Posts tagged: chemistry

Kitchen – Non-Newtonian Fluid; aka “Oobleck!! – (Weekly Unplugged Project)

By , November 10, 2008 10:00 pm

Today, along with a visiting friend, we finally got to do this week’s kitchen Unplugged Project.  We used cornstarch, a common kitchen ingredient, to create a non-Newtonian fluid.  The other name for such a mixture is Oobleck, from the Dr. Seuss book, Bartholomew and the Oobleck.

It was SO COOL!!  The kids and I found it fascinating!  I was so enthralled that I felt that the mess (and there WAS mess), was actually very worthwhile.

I set out four small mixing bowls and spoons, one for each child.  I also set out water, cornstarch, and measuring cups.

The kids each put about one cup of cornstarch into their bowl.

I had them add water just a bit at a time,

and stir until we got the “right” consistency.

It was probably close to about a half to two thirds of a cup of water, but the “right” consistency was quite obvious.  When the mixture starts to feel hard to stir although it looks like liquid on the top, then it is probably about ready.

Test it by dipping your hand in, lifting out some fluid, and squeezing it into a ball.  It should feel like a hard, dry ball in your hand but when you open your fingers, it will turn back into a liquid and run back into the bowl.

Here is a fleeting picture of it as a solid:

Adjust your mixture by adding a bit of water if too dry, or a bit of cornstarch if too wet.  You’ll know you have it right when the oohs and aahs begin!

This was so much fun to play with and was a very weird sensation that is quite hard to describe.  The children (including my 2 year-old) and I played for maybe an hour:  squeezing, stirring, punching, and even hammering!

My favorite trick: If you roll it between your two palms as if you are making a ball with clay, it makes a nice solid ball, but as soon as you release the pressure, it all runs away!

Also, put a finger gently into it and it will slowly and strangely be sucked under as if in quicksand.  Jab the finger in quickly, and it will hit a hard surface.

The Science:

As I understand it, when you squeeze the mixture, or compress it quickly in some way (hammer, punching, etc.), the molecules compress and become a solid.  When the pressure is released, the molecules spread out again and the mixture becomes a liquid.  As my oldest daughter said:  “Oooo!  I can feel it changing from a solid to a liquid!”

Here are two good explanations of what a non-Newtonian fluid is:

“Oobleck is often referred to as a ‘non-Newtonian’ substance because it does not behave as Newton’s Third Law of Motion states; for every action, there is an equal and opposite reaction. Applying this principle, you would expect Oobleck to ‘splash’ when you ‘smack’ it with your hand. (Smacking is the action, splashing is the reaction.) However, when you try this out Oobleck does not splash, in fact, it becomes a solid substance for a few moments.”

(from Oobleck – a Non-Newtonian Fluid)

or

“Isaac Newton defined normal liquids as having consistent flow behavior affected only by temperature or pressure; so fluids that change their resistance to flow (viscosity) under stress are not ‘normal’. Some of these fluids get runnier when stress is applied, like paint, toothpaste and slug mucus. Some get thicker, like quicksand and Oobleck.”

(from Science in the City – Bullet Proof Goo)

As to why it behaves this way, it seems that this is actually a matter of some controversy, but here are some links that are more knowledgeable than I:

Oobleck –  a Non-Newtonian Fluid

More About Liquids: Thick and Thin

Fun:

You can actually walk on this stuff!  My son wanted to try it after seeing this You Tube video.

(There are a few other walking on cornstarch videos out there if you are really into this!)

Tips:

1) I STRONGLY recommend that you either do this outside in an area that you can just hose off afterwards, or use a vinyl tablecloth that you can remove and hose off afterwards.  Why didn’t I use mine?

2) Be sure to add the water a bit at a time, it is easy to overdo it.

3) If you do forget the tablecloth like I did, you will find that non-Newtonian fluids can be difficult to clean off a table.  When you try wiping what looks like liquid, it turns into a solid and sticks.

When you stop scrubbing it returns to a liquid state!  After a bit of frustration I used my science brain and poured water on the table.  I was able to wipe the now runny cornstarch liquid into a trash can.

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Although I suggested it humorously yesterday, I have actually had several votes for an Unplugged Project theme next week involving “sort, trash, junk, donate.”  Well, why not??

As Captain Jean-Luc Picard would have said (see, I haven’t always been without a TV!):  “Make it so.”

Let’s call next week’s theme:

Sort-Junk-Donate

Remember, the theme can be loosely interpreted if you don’t feel like cleaning your house this week.  Just be creative and have fun!

Molecules in Motion (“730 Easy Science Experiments” – Book Review)

By , September 22, 2008 10:45 pm

I must admit, my heart sank when my sister gave my kids the book 730 Easy Science Experiments: With Everyday Materials by E. Richard Churchill, Louis V. Loesching, and Muriel Mandell.

This confession will certainly earn me yet another “Mom of the Year Award,” but here it is:

Was my first thought:  “730?? Oh hooray! Think of all the wonderful projects and what we will learn together!!”  Noooo…. My first thought was:  “730?? Who is going to have to do those 730 science experiments with them?? Oh no!”

My childless sister seemed to pick up on my silent consternation and left with a sadistic smile (or so I thought) and the parting words of: “Have fun!”

Well actually, we are having fun.  The book sat on a shelf for a while until my 8 year-old daughter recently rediscovered it.

On Sunday, when I was planning a “Fun With Mom Day,” she showed me some experiments that she wanted to do.  Since we were going to have Fun With Mom no matter what, I was willing to assist in any and all experiments.  We did several.  The one I will share with you today involved the motion of molecules.

This sounds fancy, but actually, like most of the experiments in this very thorough (did I tell you already that there are 730 experiments?) volume, this experiment involved only items we had on hand here in the house.

You need food coloring, two clear glasses, and hot and cold water.  Put hot water in one glass (I used very hot tap water) and cold water in the other (I used super-cooled water from our refrigerator water dispenser).

Put just one drop of food coloring in each glass and watch what happens.  The molecules are moving faster in hot water so the food coloring blends with the water very, very quickly.  In the slower-moving cold water glass, the food coloring barely moves at all.  In fact it makes some beautiful slow-motion droplet shapes that reminded me of a lava lamp.

This glass was the hot water:

And this one was cold (see the “lava lamp?”):

This was just one of 730 experiments.  That means I have another 729 to inflict on you all!!

Seriously, I do like this book.  As I mentioned earlier, the ingredients are mostly household items, or are easily obtainable: no enriched uranium needed here.

The experiments vary in complexity from ridiculously simple yet not boring for young ones (Straw Wheels – moving a heavy book more easily using drinking straws as rollers – p.23) to more complicated yet still easily doable (Seeing Sound Waves p.110 or Balloon Barometer p.249).

The chapters are interesting and fun:  Clutching at Straws; Paper Capers; More Than Lemonade; Dairy Dozen; Adventures With a String; Soap Suds; Slow Start-Fast Finish; Keeping Your Balance; How to Have All the Moves; The Sound of Science; Feeling Stressed? Try Some Surface Tension; Science Can Give You a Warm Feeling; Blown Away; Being Earth Conscious; World Travellers; Leafy Lessons; Dirty Words: Soil, Sand, Humus, and Mud; Gravity and Magnetism: Attractive Forces; Don’t Fiddle With Old Fossils; Weather; Whirling Winds and Gentle Breezes; Water, Water, Everywhere; Building a Weather Station; Air, H2O, and Other Things; Here’s Superman, But Where’s Clark?; Salty Solutions and Sweet Success

Each experiment has a “What to do,” a “What Happens,” and most importantly, a “Why” section.

You’ll be seeing more experiments from us I am sure.  Remember, we still have 729 of them to show you!

Hot – Edible Sugar Science (Weekly Unplugged Project)

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By , August 11, 2008 7:19 pm

caramel

Finally, here is my hot post that disappeared into the ether last night. Thanks so much to Julie K in Taiwan, Angi and Nature Mama for having the brilliant idea of emailing me the post from their Google Readers. That saved me at least an hour of rewriting! I was so down on computers this morning, but this evening I am uplifted by the fact that three people I have never met in “real life” can help me out! Thank you!!! Now, on to the post:

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The theme for this week’s Unplugged Project was hot. Finally, we managed to get back on schedule and do it, although we broke away from our usual craft project and went in a more scientific direction.

While away this summer, I found a number of good books in my Dad’s favorite thrift store (he’s a packrat too). One is called Science Experiments You Can Eat by Vicki Cobb (more about the book at the end of this post). While we were trying to come up with hot ideas, my 7 year-old daughter picked up this book and wanted to choose a food-related project. We decided on Caramel Syrup: Sugar Decomposes from the Kitchen Chemistry chapter.

Older children will find this scientifically interesting and fun to do. Younger kids will enjoy the end result!

The goal of the experiment is to teach about chemical compounds and how they can sometimes be broken down into completely different substances. Although I always liked science in school, I am not a chemist so forgive me if I am not 100% perfect in my description.

Since I am a terminal nerd, I didn’t trust the book’s very simple explanation, and actually researched sugar and how it decomposes. I learned that sugar and its breakdown process is rather complicated. (If the mysteries of caramelization keep you awake at night, then read this.)

I tried to keep it 7 year-old simple and explained to my daughter that sugar is actually carbon and water fused together. When you heat sugar, it breaks down into its original carbon and water elements. I showed her the scientific formula for table sugar (sucrose): C12H22O11 . She already new that H2O was water and could see that in the formula. After I explained that C meant carbon, she saw the carbon and water in the formula.

Heating the sugar would cause it to become watery (the release of the water) and dark (the carbon). It would no longer really be sugar.

What we needed – sugar, water, a heavy frying pan:

First my daughter poured half a cup of sugar into the frying pan:

We heated the sugar over medium-high heat and my daughter stirred it:

After about 5 to 10 minutes, the sugar started to melt:

As my daughter continued stirring, the sugar melted further and began to darken and become very watery:

Finally it turned “straw-colored” and we had transformed our sugar into a new substance – caramel. We turned off the heat and slowly added half a cup of water in order to create a runny, edible solution. I did the pouring as the caramel was so hot that it steamed and spattered:

The shock-cooled caramel formed a brittle sort of candy-lump that we just had to taste:

My daughter continued stirring the mixture on low heat for about another ten minutes – until the big caramel chunk dissolved into a solution:

This is what we ended up with: a delicious carbon-water mixture that we ate over ice cream!

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If you haven’t heard of Science Experiments You Can Eat and you have scientifically-inclined children (or you homeschool), you might want to check it out of the library. Ours is an old version (1972), but the new one is supposedly revised and updated. I haven’t seen the new one, but our book has the following chapters about the science of food: A Kitchen Laboratory; Solutions; Suspensions, Colloids, and Emulsions; Carbohydrates and Fats; Proteins; Kitchen Chemistry; Plants We Eat; Microbes; and Enzymes.


If you did this week’s hot Unplugged Project, please put your link in Mr. Linky below so we can all find you. If you didn’t, please read how to join in, and consider doing next week’s project.

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Next week’s Unplugged Project theme will be:

Trees

Have fun!

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