape of a coin works best.  You should be able to find them in a hardware or department store.  An ordinary magnet will not work.  Some online suppliers.  [Note: neodymium magnets are very strong, so be careful to keep them away from any other magnets or metals, as they may pinch your fingers or skin.  They can also break easily producing sharp edges.]
  • Tape
  • Breakfast cereals (a nutritious or "healthy" brand like "Total" is best to start with, but you may want to try several different ones; look for cereals that list "Reduced Iron" or simply "Iron" in the ingredients, avoid those that list "Ferric Orthophosphate")
  • Water
  • Magnifying glass (optional)
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experimental procedure

  1. Tape your magnet to the bottom of your cup (on the outside).
  2. Add a few spoonfuls of dry cereal to your Zip-Lock bag, gently squeeze out most of the air and zip shut, then crush or smash the cereal into powder.
  3. Open the bag and fill your small cup mostly full with the crushed cereal.
  4. Add some water to the cereal in the cup and stir.  Add enough water to make a soupy mix, then attach the lid.  Make sure it's sealed tightly.
  5. Shake and mix the cereal in the cup for several minutes, holding the lid if necessary to make sure it doesn't come off.   If you don't have cups with lids you can use any cup and just stir instead of shaking.
  6. Carefully remove the lid and pour the cereal into another cup or bowl (don't throw it away yet, you may want to reuse it).
  7. Gently rinse the cup with water then look for tiny black particles or shavings that are stuck to the bottom of the cup near the magnet.  If you have a magnifying glass you can look very closely.  If you don't see any black particles try pouring the cereal mix back into the cup and shaking it for a few more minutes, then check again.  
  8. If you have another magnet and cup, repeat steps 1-7 with a different cereal to compare the amount of black shavings from each (be sure you use the same amount of cereal and shake the cup for the same amount of time).  If you only have one magnet or cup you can carefully remove the magnet without spilling the shavings, then pour them into another cup on onto a piece of paper and set aside (if you can dry them you might try sticking them onto another piece of tape).  Rinse you cup and then repeat steps 1-7.
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what's happening
Iron is a crucial component of a balanced diet (there should actually be enough iron in your body to make one or two small nails), but some people might not consume enough iron naturally to sustain themselves.  Because of this, many food manufacturers add iron to some foods to boost the average daily intake of this important mineral.  Some  foods may use a chemical form like ferric orthophosphate (FePO4) or ferrous sulfate (FeSO4), but most cereals simply use elemental (i.e. the pure atom) iron (Fe), also called "Reduced Iron".  

The iron you see in your cereal is elemental iron- actual metallic iron filings or shavings similar to the little flakes you might see come off of a steel wool pad when you squeeze or rub it, just much smaller.  That's right, you're eating metal in the morning!  But not to worry, acids in your digestive tract can change this metallic iron into a form that is easily absorbed and used by your body.  [Note: if you don't see any iron particles in this experiment you probably have a cereal that add one of the chemical forms listed above, so try a different cereal instead.]

These very tiny metal particles are mixed into the rest of the cereal ingredients, which is why you don't normally see them, but a magnet will attract these small iron filings that are present in the cereal, separating them from the other cereal components which are not attracted to the magnet (there's more information about magnetism in the reference links below).  Crushing the cereal and mixing it with water makes it much easier to separate the iron.  By the way, this is also why you need to use a wooden popsicle stick or plastic spoon to stir in Step 8 of the procedure above (if your cup doesn't have a lid).  Most metal spoons are made of steel, which contains a lot of iron and therefore will also be attracted to your magnet (although some types of steel are actually not very magnetic at all).

​Separating iron from cereal requires a powerful magnetic field, which is why we need to use a strong neodymium magnet, which is actually made from the elements neodymium, iron and boron (Nd2Fe14B).  Neodymium is rarely found in nature, so these magnets are sometimes called Rare Earth magnets.  Neodymium magnets are usually plated with a thin layer of another metal like nickel so they look like they're metal, but they are actually a type of ceramic.  Ceramic materials are similar to glass, so these magnets are fragile and can shatter or break quite easily, often producing sharp edges, if you allow them to slam together.  Because of this as well as their strength they must be handled very carefully.

Some breakfast cereals contain much more iron that other cereals.  You can find out how much iron any cereal contains by reading the "Nutrition Facts" labels on the side of the box (like the photo above).  For example, "Total" cereal contains 100% of the recommended daily iron allowance, while "Shredded Wheat" contains only 8% - this is why you should see more iron filings from the Total cereal.  Test several different cereals, does the amount of iron you see agree with the information on the labels?  Is it important that you use the same amount of each cereal and shake it for the same length of time?  Is it important to use the same amount of water?  Why or why not?
​
variations and related activities
After you have separated the iron from the cereal and water mix and rinsed the cup with water, carefully remove the magnet from the bottom of the cup.  Be sure not to tip the cup as once the magnet is removed the iron particles will be free to move.  Add a little bit of water to the cup and gently stir or swirl the cup to mix the iron particles.  Now hold the magnet near the sides or bottom of the cup and observe how the tiny iron particles move.  Try holding the magnet in different positions.  How does this affect the movement and orientation of the iron particles?  If you're careful you may be able to observe the shape of the magnetic field lines that surround the magnet.  You can also try this with a little bit of vegetable or baby oil instead of water in the cup [first tape the magnet to the bottom of the cup again to attract and pin all the iron, then carefully dump out the water and gently dry the cup without disturbing the iron particles, then add the oil].  How does the oil affect the motion of the iron particles?

If you hold your magnet near a flake of piece of the cereal, does it move?  What if you crush the cereal into smaller pieces?  Try floating a piece of cereal in a bowl of water, then holding the magnet very close.  Does it move now?

Another way to do this experiment is to place your magnet inside a small balloon, squeeze out any air inside, then tie it.  Now simply drop the balloon into your bowl of mashed cereal and water mixture, attach the lid and shake several minutes as before.  Open the lid, remove the balloon and rinse it with water to see the iron filings stuck to the balloon.

If you want to try another cool science experiment with your left over cereal (although it has nothing to do with iron or metal), check out the "Cheerios Effect" (see reference link below).  As the name suggests, it works best with Cheerios, but try it with other cereals too.
​
 
References and links to more information
Other variations of this experiment:
  • https://mocomi.com/iron-in-cereal/
  • https://www.scientificamerican.com/article/get-the-iron-out-of-your-breakfast-cereal-bring-science-home/
  • https://www.stevespanglerscience.com/lab/experiments/eating-nails-for-breakfast/
  • https://www.sciencebuddies.org/science-fair-projects/project-ideas/BioChem_p027/biotechnology-techniques/iron-in-breakfast-cereal
  • https://www.education.com/science-fair/article/iron-in-breakfast-cereal/​

Why iron is so important for your body:
  • https://www.cdc.gov/nutrition/InfantandToddlerNutrition/vitamins-minerals/iron.html
  • https://www.eatright.org/food/vitamins-and-supplements/types-of-vitamins-and-nutrients/iron
  • https://www.herzindagi.com/diet-nutrition/top-foods-high-iron-why-iron-is-important-for-body-article-158578
​
​Which breakfast cereals have the most iron:
  • https://foodwithiron.com/breakfast-cereals-high-in/
  • https://tools.myfooddata.com/nutrient-ranking-tool.php?nutrient=Iron&foodgroup=Breakfast-Cereals&sortby=Highest

Iron and magnetism (ferromagnetism):
  • https://sciencing.com/why-does-magnet-attract-iron-4572511.html
  • https://en.wikipedia.org/wiki/Ferromagnetism
  • https://www.thoughtco.com/not-all-iron-is-magnetic-3976017

Magnetic field lines:
  • https://www.thoughtco.com/magnetic-field-lines-4172630

The Cheerios Effect (and how it affects bugs that walk on water):
  • https://ed.ted.com/best_of_web/8HDeZKFr#watch
¡Hay metal en mi cereal!  (en español)
​Los metales como el hierro y el acero se utilizan para fabricar automóviles, barcos y clavos. Es posible que también haya escuchado que necesita alimentos ricos en hierro en su dieta para una buena salud; la deficiencia de hierro puede provocar enfermedades como la anemia. Pero tal vez nunca se dio cuenta de que en realidad es el mismo hierro en cada caso. Así es, estás comiendo exactamente lo mismo que se encuentra en las uñas todos los días, ¡y en este experimento lo verás por ti mismo!
Lo que necesitarás
  • Tazas o tazones pequeños con tapas ajustadas
  • Zip-Lock u otra bolsa de plástico pequeña
  • Cuchara de plástico o palito de paleta para revolver
  • Los imanes pequeños de neodimio (tierras raras), del tamaño y la forma de una moneda, funcionan mejor. Debería poder encontrarlos en una ferretería o una tienda por departamentos. Un imán ordinario no funcionará. Algunos proveedores en línea. [Nota: los imanes de neodimio son muy fuertes, así que tenga cuidado de mantenerlos alejados de otros imanes o metales, ya que pueden pellizcarle los dedos o la piel. También pueden romperse fácilmente produciendo bordes afilados.]
  • Cinta
  • Cereales para el desayuno (una marca nutritiva o "saludable" como "Total" es mejor para empezar, pero es posible que desee probar varios diferentes; busque cereales que incluyan "Hierro reducido" en los ingredientes, evite los que indiquen "Férrico Ortofosfato ")
  • Agua
  • Lupa (opcional)
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Procedimiento experimental
  1. Pegue con cinta adhesiva su imán al fondo de su taza (en el exterior).
  2. Agregue algunas cucharadas de cereal seco a su bolsa Zip-Lock, exprima suavemente la mayor parte del aire y cierre la cremallera, luego triture o triture el cereal en polvo.
  3. Abra la bolsa y llene su taza pequeña casi completamente llena con el cereal triturado.
  4. Agregue un poco de agua al cereal en la taza y revuelva. Agregue suficiente agua para hacer una mezcla espesa, luego coloque la tapa. Asegúrate de que esté bien sellado.
  5. Agite y mezcle el cereal en la taza durante varios minutos, sosteniendo la tapa si es necesario para asegurarse de que no se desprenda.  Si no tiene una tapa para su taza, puede simplemente revolver la mezcla de cereal / agua con un palito de helado o una cuchara de plástico, pero probablemente tomará mucho más tiempo separar las virutas negras.
  6. Retire con cuidado la tapa y vierta el cereal en otra taza o tazón (no lo tire todavía, es posible que desee reutilizarlo).
  7. Enjuague suavemente la taza con agua y luego busque pequeñas partículas negras o virutas que estén pegadas al fondo de la taza cerca del imán. Si tiene una lupa, puede mirar muy de cerca. Si no ve ninguna partícula negra, intente verter la mezcla de cereal nuevamente en la taza y agitarla durante unos minutos más, luego vuelva a verificar.
  8. Si tiene otro imán y una taza, repita los pasos 1-7 con un cereal diferente para comparar la cantidad de virutas negras de cada uno (asegúrese de usar la misma cantidad de cereal y agite la taza durante la misma cantidad de tiempo). Si solo tiene un imán o una taza, puede quitar con cuidado el imán sin derramar las virutas, luego verterlas en otra taza sobre un pedazo de papel y dejar a un lado (si puede secarlas, puede intentar pegarlas en otro trozo de cinta adhesiva). ). Enjuague su taza y luego repita los pasos 1-7.
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QUÉ ESTA PASANDO
El hierro es un componente crucial de una dieta equilibrada (en realidad, debería haber suficiente hierro en su cuerpo para hacer una o dos uñas pequeñas), pero es posible que algunas personas no consuman suficiente hierro de forma natural para mantenerse. Debido a esto, muchos fabricantes de alimentos agregan hierro a algunos alimentos para aumentar la ingesta diaria promedio de este importante mineral. Algunos alimentos pueden usar una forma química como el ortofosfato férrico (FePO4) o el sulfato ferroso (FeSO4), pero la mayoría de los cereales simplemente usan hierro (Fe) elemental (es decir, el átomo puro), también llamado "Hierro reducido". 
 
El hierro que ve en su cereal es hierro elemental, limaduras o virutas de hierro metálico reales similares a las pequeñas escamas que puede ver salir de una almohadilla de lana de acero cuando la aprieta o frota, pero mucho más pequeñas. Así es, ¡estás comiendo metal por la mañana! Pero no se preocupe, los ácidos en su tracto digestivo pueden cambiar este hierro metálico a una forma que su cuerpo absorbe y utiliza fácilmente. [Nota: si no ve ninguna partícula de hierro en este experimento, probablemente tenga un cereal que agregue una de las formas químicas mencionadas anteriormente, así que pruebe con un cereal diferente en su lugar.] 
 
Estas diminutas partículas de metal se mezclan con el resto del ingredientes de los cereales, por lo que normalmente no los ve, pero un imán atraerá estas pequeñas limaduras de hierro que están presentes en el cereal, separándolos de los otros componentes del cereal que no son atraídos por el imán (hay más información sobre el magnetismo en los enlaces de referencia a continuación). Triturar el cereal y mezclarlo con agua hace que sea mucho más fácil separar el hierro. Por cierto, esta es también la razón por la que debe usar un palito de paleta de madera o una cuchara de plástico para revolver en el Paso 8 del procedimiento anterior (si su taza no tiene tapa). La mayoría de las cucharas de metal están hechas de acero, que contiene mucho hierro y, por lo tanto, también se sentirán atraídas por su imán (aunque algunos tipos de acero en realidad no son muy magnéticos).

​La separación del hierro del cereal requiere un campo magnético potente, por lo que necesitamos utilizar un imán de neodimio potente, que en realidad está hecho de los elementos neodimio, hierro y boro (Nd2Fe14B). El neodimio rara vez se encuentra en la naturaleza, por lo que estos imanes a veces se denominan imanes de tierras raras. Los imanes de neodimio generalmente se recubren con una capa delgada de otro metal como el níquel para que parezcan de metal, pero en realidad son un tipo de cerámica. Los materiales cerámicos son similares al vidrio, por lo que estos imanes son frágiles y pueden romperse o romperse con bastante facilidad, a menudo produciendo bordes afilados, si permite que se golpeen entre sí. Debido a esto, así como a su fuerza, deben manejarse con mucho cuidado. 
 
Algunos cereales para el desayuno contienen mucho más hierro que otros cereales. Puede averiguar cuánto hierro contiene cualquier cereal leyendo las etiquetas de "Información nutricional" al costado de la caja (como la foto de arriba). Por ejemplo, el cereal "Total" contiene el 100% de la cantidad diaria recomendada de hierro, mientras que el "Trigo desmenuzado" contiene solo el 8%; es por eso que debería ver más limaduras de hierro del cereal Total. Pruebe varios cereales diferentes, ¿la cantidad de hierro que ve coincide con la información de las etiquetas? ¿Es importante que use la misma cantidad de cada cereal y lo agite durante el mismo tiempo? ¿Es importante utilizar la misma cantidad de agua? ¿Por qué o por qué no?
variaciones y actividades relacionada
Próximamente
REFERENCIAS Y ENLACES A MÁS INFORMACIÓN
Otras variaciones de este experimento:
  • https://mocomi.com/iron-in-cereal/
  • https://www.scientificamerican.com/article/get-the-iron-out-of-your-breakfast-cereal-bring-science-home/
  • https://www.stevespanglerscience.com/lab/experiments/eating-nails-for-breakfast/
  • https://www.sciencebuddies.org/science-fair-projects/project-ideas/BioChem_p027/biotechnology-techniques/iron-in-breakfast-cereal
  • https://www.education.com/science-fair/article/iron-in-breakfast-cereal/​

Por qué el hierro es tan importante para tu cuerpo:
  • https://www.cdc.gov/nutrition/InfantandToddlerNutrition/vitamins-minerals/iron.html
  • https://www.eatright.org/food/vitamins-and-supplements/types-of-vitamins-and-nutrients/iron
  • https://www.herzindagi.com/diet-nutrition/top-foods-high-iron-why-iron-is-important-for-body-article-158578
​
​Qué cereales para el desayuno tienen más hierro:
  • https://foodwithiron.com/breakfast-cereals-high-in/
  • https://tools.myfooddata.com/nutrient-ranking-tool.php?nutrient=Iron&foodgroup=Breakfast-Cereals&sortby=Highest

Hierro y magnetismo (ferromagnetismo):
  • https://sciencing.com/why-does-magnet-attract-iron-4572511.html
  • https://en.wikipedia.org/wiki/Ferromagnetism
  • https://www.thoughtco.com/not-all-iron-is-magnetic-3976017

Líneas de campo magnético:
  • https://www.thoughtco.com/magnetic-field-lines-4172630

El efecto Cheerios (y cómo afecta a los insectos que caminan sobre el agua):
  • https://ed.ted.com/best_of_web/8HDeZKFr#watch

Subject Tags

  • Food Chemistry
  • Kitchen Science

All Chemistry Subject Tags

All
Acid/Base Chemistry
Bubbles
Crystals
Density
Food Chemistry
Heat/Cold
Kitchen Science
Milk Chemistry
Oils
Phase/State Changes
Polymers
Soap
Water

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5 Comments

Baking with Gas

3/22/2021

0 Comments

 
Have you ever wondered what makes a flour dough rise, or why there are lots of little holes inside your bread or pancakes?  And what is the difference between baking soda and baking powder?  Well, you're in luck because that's what this experiment is all about.

Este experimento está disponible en español

Click and expand the tabs below to get started.​
what you'll need
  • All-purpose flour
  • Baking powder
  • Baking soda
  • Water (room temperature)
  • Vinegar or lemon juice
  • 3 small cups (plastic is fine).
  • Teaspoon​ for measuring
  • Small spoons or popsicle sticks for stirring
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experimental procedure
  1. Place about 1 teaspoon of baking powder in one of your small cups.  
  2. Place about 1 teaspoon of baking soda in another small cup.
  3. Place about 1 teaspoon of water into each of the cups from Steps 1 and 2 and stir each with a clean spoon or popsicle stick.
  4. Observe closely what is happening in each of the cups.  Do you see any bubbles?  Do you hear anything?
  5. Add about 1 teaspoon of vinegar or lemon juice to the baking soda cup.  Do you observe anything happening now?
  6. Place about 1 teaspoon of flour in a third clean cup.  Add about 1 teaspoon of baking powder and mix thoroughly with a clean spoon or popsicle stick.
  7. Add about 2 teaspoons of water to the flour and baking powder in the third cup and stir.  
  8. Observe closely what is happening.
what's happening
Baking soda is the common name for sodium bicarbonate, a type of substance or chemical called a base.  When it is mixed with water is simply dissolves with no reaction.  Baking powder, however, contains not only sodium bicarbonate but also another type of chemical called an acid (or sometimes two different acids).  When these chemicals dissolve in water the base sodium bicarbonate reacts with the acid.  This is called a chemical reaction because it results in the creation of one of more new and completely different substances.  Acids and bases often react with each other.  In this reaction the new substance is a gas called carbon dioxide, which is the tiny bubbles that you observe.  You can also hear them popping as the gas escapes.  

The baking soda did not react because there was no acid present, but if you add a little acid like vinegar or lemon juice then you will get a reaction that also produces carbon dioxide gas- in fact, lots of gas bubbles and foam!  You may have done this reaction before to make the famous vinegar and baking soda volcano!

Chemical reactions like this are used in baking breads, pancakes, cookies and other foods.  When mixed with flour and water to make a dough the gas bubbles are trapped inside and cause the dough to inflate like a balloon or rise.  That's what happened in the third cup when you added flour.  ​This is called leavening, and ingredients like baking powder or baking soda are call leavening agents.  Baking this dough at high temperature in an oven causes the flour molecules to lock together into a firm solid structure giving us something good to eat!  Meanwhile the carbon dioxide bubbles eventually pop and the gas escapes, leaving behind the tiny little holes we see in baked goods.
​
variations and related activities
Some recipes use baking soda instead of baking powder because there is some other ingredient already present that provides the acid needed to produce the gas.  Some recipes even use both baking soda and baking powder to produce carbon dioxide at different times during the baking.  

Most baking powder used today is "Double Acting Baking Powder".  It contains two different acids, one which reacts as soon as the water is added and a second acid that doesn't react until it reaches a certain high temperature.  This causes the dough to rise twice- once when it is first mixed then again during baking in the oven.

You can continue this activity in a tasty way with a simple homemade pancake recipe (see link below), and make it into a real experiment by making some pancakes without the baking powder and baking soda.  How do these pancakes compare to the normal ones?  What if you leave out one of the other ingredients? 

Pizza dough and some other baked goods use a very different ingredient- yeast- to make the dough rise.  Yeasts are actually tiny living organisms called fungi that "eat" sugars and "burp" carbon dioxide gas.  Check out the references below if you would like to experiment with yeast.
 
references and links to more information
What purpose do the various ingredients serve in baking?:
  • https://kidpillar.com/science-of-baking-for-kids/
  • https://washingtonparent.com/teach-kids-science-through-baking/
  • http://www.bakingscience.com

Try a pancake science recipe and experiment:
  • https://science-u.org/experiments/pancake-science.html

Other baking science experiments:
  • https://www.sciencebuddies.org/science-fair-projects/project-ideas/experiment-with-baking

More baking Soda experiments:
  • https://babbledabbledo.com/5-easy-baking-soda-science-projects-your-kids-will-love/
  • https://www.steampoweredfamily.com/activities/baking-soda-and-vinegar-experiments/

Yeast science and baking experiments:
  • https://kidsdiscover.com/teacherresources/science-of-yeast-for-kids/
  • https://www.education.com/science-fair/article/biology_foamy/
  • https://www.nationalgeographic.com/history/article/funky-science-yeast-gassy-microbe-behind-coronavirus-pandemic-bread
​
Hornear con gas (en español)
​¿Alguna vez te has preguntado qué hace que la masa de harina se eleve o por qué hay muchos pequeños agujeros dentro de tu pan o panqueques? ¿Y cuál es la diferencia entre bicarbonato de sodio y levadura en polvo? Bueno, estás de suerte porque de eso se trata este experimento.
Lo que necesitarás
  • Harina para todo uso
  • Levadura en polvo
  • Bicarbonato de sodio
  • Agua (temperatura ambiente)
  • Vinagre o jugo de limón
  • 3 tazas pequeñas (de plástico está bien).
  • Cucharadita para medir
Cucharas pequeñas o palitos de helado para revolver
Picture
Picture
Picture
Picture
Procedimiento experimental
  1. Coloque aproximadamente 1 cucharadita de polvo de hornear en una de sus tazas pequeñas.
  2. Coloque aproximadamente 1 cucharadita de bicarbonato de sodio en otra taza pequeña.
  3. Coloque aproximadamente 1 cucharadita de agua en cada una de las tazas de los Pasos 1 y 2 y revuelva cada una con una cuchara limpia o un palito de paleta.
  4. Observa de cerca lo que sucede en cada uno de los vasos. ¿Ves burbujas? ¿Escuchas algo?
  5. Agregue aproximadamente 1 cucharadita de vinagre o jugo de limón a la taza de bicarbonato de sodio. ¿Observa algo que está sucediendo ahora?
  6. Coloque aproximadamente 1 cucharadita de harina en una tercera taza limpia. Agregue aproximadamente 1 cucharadita de polvo de hornear y mezcle bien con una cuchara limpia o un palito de paleta.
  7. Agregue aproximadamente 2 cucharaditas de agua a la harina y el polvo de hornear en la tercera taza y revuelva.
  8. Observe de cerca lo que está sucediendo.
Qué esta pasando
Bicarbonato de sodio es el nombre común del bicarbonato de sodio, un tipo de sustancia o químico llamado base. Cuando se mezcla con agua, simplemente se disuelve sin reacción. Sin embargo, el polvo de hornear contiene no solo bicarbonato de sodio, sino también otro tipo de químico llamado ácido (oa veces dos ácidos diferentes). Cuando estos productos químicos se disuelven en agua, el bicarbonato de sodio básico reacciona con el ácido. Esto se llama reacción química porque da como resultado la creación de una o más sustancias nuevas y completamente diferentes. Los ácidos y las bases a menudo reaccionan entre sí. En esta reacción, la nueva sustancia es un gas llamado dióxido de carbono, que son las diminutas burbujas que observas. También puede escucharlos estallar cuando el gas se escapa. 
 
El bicarbonato de sodio no reaccionó porque no había ácido presente, pero si agrega un poco de ácido como vinagre o jugo de limón, obtendrá una reacción que también produce dióxido de carbono, de hecho, ¡muchas burbujas de gas y espuma! ¡Es posible que hayas hecho esta reacción antes para hacer el famoso volcán de vinagre y bicarbonato de sodio! 
 
Las reacciones químicas como esta se utilizan para hornear panes, panqueques, galletas y otros alimentos. Cuando se mezcla con harina y agua para hacer una masa, las burbujas de gas quedan atrapadas en el interior y hacen que la masa se infle como un globo o se eleve. Eso es lo que sucedió en la tercera taza cuando agregaste harina. ¡Hornear esta masa a alta temperatura en un horno hace que las moléculas de harina se bloqueen en una estructura sólida y firme que nos da algo bueno para comer! Mientras tanto, las burbujas de dióxido de carbono eventualmente explotan y el gas escapa, dejando atrás los pequeños agujeros que vemos en los productos horneados.
Variaciones y actividades relacionadas
Algunas recetas usan bicarbonato de sodio en lugar de polvo de hornear porque ya hay algún otro ingrediente presente que proporciona el ácido necesario para producir el gas. Algunas recetas incluso usan bicarbonato de sodio y polvo de hornear para producir dióxido de carbono en diferentes momentos durante la cocción. 
 
La mayor parte del polvo de hornear que se usa hoy en día es el "polvo de hornear de doble acción". Contiene dos ácidos diferentes, uno que reacciona tan pronto como se agrega el agua y un segundo ácido que no reacciona hasta que alcanza una cierta temperatura alta. Esto hace que la masa suba dos veces, una cuando se mezcla por primera vez y luego nuevamente durante la cocción en el horno. 
 
Puede continuar este experimento de una manera sabrosa con una receta de panqueques casera simple (link abajo).

La masa de pizza y algunos otros productos horneados utilizan un ingrediente muy diferente, la levadura, para hacer que la masa suba. Las levaduras son en realidad pequeños organismos vivos llamados hongos que "comen" azúcares y "eructan" gas de dióxido de carbono. Consulte las referencias a continuación si desea experimentar con levadura

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  • Food Chemistry
  • Kitchen Science​




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Baking Crackers

8/17/2020

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Think about a nice, creamy pat of butter, sitting on a freshly baked, homemade cracker!  Is your mouth watering yet?  There is a surprising amount of science to be found in the kitchen, so let’s take a look and see what we can learn!

​You can also make your own butter to put on your crackers!

Picture
what you'll need
  • 1 1/2 cups all-purpose flour
  • 4 tablespoons butter
  • 1/4 cup water
  • 1 tablespoon honey
  • Mixing bowl
  • Measuring cups and spoons
  • Butter knife and spoon
  • Cookie or baking sheet
  • Rolling pin (optional)
  • Oven and Hot pads
experimental procedure
  1. Preheat the oven to 400 degrees Fahrenheit.  Then,
  2. Put 1 1/4 cups of flour in the big bowl.  Be sure to fill the cup up to the proper mark, and then level it off, because if we use too much flour, the dough will not stick together.
  3. Cut up the butter into little pieces, and drop it in the flour.
  4. Use your hands to squish the flour and the butter together, until the mixture is crumbly.  The smaller the chunks of butter are, the better the crackers will be.
  5. Add the water and the honey.  Squish the mixture around again.  You want to end up with a squishy, sticky ball of dough with very few (if any) recognizable lumps of butter in it.
  6. Dust your cookie sheet with a little bit of flour (less than ¼ cup).  Also, put some flour on your hands, and rub your hands over the rolling pin, if you are using one.
  7. Put the dough on the cookie sheet and smush it down flat with your hands.  If you are using a rolling pin, use it to roll out the dough so it is very flat.  When you smush the dough straight down with your hands, you should barely feel it move.
  8. Cut the dough into shapes (squares, rectangles, triangles, etc.) with the butter knife.
  9. Have a grown up put the cookie sheet in the oven, and set the timer for ten minutes.
  10. After 10 minutes, have a grown up take the cookie sheet out of the oven, and let the crackers cool.  They will not be very crispy at first, but they will get a little more crispy as they cool and dry.​

what's happening
Let’s take a closer look at our crackers.  Do they look poofy at all to you?  Or are they pretty flat?  They should be flat, because we didn’t add any leavening to them.  Leavening is the cooking term for any ingredient that will make things that you bake poofy.  Things like baking powder and baking soda make bread and cakes rise because they react with other ingredients in the dough to make carbon dioxide bubbles.  The holes that we see when we look at a piece of bread are the outsides of those carbon dioxide bubbles.  The carbon dioxide escapes into the air, and we have a delicious piece of bread.  However, in this case, we didn’t want the crackers to be poofy, so we didn’t put anything in that would make the bubbles.  So, our crackers should be flat and delicious!
​

variations and related activities
Coming soon.
references and links to more information
Coming soon.

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  • Kitchen Science​

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I Can't Believe It IS Butter!

8/17/2020

1 Comment

 
Picture

​
You won't believe how easy it is to make your own butter simply by shaking a cup of heavy whipping cream, which comes from milk.  Give it a try- and you even get to eat this experiment when you're done!

Click tabs below to get started
what you'll need
  • Heavy Whipping Cream
  • Small jar or plastic container with a tight fitting lid
  • Table salt
  • Cold water
  • Knife or popsicle stick
  • Some bread or crackers if you want to eat your butter

​For whipped cream (optional):
  • Mixing bowl
  • Wire whisk or electric mixer
  • Powdered sugar

Be sure to ask your mom, dad or another adult to help-you can share your butter with them.
experimental procedure
  1. Pour some heavy whipping cream into a small jar or plastic container.  For just yourself one or two tablespoons of cream is fine, so be sure to use a very small jar.  If your jar is a larger you can use more, but either way, fill the jar only about half full so you have plenty of room. 
  2. Make sure the lid is closed tightly, then shake the jar vigorously.  Use slow, deliberate strokes, almost like you are trying to throw the jar as hard as you can but then stopping your arm suddenly (don't let go!)  The harder you shake, the quicker you will make your butter. 
  3. At first you should hear (and feel) the cream sloshing back and forth with each stroke, but after a minute or two you won't hear or feel anything moving inside.  If you like, carefully open the lid a little and peek inside. You should see a thick, creamy white foam.  This is whipped cream- taste a little with your fingertip if you like (of course there is no sugar, so it won't be sweet). 
  4. Carefully replace the lid, making sure it is very tight and won't leak, and continue shaking as before.  It feels like nothing is happening, but stick with it.
  5. After a few more minutes you will finally hear a liquid begin to slosh around again, and this time you should also feel a thud as something solid slams against the jar.  Shake it a few more times very hard.
  6. Carefully open the lid and look inside.  You should see a clump or perhaps a ball of solid butter as well as a thin milky liquid. The butter may be white or yellow.  The liquid is buttermilk. Taste a little of the buttermilk if you like.
  7. Carefully pour off all of the buttermilk into another jar or cup if you want to save it for cooking or baking (buttermilk pancakes or biscuits), otherwise just pour it down the sink.  Use your lid as you pour to make sure you don't lose the butter you've worked so hard to make.
  8. Add cold water to the jar of butter (about 3/4 full), tightly close the lid and shake it vigorously for about a minute to rinse your butter.  This time you don't need to shake slow and hard, normal shaking is fine. 
  9. Carefully open the lid and pour off all the water as before.  Add more cold water and repeat one or two more times until the rinse water is clear.  If you like, you can also use your knife or popsicle stick to stir and knead the butter to rinse it even more thoroughly.

Once you finish rinsing your butter, remove all the water and taste it on some bread or a cracker.  Most butter you find in the grocery store has salt added, but your butter is unsalted (sometimes called sweet butter).  If you don't like the taste, add a pinch of salt.
​
​
Additional Optional Experimental Procedure:

You can also make your own real whipped cream.

  1. Chill your of heavy whipping cream in the refrigerator (or even the freezer for an hour or so) so that it is very cold. 
  2. Pour one or two cups of chilled cream into a small mixing bowl.
  3. Add about 1/4 cup of powdered sugar per cup of cream.  You may also want to add a little vanilla extract or lemon juice for flavor.
  4. Use a wire whisk or electric mixer to whip the cream very quickly for a minute or two or until nice and fluffy.  Don't over-whip it or you will get butter again!
  5. Taste your whipped cream!​​
what's happening
Butter is very interesting scientifically.  We  used cream to make butter, but where does cream come from?  Cream comes from cows.  It is part of the milk that a cow gives.  It has a lot of fat in it.  Fat occurs in pieces called molecules.  These molecules like to stick together in big clumps, but at the dairy they homogenized the milk to keep the fat and everything else all mixed up well.  When you shake the cream, however, the molecules which were floating around start sticking to each other.  When enough of them stick together they won't float or stay mixed up any more and you have butter!

​
more detailed explanation
Picture
You've probably heard that oil and water don't mix, but milk is in fact a mixture of many different components, including sugars, proteins, fats and yes, water.  [Fats and oils are basically similar molecules, also often called lipids, and made of smaller building blocks called fatty acids.  Although fat, oil and lipid are often used to refer to fats, "oil" generally refers to a fat that is liquid at normal room temperature and "fat" is solid at room temperature.]  The oil or fat in milk can mix with water without separating because they form into little globules sort of like water balloons.  The fat is inside a thin skin or membrane which helps attract water somewhat, and because fat is less dense than water, the globules float and form what's called a colloidal suspension or emulsion.  The smaller the globules, the easier it is for them to remain emulsified, but if they are too large they will separate and float to the surface.  Years ago before milk was homogenized, the fat globules would float to the top and form a layer called the cream, which contained most of the milk's fat.  Homogenization breaks up the larger globules into smaller ones, which, along with the milk proteins that then help form a stronger globule membrane, prevent this separation.  The cream you buy at the grocery store is separated at the dairy and then homogenized to keep the fat suspended in the liquid.  Heavy whipping cream means that it has a very high fat content, 36-40% (normal cream is about 30% fat, while Half & Half is 12% and whole milk 3.5% fat).  Butter is essentially pure milk fat.

In our heavy cream, the fat globules are still emulsified, or suspended in the water along with some protein and sugar.  If we shake the cream though, the globules will begin to crash into one another and pop or burst their membranes.  When this happens the fat molecules spill out and clump together with other fat molecules.  At first as this happens the fat traps a lot of air and forms bubbles or foam, which is the whipped cream.  The more you shake it, however, the more bubbles pop and the more densely the fat clumps become until they can no longer remain suspended in the water, and they separate completely.  This is the butter, and the remaining liquid, mostly water and proteins, is called buttermilk. 
​
The butter you make is not only good to eat, but will stay fresh for a long time, especially if it is thoroughly rinsed of all the milk liquid, since the milk can spoil.  Adding sugar to the whipped cream not only sweetens and thickens it, but helps prevent the fat bubbles from popping so that it will stay a light fluffy foam much longer.

variations and related activities
Try using cold heavy whipping cream to make butter.  Try warm cream.  Does it take more or less shaking to get to butter?  How do you think temperature affects this process?  If you like these milk science activities, you can also try our Milk Fireworks experiment, as well as making cottage cheese and glue (see link below) from milk.
references and links to more information
Others versions of this activity:
  • https://www.sfi.ie/site-files/primary-science/media/pdfs/col/sci_at_home_make_butter.pdf
  • http://www.sciencebuddies.org/science-fair-projects/project_ideas/FoodSci_p050.shtml#summary
  • http://foodformyfamily.com/recipes/food-science-camp-how-to-make-butter
  • http://www.makeandtakes.com/edible-science-experiment-making-butter-whipped-cream
  • http://www.scientificamerican.com/article/bring-science-home-butter-emulsion/

Experiment with the temperature of the cream:
  • http://www.scientificamerican.com/article/bring-science-home-shaking-butter/

Learn more about milk chemistry:
  • https://www.uoguelph.ca/foodscience/book-page/milk-structure

What is homogenized milk?:
  • milklife.com/articles/nutrition/what-homogenized-milk

Whipped cream as a science fair project:
  • https://www.sciencebuddies.org/science-fair-projects/project-ideas/FoodSci_p022/cooking-food-science/fresh-whipped-cream-that-lasts#summary
  • http://observationalgastrophysics.blogspot.com/2010/03/by-naveen-whipped-cream-has-been-on-my.html

What happens when whipped cream comes out of a can?:
  • https://science.nasa.gov/science-news/science-at-nasa/2008/25apr_cvx2/​

You can also make glue from milk:
  • http://www.science-sparks.com/2012/02/06/make-glue-from-milk/

​

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  • Kitchen Science
  • ​Milk Chemistry

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1 Comment

Baby Diaper Dissection

8/8/2020

4 Comments

 

Have you ever wondered what's really inside a baby diaper?  No, not what you're probably thinking, but rather what's inside the diaper material itself.  If you think it's just some cotton fluff you're in for a big surprise!
Picture
Click and expand the tabs below to get started.
What you'll need

  • 2 or 3 disposable baby diapers
  • Cotton diaper or towel
  • Sponge
  • Paper plates, newspaper or a small grocery or garbage bag
  • 2 small cups
  • Scissors
  • Water
​
Picture
experimental procedure
  1. Open a Pampers or other brand of disposable diaper and inspect.  Compare to a cloth diaper or towel and a sponge.
  2. Place the diapers and sponge on paper plates, newspaper or a plastic bag spread out like a table cloth.  Add some water to each.  How much can each one absorb?
  3. To understand why the disposable diaper can hold so much more water, place a new dry disposable diaper on a paper plate, newspaper or garbage bag (some people like to do this step with the diaper inside the garbage bag).  Using scissors, carefully cut through the cloth-like inside layer and peel it open to reveal the cottony fibers inside.
  4. Squeeze and rub the cotton with your fingers.  You should feel some powder between the fibers.
  5. Separate the white powder from the cotton fibers by rubbing and peeling.  Collect as much as you can and place it into a small cup.
  6. Add water to the powder in the cup, a little at a time and observe what happens.  Keep adding water until no more can be absorbed.  Are you amazed at how much water it absorbs without dripping?
​
what's happening
Modern disposable baby diapers contain a small amount (4-5 grams) of polyacrylic acid in a powder form (sodium polyacrylate), which is mixed into the fluff in the middle layer of the diaper.  The inside layer of the diaper allows water to pass through it into the absorbent middle layer, and the outer layer is waterproof, so both baby and mommy stay dry.  Polyacrylic acid can absorb about more than 100 times its own weight in water, which is why an average sized diaper can absorb up to 16 ounces of water.  Luckily that's more than a baby usually pees. 

Picture
Why is this powder so good at absorbing water?   Polyacrylic acid is a polymer made from the monomer acrylic acid.  Polymer molecules are kind of like long chain made up of lots of identical links (the monomers).  Polyacrylic acid chains contain thousands of monomer units, as well as cross-linking between different molecule chains, which makes them kind of tangle together.  Most polymers, such as polyethylene and polystyrene (used in trash bags, plastic bottles, and Styrofoam®, for example) are hydrophobic, meaning they repel water.  Polyacrylic acid, however, is very hydrophilic - it attracts water- because of the carboxylic acid groups (COOH) in the polymer, which can hydrogen-bond to water molecules.  The cross-linking also helps trap lots of bonded water molecules inside the tangled chains.

Variations and related activities
You can make this activity more colorful by adding a few drops of food coloring to the water.  Also try adding some table salt to the water.  What happens?  [Table salt is sodium chloride (NaCl) and the chloride ions will bond with the SAP and prevent water molecules from doing so.]

If you place the wet polymer on a towel or napkin and allow it to dry out for a few days it will dehydrate and shrink back to almost its original powder form and can be used over an over again.

Polyacrylic acid, often just called baby diaper polymer or super absorbent polymer (SAP), comes in many forms and has many other applications.  SAP is often used to clean up hazardous waste spills- even more hazardous than what ends up in a baby diaper!  Just sprinkle the dry powder on the spilled liquid and then sweep or vacuum it up.  You can also find SAP in moisture-control potting soils at a garden store.  If you over-water your plants the SAP will absorb the excess water.  As the soil dries the SAP dehydrates and the excess water returns to the soil, maintaining just the right amount or moisture for the plant to thrive.  You can also buy headbands and neckbands that contain SAP inside, after you wet them the water evaporates slowly and keeps you cool for a long time (see the reference link below to make your own!)

You can buy Instant Snow powder from many stores online (see references below). Instant snow is exactly the same material, it's just ground up into a much finer powder. This causes it to form smaller molecular structures and puff up instantly when it absorbs water, giving it the look and feel of real snow.  It's often used in movies when they want snow in a scene without the need for cold temperatures- and the wet mess when it melts!

Orbeez and other water beads are clear spheres and other fun shapes made from the same polyacrylic acid SAP material, but prepared a little differently to form the shapes you see when they absorb water.  Typical Orbeez spheres start as 3 or 4 mm beads, but can grow to more than 1" in diameter as they absorb water. Because they are composed almost entirely of water when fully grown, they are essentially invisible in a bowl of water (as long as both the spheres and the liquid water are clean).  Water is water.  The index of refraction (a measure of how light bends as it passes through a material) of the liquid water is the same as the water in the sphere, so light rays are not refracted as they pass from the water in the bowl to the water in the beads, and the spheres are therefore almost completely indistinguishable from the rest of the water.  They also bounce (but can break if you bounce them too hard) and act as little magnifying glasses.  Just as with the baby diaper polymer, you can add food colors to make colored Orbeez, and if you let them dry they will shrink back down to little beads that you can use over and over again.

references and links to more information
The science of sodium polyacrylate and SAP's:
  • https://en.wikipedia.org/wiki/Sodium_polyacrylate
  • https://m2polymer.com/cross-linked-sodium-polyacrylate

Here are some other ways to do this experiment:
  • https://www.stevespanglerscience.com/lab/experiments/baby-diaper-secret-vanishing-water/
  • https://www.scientificamerican.com/article/diapers-what-keeps-babies-and-astronauts-from-springing-a-leak/

This video from Science Beyond at the St. Louis Science Center shows you the secret behind one of our most popular demonstrations:
  • https://www.youtube.com/watch?v=8giiZjOOwsU

Fun with Instant Snow powder:
  • https://www.stevespanglerscience.com/lab/experiments/insta-snow-ideas/

Orbeez!:
  • https://mayatoys.net/pages/orbeez

Make your own cooling headband or neck bandana with SAP:
  • https://www.ehow.com/how_5247874_make-icy-neck-wraps-headbands.html
  • https://www.instructables.com/id/Sew-Very-Useful-Neck-Cooler/


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4 Comments

Super Giant Soap Bubbles

7/28/2020

2 Comments

 
What's more fun than bubbles?  How about humongous bubbles!  Making super giant-sized soap bubbles is actually pretty easy, but it turns out there is a lot more science going on here than you probably thought.
Picture
from Soap Bubble Wiki (link below)
Click and expand the tabs below to get started
what you'll need
For Bubble Solution (1 gallon):
​
  • 10 tablespoons dish soap or detergent- Dawn seems to work best, try to get unscented or Professional (usually available at Sam's Club or Costco)
  • 1 teaspoon Guar Gum (available at most health food stores. If you can't find Guar Gum, cornstarch is a reasonable substitute.)
  • Baking powder (not baking soda)
  • 3 teaspoons Rubbing (Isopropyl) alcohol
  • Bucket or other container to hold about 1 gallon (a 5 gallon bucket is great if you want to make more)
  • Small cup
  • A small spoon or popsicle stick and a big spoon
  • Measuring spoons or cups
​
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For each giant bubble wand:
​
  • 2 garden stakes or sticks, ~12" - 24" long (something with a hole or loop in one end is best so that you can tie the cord to the stakes)
  • Cord or rope (soft braided cotton works best, not too thick ~1/8" to 1/4", ~8' long)
  • A fairly heavy hex nut or washer(s) (with a hole your cord will fit through)
  • Scissors

​For small bubble wands:
​
  • Drinking straws
  • Cotton yarn or string
​
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basic procedure
Prepare bubble solution (for 1 gallon)
​
  1. ​Measure 1 teaspoon of guar gum in a small cup or bowl.
  2. Slowly add 2-3 teaspoons of isopropyl (rubbing) alcohol while stirring to make a smooth slurry or paste.  Set aside. [If you're using cornstarch instead of guar gum you can use water instead of rubbing alcohol.]
  3. Add 1 - 2 quarts of very warm water to a bucket large enough to hold at least 1 gallon.
  4. While stirring the water with a large spoon, slowing add the guar gum and alcohol slurry.  Rinse the cup once or twice with water from the bucket to get all of the guar gum.
  5. Let the water stand for several minutes, stirring occasionally.  You may notice the solution thicken a bit as the guar gum hydrates (absorbs water).
  6. Add more water (cold is fine) to make a total of 1 gallon and stir.
  7. Add 2 teaspoons baking powder and stir until dissolved.
  8. Add 10 tablespoons dish soap (or 1/2 cup + 2 tablespoons), stirring gently.  Try not to make many bubbles or foam as you stir.
  9. ​For best results, allow the solution to age several hours or even overnight before use.
​
Assemble large bubble wand

  1. Cut 2 lengths of cord or rope, 1 twice as long as the other.  For your first large wand, 18" and 36" lengths should work well.  As you gain more experience and want to make really large bubbles you can use longer cords.
  2. Tie each end of the shorter cord securely to the loops of your garden stakes.
  3. Thread a hex nut or a couple washers onto the longer cord, then securely tie each end to the garden stakes as you did in Step 2.  
  4. Holding a garden stake by the free end in each hand (i.e. with the loop/cords on the opposite ends), separate them until the top (shorter) cord is straight and the bottom (longer) cord hangs below (due to the weight of the hex nut) forming a triangle shape.

Assemble small bubble wand

  1. Cut a length of string or yarn about 4 times the length of your drinking straws.
  2. Thread the string through each of the straws, then tie the ends of the string together with a small knot.
  3. Holding a straw in each hand, slide them around the string to make a square window frame, with straws on the left and right sides and string on the top and bottom sides.
​
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making giant bubbles

  1. It's much easier to make giant bubbles if there is no wind, but if there is a breeze, stand with your back to the wind.  Be prepared to turn your body if the wind changes direction.  
  2. Holding the end of a wand handle in each hand, bring your hands close together so that the cords are touching and dangling straight down in a straight line.
  3. Carefully dip the cords into your soap bucket, trying not to tangle them.  If the cords are dry (i.e. the first time you use your wand) you may want to let them soak in the soap solution for several seconds so they can absorb plenty of water.
  4. Slowly lift your wand straight up and out of the soap solution, keeping your hands close together and the cords touching.
  5. Holding your hands as high as you can, slowly open the wand completely by moving your hands apart.  If there is no wind, slowly walk backwards to create enough air flow to start blowing a bubble.
  6. To release and launch your bubble so that it can float away, slowly close your wand by moving your hands close together again.
  7. If your bubble pops, try again.  Making really big bubbles takes practice, but it's lots of fun while you're learning!
​
what's happening
Did you know that water molecules are actually very sticky?  You've probably seen them clinging to lots of surfaces like walls, windows and tables.  When one material sticks to another we call it adhesion, and water molecules adhere or stick to many other materials, but they also like to stick to other water molecules.  When a material sticks to itself we call it cohesion.  If there is no good surface around for water to stick to it's perfectly happy sticking to itself by pulling on several other water molecules nearby.  In fact, each water molecule pulls so hard on the others around it that all of the water tries to pull itself into one tight spherical ball if it can't find anything else easier to stick to.  This force is sometimes called surface tension.  Pour some water onto a freshly waxed car or tabletop and it forms lots of little droplets or "beads" because it can't stick as well to the waxy surface (check the video link at the end to see what water does on the International Space Station).   If you pour it on most other surfaces, however, it will spread out if it can stick to those surfaces.

Okay, so what's all this have to do with soap bubbles?  A bubble is like a balloon, with a thin film or skin on the outside surrounding and trapping air (or some other gas) inside.  Water doesn't stick to air though, leaving only other water molecules for it to stick to, but the surface tension of water, or the force with which it pulls on other nearby water molecules, is so strong that it will form small beads full of water (like raindrops) rather than stretching into a thin film.  If we want to stretch water into a thin skin to make a bubble we need to add something else that it would rather stick to, and that's exactly what soap does.  Soaps and detergents are usually long snake-like molecules with one end (let's call it the head) that likes to grab or pull on water molecules while the other end (tail) likes to get as far away from water as possible (or if possible grab something very different like oil or grease, which, by the way, is what makes them so good at cleaning dirt).  

The head ends of soap molecules in your bubble solution grab onto water molecules, but since their tail ends want to get out of the water at the same time, they can only grab one side so that their tail ends can remain in the air.  Other soap molecules can also grab onto the same water molecules but from the opposite side, while also keeping their tail ends in the air.  This leaves the water molecules free to grab some other water molecules, but only in a region where there is no soap, forming a thin three-layer film skin.  You can think of these three layers sort of like a peanut butter sandwich, where the pieces of bread on the top and bottom are the soap layers and the peanut butter inside is the water.  The surface tension of the water layer inside gives the skin of your bubble its strength, while the soap layers above and below weaken the surface tension just enough to allow the water to stretch out into a thin film so that you can blow a bubble.  Materials like soap that reduce the surface tension of water (or other liquids) in this way are called surfactants.

The soap-water-soap film may be strong enough to form a skin of a bubble but it's also very, very thin- thinner than the hair on your head- so there is a limit to how big a bubble you can make with just the cohesive force of water holding it together.  Making it any bigger and the skin will break, popping the bubble.  The guar gum (or cornstarch) you added to the water gives it extra strength to make even bigger bubbles.  The baking powder also helps by controlling pH or acidity of the solution.  You may have seen some soap bubble recipes that add glycerine to the soap, which works by slowing the evaporation of water (although most bubble experts agree that recipes like ours work much better).  Reference links at the end explain in more detail how these ingredients work.  

variations and related activities
Try blowing a small bubble inside one of your big bubbles.  To do this get as close as you can to the big bubble without touching it, then gently blow a puff of air into the wall of the bubble (see the video).

Why do bubbles pop?  Remember that the skin of a soap bubble is very thin, and it's only the water layer which really holds the bubble together as the soap layers on either side actually weaken the water's cohesive forces or surface tension.  As the layer of water evaporates the skin of the bubble gets thinner and thinner until the water molecules can no longer hold onto each other and the bubble pops.  Do you think your bubbles would last longer on a hot and dry day, or a cool and humid day?

​Of course a bubble also pops when you touch it- that is if you touch it with your dry finger or something else that draws the water out of its film just like evaporation does.  If you dip your finger or hand into the soap solution you should be able to carefully push it through the skin of the bubble and pull it back out without popping it.  You can even catch and hold a bubble in your hand (as long as your hand is completely wet- touch it with any dry skin and it will pop.  

How can a triangle or square shaped bubble wand still make spherical (ball-shaped) bubbles?  Once you release your bubble from the wand you may have noticed that it quickly formed a more  spherical shape.  This is because a sphere is the most stable shape for a bubble, allowing it to enclose the most air while using the least amount of soap (mathematicians might say enclosing the maximum volume with the minimum surface area).  Huge bubbles have a large amount of water in their skins, however, and as gravity pulls on this water (as well as any wind blowing on the bubble) the relatively heavy skin gets tugged quite a bit, which is why the bubble wobbles and changes shape a bit as it moves, but it still tries to remain mostly spherical.

Did you also notice how colorful your bubbles are (look at the photo above)?   In fact, the different colors form rainbow-like stripes that circle around the bubble (although the colors here are formed in a different way than they are in a rainbow).  These colored stripes are called interference fringes and caused by light rays reflecting off the thin soap-water-soap film of the bubble.  Some light rays reflect off the outside surface of the film and back to your eyes while others pass through this surface, into the film itself, and then reflect off the inside surface and then back to your eyes.  When these various light rays recombine on the way to your eyes we say that they interfere with each other.  This also happens when light rays strike a pane of window glass, but the soap film of the bubble is much, much thinner.  In fact, the thickness of the soap film is close to the wavelengths of light, so that this interference creates colored bands as the 
thickness of the film changes, which is why the colors change as the bubble slowly evaporates and its skin gets thinner (check out the references at the end to learn more about the physics of light).  Gravity also pulls the water in the bubble downward, so that it's skin is thicker near the bottom.  Thus the fringes or bands of color indicate changes in film thickness similar to how the lines on a contour map indicate elevation changes.  

references and links to more information
Just about everything you ever wanted to know about soap bubbles:
  • https://soapbubble.fandom.com/wiki/Soap_Bubble_Wiki
  • https://www.exploratorium.edu/search/bubbles
  • https://soapbubble.dk/en/articles
  • https://www.popularmechanics.com/science/a30781401/bubble-math/
  • https://arstechnica.com/science/2020/02/physicists-determine-the-optimal-soap-recipe-for-blowing-gigantic-bubbles/

How does soap work, and what is the difference between soap and detergent?:
  • https://www.thoughtco.com/how-dos-soap-clean-606146
  • https://sciencetrends.com/science-behind-soap-works-make-clean/
  • https://explorationclean.org/science

Experiments and other activities with surface tension and soap:
  • https://www.scienceworld.ca/resource/catch-bubble/​
  • http://www.planet-science.com/categories/under-11s/chemistry-chaos/2011/06/soap---how-does-it-get-things-clean.aspx
  • https://www.york.ac.uk/res/sots/activities/soapysci.htm
  • https://www.teachengineering.org/lessons/view/duk_surfacetensionunit_less1
  • https://www.homesciencetools.com/article/how-to-make-super-bubbles-science-project/

Surface tension of water in space:
  • https://mashable.com/2015/10/13/water-blob-space/

Why are bubbles round?:
  • https://www.scienceabc.com/pure-sciences/why-are-bubbles-round.html
  • https://brilliant.org/wiki/math-of-soap-bubbles-and-honeycombs/

Colors in soap bubbles (and rainbows, just for fun):
  • https://www.exploratorium.edu/ronh/bubbles/bubble_colors.html
  • https://www.explainthatstuff.com/thin-film-interference.html
  • https://micro.magnet.fsu.edu/primer/java/interference/soapbubbles/
  • https://science.howstuffworks.com/nature/climate-weather/storms/rainbow2.htm
  • https://en.wikipedia.org/wiki/Rainbow
  • https://www.rookieparenting.com/make-your-own-rainbow-science-experiment/

Subject Tags
​
  • Bubbles
  • Soap​​
  • Water
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A Fizzy Lava Lamp

6/30/2020

1 Comment

 


​This bubbly experiment combines principles of chemistry, density and buoyancy to create a colorful Lava Lamp look-alike that may be even more fun than the real thing!
Click and expand the tabs below to get started.
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What you'll need
  • Tall plastic beverage cup or jar
  • Vegetable oil
  • Food colors
  • Alka-Seltzer tablets (or equivalent)
experimental procedure
  1. Fill your cup about 3/4 full with vegetable oil.
  2. Slowly add water to the cup and watch the droplets sink through the oil until there is about a 1" layer of water in the bottom of the cup.
  3. Add a couple of drops of food coloring to the cup.  They should sink through the oil and burst once they reach the water layer.
  4. Break an Alka-Seltzer tablet into 4 or 5 smaller pieces.
  5. Drop one of your Alka-Seltzer pieces into the cup and enjoy the show!  When the bubbles stop, drop another piece.
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what's happening
 You may have heard someone say that water and oil don't mix.  The molecules (the arrangement of atoms that make up these chemicals) that make up water are very different from molecules that make chemicals like vegetable oil.  Water molecules (or H2O) attract other water molecules and oil molecules can (weakly) attract other oil molecules, but water molecules strongly repel oil molecules, kind of like the way magnets repel each other if you point the north pole of one towards the south pole of the other.  Thus when you add oil to water they will separate into different layers, and the oil layer will float to the surface because oil is less dense than water.  This is the scientific term which means that a cup of water has more mass (and is therefore heavier) than the same cup filled with oil.  The force that causes the oil to float above the water layer is called the buoyant force or just buoyancy.  Since the food coloring is dissolved in water, these drops also will not mix with oil and sink to the bottom of your cup where they burst and mix with the water to color it.   

The solid Alka-Seltzer pieces are more dense than the oil or the water, so they sink all the way to the bottom.  As soon as they reach the water they begin to dissolve and a chemical reaction takes place between two of the ingredients that produces carbon dioxide gas bubbles.  As these bubbles rise they pull some of the water along with them and have enough buoyancy to rise through the oil layer, but once they reach the surface the bubbles pop and the gas escapes.  Now the water droplets are too heavy to float, and they fall back through the oil where they may pick up another gas bubble to rise again.

This process resembles the rising and falling bubbles in a Lava Lamp, but it works a little differently.  A real Lava Lamp also contains two immiscible liquids (i.e. they don't mix) with different densities, but it uses the energy from a light bulb underneath to warm the lower liquid.  As it warms it expands and its density decreases, allowing bubbles  to rise up through the upper liquid.  As these bubbles float higher (and farther away from the heat source) they cool down, become denser once again, and fall back into the lower layer where the process can repeat.  The upper liquid also warms during this process, but it was carefully chosen so that its density does not decrease as much, so that it still provides enough buoyant force to push the bubbles from the lower liquid upwards.  See the reference link below for a more detailed explanation.
variations and related activities
  • Instead of a tall cup, you can use a soda bottle for this experiment, then simply screw on the cap to store it between uses.
  • There is another different version of this Lava Lamp which uses salt instead of Alka-Seltzer tablets (see reference link below).  For this variation you first fill your tall glass about 3/4 full of water, then add enough oil to form a layer on top of the water about 1" thick.  Now add a couple spoonfuls of salt which sinks to the bottom of the glass (because it's much more dense than the oil or water), but as it does it drags some of the oil with it.  Now watch as the salt begins to dissolve in the water, releasing the attached oil to float to the surface.  This version is not as colorful (unless you like the yellowish color of the oil), but you can jazz it up it if you have oil-soluble food colors.
  • Another really cool buoyancy experiment is the Dancing Raisins (see reference link below)
references and links to more information
Alternative Lava Lamp experiments:
  • https://sciencebob.com/blobs-in-a-bottle-2/   (Lava Lamp bottle)
  • https://youtu.be/XGgC-S9trD4   (uses salt instead of Alka-Seltzer)

How real Lava Lamps work:
  • https://home.howstuffworks.com/lava-lamp.htm

​More about the differences between and oil and water molecules:
  • https://www.thoughtco.com/why-oil-and-water-dont-mix-609193
  • https://www.thoughtco.com/examples-of-polar-and-nonpolar-molecules-608516
  • https://www.scientificamerican.com/article/mix-it-up-with-oil-and-water/

Try some cool density column experiments:
  • https://www.stevespanglerscience.com/lab/experiments/density-tower-magic-with-science/
  • https://www.stevespanglerscience.com/lab/experiments/oil-and-water/

More about density and buoyancy:
  • https://gosciencegirls.com/density-science-for-kids/
  • https://mocomi.com/buoyancy/
  • https://sciencing.com/teach-buoyancy-grade-school-children-8159938.html
  • https://www.khanacademy.org/science/physics/fluids/buoyant-force-and-archimedes-principle/a/buoyant-force-and-archimedes-principle-article

More cool buoyancy experiments:
  • https://funlearningforkids.com/dancing-raisins-science-experiment-kids/
  • ​https://www.coolscience.org/cool-physics/cartesian-divers  (our Cartesian Divers experiment)

Subject Tags

  • Bubbles
  • Density
  • ​Kitchen Science
  • Oils
  • ​Water

​Return to Main Menu

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Colorful Fireworks in a Jar

6/30/2020

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Picture


​These may not be the explosive rocket type you're accustomed to, but this colorful experiment sure looks cool, and it's a great way to celebrate the 4th of July (or any other day) with a little chemistry and physics!
Click and expand the tabs below to get started.
What you'll need
  • Tall plastic beverage cup, jar, or even better​ a large plastic container like those used for pretzels or other snack foods
  • Small cups or bowls (single serving pudding or applesauce cups work well)
  • Small spoon
  • Small fork or toothpick
  • Vegetable oil
  • Food colors
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experimental procedure
  1. Fill your tall drinking cup or other large container nearly full of cold tap water.
  2. Carefully pour just enough vegetable oil onto the water to create a thin oil "slick" that covers most of the surface of the water.  The oil will form little puddles, but it's not necessary for these puddles to cover the entire surface.  Set it aside for now.​
  3. Pour about 1 teaspoon of vegetable oil into a small cup.
  4. Add 1 drop of food coloring to the oil, then using a toothpick or small fork gently poke at the food color to break it into several smaller droplets.  Don't stir- you don't want to mix it, just break it up a bit.
  5. Using more small cups, repeat Steps 3 and 4 with your other food colors.  [You can put all of your colors into a single cup if necessary, but try not to mix the colors together (unless you want to create a new color) as you break up the droplets.
  6. Very carefully pour the contents of one of your small cups (oil and food color droplets) onto one of the oil slick puddles on the surface of your water container from Step 2.  Try to move as you pour so that the food color droplets are not all in one place.
  7. Repeat Step 6 with any other small cups of oil and color droplets.
  8. Observe what happens as the color droplets sink through the oil layer and into the water below.
Picture
Oil puddles on water surface (Step 2)
Picture
Breaking up color droplets (Step 4)
What's happening
You may have heard someone say that water and oil don't mix.  The molecules (the arrangement of atoms that make up these chemicals) that make up water are very different from molecules that make chemicals like vegetable oil.  Water molecules (or H2O) attract other water molecules and oil molecules can (weakly) attract other oil molecules, but water molecules strongly repel oil molecules, kind of like the way magnets repel each other if you point the north pole of one towards the south pole of the other.  Thus when you add oil to water they will separate into different layers, and the oil layer will float to the surface because oil is less dense than water.  This is the scientific term which means that a cup of water has more mass (and is therefore heavier) than the same cup filled with oil.  The force that causes the oil to float above the water layer is called the buoyant force or just buoyancy.

Since the food coloring is dissolved in water, it also will not mix with oil and sinks to the bottom of your cup.  When you gently pour the oil and color droplets from your cup onto the surface of the large container they first mix with the rest of the oil floating on the surface and the color droplets start to sink.  As they reach the bottom of the oil layer they cling there for a few seconds until they can finally break through into the water below.  Once they make it into the water the food color droplets can begin to dissolve, and because they are just slightly more dense that the rest of the water (the food coloring chemicals give it a little more mass) they slowly sink and create the beautiful color streaks that look sort of like fireworks exploding in slow motion!
variations and related activities
What difference does it make if you use hot water instead of cold water?  For a bigger "explosion", try carefully adding a drop of food color directly to the oil puddle on the surface, but don't get too much color in the water or you won't be able to see what's happening.

You can learn more about density and buoyancy by making a density column, where several different (usually colorful) liquids are carefully poured into a tall container where they separate into many layers.  Check out the links below to try this experiment for yourself.

There are several other fun activities and experiments which demonstrate buoyancy, like the Cartesian Diver bottle and Dancing Raisins.  See the links below to have some fun.
references and links to more information
More about the differences between and oil and water molecules:
  1. https://www.thoughtco.com/why-oil-and-water-dont-mix-609193
  2. https://www.thoughtco.com/examples-of-polar-and-nonpolar-molecules-608516
  3. https://www.scientificamerican.com/article/mix-it-up-with-oil-and-water/

Try some cool density column experiments:
  1. https://www.stevespanglerscience.com/lab/experiments/density-tower-magic-with-science/
  2. https://www.stevespanglerscience.com/lab/experiments/oil-and-water/

More about buoyancy:
  1. https://mocomi.com/buoyancy/
  2. https://sciencing.com/teach-buoyancy-grade-school-children-8159938.html
  3. https://www.khanacademy.org/science/physics/fluids/buoyant-force-and-archimedes-principle/a/buoyant-force-and-archimedes-principle-article

Try some cool buoyancy experiments:
  1. https://funlearningforkids.com/dancing-raisins-science-experiment-kids/
  2. http://www.sciencemadesimple.co.uk/activity-blogs/ketchup_diver
  3. https://www.kiwico.com/diy/Science-Projects-for-Kids/3/project/Cartesian-Diver/2649
  4. https://sciencebob.com/make-a-cartesian-diver/
  5. https://www.wikihow.com/Make-a-Spinning-Cartesian-Diver

​

Subject Tags


  • Density
  • Kitchen Science
  • Oils
  • ​Water



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Mentos and Soda and Candy, Oh My!

6/1/2020

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We all know that Mentos and Diet Coke make a grand and glorious mess when they are mixed together.  But why stop there?  Do other candies make Diet Coke erupt too?  Do Mentos make other soda pop erupt as well?  Let’s find out!

Click and expand the tabs below to get started.
What YOu need
  • Mentos
  • Other small, hard or semi soft candies such as Tic Tacs, M&Ms, Altoids
  • Diet Coke (or the generic equivalent)
  • ​Other diet sodas (of course, you can use regular soda too, but diet sodas are less sticky)

​
Picture
experimental procedure version 1

There are two versions of this experiment - Mentos and Diet Coke vs. Mentos and other diet sodas and Mentos and Diet Coke vs. other candies and Diet Coke.  The reason that there are two versions of this experiment is that scientists usually only change one thing (called a variable) at a time.  So, one version changes the soda that is used, and the other version changes the candy that is used.

Version 1 - Mentos and Diet Coke vs. Mentos and other diet sodas

  1. Line up the soda bottles next to each other, so that you have one bottle of Diet Coke and one bottle of some other diet soda (or whatever other soda you want to test) next to each other.  This way, you can see which one erupts higher.
  2. Drop in the same number of Mentos  (4 is a good amount for a two liter bottle) into the Diet Coke and the other bottle of soda at the same time.  Which one goes higher?
  3. Repeat with any other sodas that you want to test.  Be sure to have a bottle of Diet Coke to test with each other kind of soda, so that you have something to compare it to.  Scientists call this a control, because we know what will happen with the Diet Coke and Mentos, and we are comparing that to what will happen with other sodas.
​
experimental procedure version 2
  1. Line up the soda bottles next to each other, so that you have two bottles of Diet Coke side by side.  
  2. Have four Mentos, and about the same amount of whatever other candy you want to test ready to dump in the soda at the same time.
  3. Compare the height of the eruption produced with each candy.
  4. Repeat with all the types of candy that you want to test.
What's happening
It's all about the bubbles.  Have you ever been pranked by someone who secretly shook a can of soda pop before giving it to you to open?  Why does the can explode in a fountain of sticky foam?  The foam is the liquid from your drink plus lots of bubbles containing carbon dioxide gas added when the soda pop was made, and is what make carbonated drinks so fizzy.  This carbon dioxide gas actually dissolves into the liquid soda pop (just like when you stir sugar or salt into water), and manufacturers are able to dissolve much more carbon dioxide- making it even fizzier- by pushing gas into the can or bottle under very high pressure before sealing it.  This establishes an equilibrium, with the  ratio of the number of carbon dioxide gas molecules at the top of the can to the number of molecules dissolved into the flavored water below remaining constant.  When you open your drink, however (without shaking it first), the gas at the top quickly escapes (that's the "pssst" sound you hear) but this also disturbs the equilibrium.  This sudden drop in pressure forces a lot of the dissolved carbon dioxide to come out of solution and form gas bubbles in the liquid which quickly float to the surface, pushing some liquid with them and forming a layer of foam.  But it takes a lot of energy to initially create a gas bubble inside the liquid, as carbon dioxide molecules must push water molecules- which are strongly attracted to each other- out of the way, so most of the energy available is quickly used up.  This means that the bubbles remain fairly small, there isn't much foam, and you don't make a mess.  

You can't (usually) see what's happening inside a sealed aluminum can, but when you shake it the energy you add creates lots and lots of tiny bubbles (see the related activity below).  Now when you open the can the gas at the top quickly escapes, and just as before, much of the dissolved carbon dioxide comes out of solution as gas molecules.  But this time they don't need to waste their limited energy forming the bubbles, as your shaking has already created lots of tiny "starter" bubbles in the liquid, so all this extra carbon dioxide gas easily moves into these little bubbles, making them grow much bigger, much faster.  Bigger bubbles float to the surface faster, pushing a lot more liquid with them, and you get a foamy explosion!  BTW- if your can of soda is very warm you may not need to shake it to make a mess.  Can you guess why?

Shaking the can or bottle is one way to create a bubbly mess, but there are other ways, and some work MUCH better, as you saw in this experiment!  There are actually several different reactions happening at the same time to create bubbles when you mix Mentos with Diet Coke, and not all scientists agree about all of them, but here are the basic ideas.
  1. Nucleation sites - There are very tiny microscopic pits or dents in candy coating of the Mentos.  In our case the scientific word for such things is nucleation sites.  These are places where the chemicals in the soda can get together with the chemicals in the candy, and a reaction will occur to form a bubble.  The reaction that is occurring in this case is that carbon dioxide gas is being released from the soda very quickly, and so it comes bubbling out the top of the bottle.
  2. Carbon Dioxide gas - This gas is dissolved in soda, and it is what makes soda fizzy.  When the chemicals in the soda and the chemicals in the candy mix together at the nucleation sites, this gas comes out of solution to form bubbles in the soda really quickly, and causes the eruption that we all love to see.
  3. Aspartame - Aspartame is a chemical that tastes sweet, but doesn’t have calories, like sugar does.  It is a reactant in this reaction, which means it helps to make it happen.  If you don’t have aspartame in your soda, you may not have as much of an eruption.  This is another reason that diet soda might work better than regular soda, because regular soda does not usually have aspartame.
  4. Caffeine - Caffeine is a chemical in some soda that gives some people more energy.  It also makes these chemicals react better with each other.  So, if you use a soda that has no caffeine, you may not have as high of an eruption.  However, if you have a soda that has more caffeine, you might get a higher eruption!
  5. Potassium benzoate - This is a preservative, and is supposed to make the soda taste better for a longer period of time.  However, it also helps the chemicals react better with each other, and so sodas that do not have potassium benzoate might not react as well
  6. Gum arabic - Gum Arabic helps to make the Mentos chewy.  It also helps to make this reaction go faster.  You might want to look at the ingredients on other candies to see if you can find gum arabic on their ingredient list.
  7. Gelatin - Gelatin is also a reactant, and also in other candies besides just Mentos.  Check the label!

All of these things together combine to produce the reaction that we know and love when we put Mentos and Diet Coke together.  However, does that mean that the reaction between Mentos and Diet Coke is the best that it can possibly be?  Not necessarily!  What if you find a soda that has more of one of these reactants (like caffeine)?  Experiment with these variables, and see what you can find out!
variations and related activities
Rock salt (like you put on the sidewalk to melt ice) also reacts well with Diet Coke.  Try it.  You may also want to try granular salt (i.e. what's in your kitchen salt shaker).  Does it work as well (it's exactly the same chemically)?  Hint- think about the nucleation sites.

What if the hole that the carbon dioxide and soda came through was smaller?  What would happen to the height of the bubbles?  Remember, however, that pressure is building up in the bottle, and that it has to get out somewhere.

You can't see what happens inside an aluminum can of soda pop when shaken, but you can see through most plastic bottles.  Try shaking a bottle of clear soda pop (like 7-Up, Sprite or Ginger Ale) to see all the tiny bubbles created.  Unscrew the cap quickly and  you will get a foamy mess.  What happens if you wait until all of the bubbles float to the surface and pop before opening the bottle?


The wrinkles in raisins are also very good nucleation sites for carbon dioxide bubbles to form in soda pop.  Try adding 5 or 6 raisins (fresh ones work best) to a bottle or tall glass of a clear soda pop like 7-Up, Sprite or Ginger Ale.  You probably won't get an explosion, but there will be bubbles and you may be surprised what they do to the raisins!  Look for a new experiment page soon that will explain what's happening (or see the links below), but we think you can figure it out if you observe carefully.
​
References and links to more information
https://www.youtube.com/watch?v=zGMxEr2AxHM 
This is the Mythbusters episode that deconstructs what happens when you put Mentos in soda.  Parent note: There are a few shots of Kari Byron wearing a swimsuit that are a bit revealing, but other than that, the science explored here is well done and well tested.


https://www.youtube.com/watch?v=fBkbWKFv2pE
The original Eepybird video using Diet Coke and Mentos, which some people say started the craze.


https://www.eepybird.com/featured-video/coke-and-mentos-featured-video/science-of-coke-mentos 
More explanation from Eepybird.


https://www.acs.org/content/acs/en/education/whatischemistry/adventures-in-chemistry/experiments/mentos-diet-coke.html
Explanation from the American Chemical Society.


https://www.stevespanglerscience.com/lab/experiments/original-mentos-diet-coke-geyser/
Steve Spangler has some ideas about how to take this further, as well.

http://www.appstate.edu/~coffeyts/DietCokeandMentos.pdf
A bona fide scientific study of what is happening and why.

https://www.scientificamerican.com/article/why-does-a-shaken-soda-fi/
https://www.scienceabc.com/pure-sciences/why-a-soft-drink-bottle-fizzes-when-opened.html
https://chemistry.stackexchange.com/questions/40502/why-does-soda-pop-after-shaking
https://www.stevespanglerscience.com/lab/experiments/soda-can-shake-up-experiment/
https://www.livescience.com/34159-tap-soda-can-carbonation.html​
https://www.snopes.com/fact-check/on-tap/
More explanations of what happens when you shake a can of soda.  Some people think there is a trick to keep a shaken can from exploding, but others think it's a myth.  Maybe you should try to confirm or bust the myth!  Does this apply to plastic bottles too?

​https://funlearningforkids.com/dancing-raisins-science-experiment-kids/
https://www.thoughtco.com/the-dancing-raisin-science-experiment-2086765
https://www.stevespanglerscience.com/lab/experiments/dancing-raisins-the-bubble-lifter/​
Adding a few raisins to a glass of soda pop is a lot more fun than you may think!

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