Friday, December 19, 2008

A Chemist Bakes the Perfect Cookie

Food Scientist Shirley Corriher's tips for baking perfect cookies seem to be everywhere at the moment. On National Public Radio, her advice for crumbly cookies is to add a tablespoon of water to a cup of flour. That will make the proteins — glutenin and gliadin — hold together. In the New York Times she's one of several culinary experts weighing on why you must keep butter cool.
Butter is basically an emulsion of water in fat, with some dairy solids that help hold them together. But food scientists, chefs and dairy professionals stress butter’s unique and sensitive nature the way helicopter parents dote on a gifted child.
Although I have not heard of Corriher before, I am tempted to check out her new book Bakewise: The Hows and Whys of Successful Baking with Over 200 Magnificent Recipes. Amazon customers give it some rave reviews.

And I like the chemistry angle too.

Friday, December 12, 2008

Cake in a Mug mug


When I couldn't get carbon snakes to work, I made exploding cake in a mug. And for a last-minute holiday gift, I just put the barebones recipe on a mug, complete with crudely drawn illustrations. You can order them too from Cafe Press. Order by Monday for holiday delivery.

Saturday, December 6, 2008

Homemade Ice Cream

We had homemade ice cream for dessert on Thanksgiving. (My dad, never having seen our machine, asked, "Whose home was the ice cream made in?") But the machine we have uses a cooling pan with some kind of chemical sealed inside. You put the pan in the freezer before using it, then just add the ingredients and let the machine stir them up. Not much to it.

Meanwhile, over at Socks and Books, homeschoolers "Moomintroll" and "Snufkin" recently made ice cream the old-fashioned way, using rock salt and ice cubes. We did this years ago using two plastic bags, but they used a metal pot, which I think looks way more dramatic.

Go to their post to see how its done, complete with chemistry explanation. I'm saving this link for future reference!

Sunday, November 30, 2008

Chemistry in the Community online textbook

I came across a discussion on a homeschool email list of the American Chemical Society's high school textbook Chemistry in the Community (ChemCom) and thought I'd throw it out there for anyone interested. The textbook is muy expensive, but there's a companion website with supplementary student material, including animations, that might be useful even if you don't use the text.

And just a reminder that ACS hold Chemistry Week activities every October, and their website has a page of educational content, including simple experiments for kids.

Monday, November 24, 2008

MAKE's Chemistry Gift Guide


At the MAKE magazine website they have a well-rounded if nostalgic collection of chemistry books and sets for "the next generation of chemists." A lot of glassware if you're into that sort of thing; I was very happy using plastic cups and spoons. Worth browsing.

(And if you want to send my family a little holiday cheer, and maybe save a little money, come back here and buy the items you see at MAKE from my Amazon store. Those little kickbacks I get when you click through from my websites are appreciated!)

The Thames and Konos Chem C3000 chemistry set -- probably the best you can buy at the moment, though still less complete than chemistry sets of the 50s and 60s -- is $50 cheaper at Amazon.

Thursday, November 6, 2008

Carbon Snakes


Here's a project I neglected to post last spring. We weren't totally satisfied with the results, so it never made it into the blog. Just this week, however, I found something fun to add, so I'm putting it up now for the record.

This experiment, like so many we did last year, came from Anne Marie Helmenstine at About.com's Chemistry page. Here's what we did:

Baking Soda and Sugar Carbon Snake

Sand

lighter fluid

baking soda

powdered sugar

  1. Mix 4 tsp sugar and 1 tsp baking soda.
  2. Make a mound with the sand. Push a depression into the middle of the sand.
  3. Pour the alcohol or other fuel into the sand to wet it.
  4. Pour the sugar and soda mixture into the depression.
  5. Ignite the mound, using a lighter or match.

Anne Marie goes on to write:

At first, you'll get a flame and some small scattered blackened balls. Once the reaction gets going, the carbon dioxide will puff up the carbonate into the continuously extruded 'snake'. Actually, you don't even need the sand. I tried this project using baking soda and sugar in a metal mixing bowl, added the fuel, and lit the mixture. It worked fine. The old firework snakes had a distinct smell. These have a smell too... burnt marshmallows! If you use pure ethanol, sugar, and baking soda, then there is nothing toxic about this project. One caution: Don't add fuel to the burning snake, since you risk igniting the alcohol stream.
We got the puff balls, but the snakes were kind of stumpy. If you watch the video, you can see that the level of anxiety over this experiment overshadowed the excitement as well:

video

Here's how Anne Marie explains the reaction:

How Black Snakes Work
The sugar and baking soda snake proceeds according to the following chemical reactions, where sodium bicarbonate breaks down into sodium carbonate, water vapor, and carbon dioxide gas while burning the sugar in oxygen produces water vapor and carbon dioxide gas. The snake is carbonate with black carbon particles:

2 NaHCO3 -> Na2CO3 + H2O + CO2
C2H5OH + 3 O2 -> 2 CO2 + 3 H2O

Monday, October 20, 2008

Kitchen Biology


Many of the chemistry projects that we never got to last year lend themselves to investigation under the heading of biology as well. Although I haven't seen the term "Kitchen Biology" used as often as "Kitchen Chemistry," I've got plans to brew (root) beer (with yeast), make yogurt (with bacteria), and grow bioluminescent bacteria on old fish. Good times ahead!

Be sure to visit my Home Biology blog.

Tuesday, September 9, 2008

Wood Sorrel


We've been cataloging plant and animal species in our backyard for biology studies and discovered that wood sorrel has a sour, lemony taste to the leaves because of oxalic acid. This acid is also present in many other fruits and vegetables; in fact, according to Wikipedia, if you eat a slice of rhubarb pie with a glass of milk, it will cause some of the calcium to precipitate out, creating tiny grains you can feel on your tongue!

Saturday, September 6, 2008

Moving on to Home Biology

The summer has gone and I am starting to add content to this year's science blog, Home Biology. Come join me!

Sunday, August 3, 2008

Periodic Table of Videos

Still hoping to do a few outdoor experiments before the summer's over but work -- and unending days of rain -- are making it difficult. Maybe this week...

In the meantime, fellow homeschooling author and blogger Kris Bordessa has post on the Periodic Table of Videos from the University of Nottingham in England. The short videos are hosted by Martyn Poliakoff, research professor and pioneer in the field of green chemistry -- with the best Mad Scientist hair I've seen in a long time!

Kris says her 15 year old spent an hour poring through this site. Check it out!

Sunday, July 13, 2008

Chemistry Simulations vs Hands-On

Note: I'm hoping to post at least a couple more experiments here -- one that we are still trying to get to operate as advertise -- before turning our attention to biology for the coming school year. (I've just set up homebiology.blogspot.com in anticipation!)

But in the meantime I'd like to pass along an email my friend and fellow homeschooling parent Paul Fernhout sent our local homeschool email list today with some thoughts on chemistry simulations:

In regard to something else I am looking into, I found a website today I wanted to share by Professor William J. Vining at the State University of NY at Oneonta. He has helped develop free chemistry simulations that should run in most web browsers with a Shockwave/Flash plugin installed. At least most of the first five or ten simulations in the list at that URL should be easy enough to play with about some basic ideas of chemistry (the periodic table, etc.). I think the simulations all go with a specific text book, but the general concepts would apply for any person interested in chemistry even without a specific textbook. Essentially, these are all safe scientific toys which may (or may not) in turn inspire further interest in the topic of chemistry. So, think of most of them more as chemistry puzzles (what could they mean?) than chemistry instruction.

From Prof. Vining's main page:
My principal interest lies in developing and testing educational materials and methods for chemistry. The materials are primarily computer-based multimedia software systems that serve the dual purpose of simulating the exploratory nature of chemical investigation and also make use of graphical advantages of computer systems to better explain chemical concepts. The focus of these programs is to enable students of chemistry to explore chemical concepts in a manner that leads them to discover those concepts independently. Because chemical concepts are based on analysis of experimental results, the software systems we design are centered around presenting the student with information they would obtain from an experiment, along with computer-based tools for analyzing those results. This allows the student to observe trends and choose the appropriate experiment to answer a particular question. Once an area of chemistry has been presented by an interactive experimental simulation, the concept can then be explained using multimedia tools such as videos and animations. Our work involves preparation of materials appropriate for use in general, organic, inorganic, physical, and analytical chemistry. Recent projects have included work on a CD-ROM textbook for general chemistry and currently we are working on modules for organic chemistry.
He has some other resources linked from his main page, like some videos of mixing chemicals (though the one I tried did not play well for me). He also has some downloadable things (for Windows?) I did not try.

The Concord Consortium is another site with high quality free learning resources related to chemistry and other things as well, including for example CC Atoms. But some of these resources are harder things to try as they require Java and perhaps locally installing some things. Many (but not all) of these resources are designed for college courses, but could be fun to just play with for someone interested in chemistry who at least knew a bit to get
started with.

A chemistry simulation is definitely IMHO a good use of computers for older homeschoolers, since real (sometimes dangerous) chemistry sets are hard to get these days, making chemistry otherwise difficult to really explore in detail at home. There are some nostalgia and warnings there in the comments about old chemistry sets by the way (some had radioactive materials). There is a link in the comments to that blog post to a supposedly interesting set at Edmunds Scientific. But that set is $200 and obviously is going to take some supervision and pose some risks.

Scientific Explorer's Fizzy Foamy Science Kit of Safe Chemical Reactions is an example of a ($20) "safe" chemistry-related set we got for our child (age four) but it mostly just has stuff you'd find around the house like oil, baking soda, and vinegar (except maybe citric acid in pure form): "
A container of oil in it had leaked all over everything when we got it, but it cleaned up easily. It has some scientific looking stuff in it (not sure if it would be cheaper to buy it separately), but is probably not very interesting for older kids for that long.

The simulations let you try to do all sorts of things, although may be mainly of interest to older kids since they are more abstract (that is, no fizzing). Obviously, like all simulations, they are still not the same as the real thing, being worse in some ways and better than others. They will help kids get the intellectual challenge of chemistry, but they won't help them gain a sense of confidence in a lab setting they would get with the real stuff. But even if you had the real stuff, I'd suggest the simulations could still be interesting (perhaps even more interesting for a motivated learner).

Thanks, Paul!

Monday, June 16, 2008

Photosynthesis

I've been subbing in the public schools the last couple months (quite an experience after 10 years of homeschooling, but that's another story). Last week I had to go over plants with a class of third graders and then give them a test.

In the review materials, their teacher had given them the following formula:

CO2 + sunshine + water = food

This really made me nuts. When my kids were a little younger, I made it a point to find out just how plants turned sunshine into food. It took some doing, but I finally found a DK book that spelled out the relevant chemical formula. Which is this:

6CO2 + 12H2O + sunlight ---> 6O 2 + C6 H12O 6 + 6H2 O
or...
carbon dioxide + water + sunlight --->
oxygen + carbohydrate + water

Now, she's already given them a chemical name (CO2 -- I asked and one child identified it as carbon dioxide). She could very easily have then given them H2O, water, and then done the math. The carbohydrate, glucose, is a form of sugar, which they would have readily understood -- especially here in upstate NY, where maple sugaring is common!

Actually, I was surprised to see "sunlight" in the actual formula; it provides the energy via chlorophyll, a green pigment that absorbs energy from sunlight. But most amazing of all --

THERE WAS NO MENTION OF CHLOROPHYLL!

(And photosynthesis was hand-written in on the test as an afterthought; I had to help the students out by letting them know that photo means light and synthesis is making something.)

Just to understand, as with most public-school science in my experience, the information the kids had to know was basically all vocabulary. For instance, they had to correctly label the cotyledon of a seed. Now, I doubt there are many adults who can identify cotyledon but not chlorophyll. Really.

Anyway, here, for the record, is my third-grader-friendly, chemistry-literate explanation of how plants make food. I am looking forward to exploring biology again (my plan for next year) in light of my ever-growing comfort with chemistry.




Wednesday, June 11, 2008

Radioactive Elements


I became interested in radioactive elements after my brush with thyroid medicine, and I started looking on eBay for a cheap Geiger counter. (My dad, who worked with X-ray machines, brought one home and demonstrated it for us when I was a kid -- another example of how early impressions about science can stick with you.) Before I could finish my research, a friend bought one for us. Turns out, what we actually have is a radiation detector intended for survivors of nuclear war. As one site I read said, if this thing shows a reading, evacuate!

So when I wanted to look at some common household radioactive items, we still didn't have anything to measure them with.

(This didn't work.)


So we found some nice videos on YouTube from people who did have real Geiger counters.

Among the radioactive items people collect or have about are:

smoke detectors (Americium)
salt substitute (potassium isotope)
Fiestaware dishes (the famous orange-y red made with uranium)
gas lantern mantles (a favorite of The Radioactive Boyscout)
old luminous watches (radium)

But here in Saratoga Springs, NY, we have one source of radioactivity that is less common: mineral water.

Back in the 1800s, Saratoga was known for its horse racing, its casinos, and its spas. Its many springs, the result of a geological fault which runs right through the center of the city (it's a low point known until recently as "The Gut", but now the source of trendy new restaurants). Apparently radioactivity is one requirement for "really good" mineral water.

The radioactivity comes from radon gas -- the same stuff that accumulates in basements, a by-product of the decay of uranium -- dissolving in the water underground. Once in the air, the radioactivity dissipates quickly, with a half-life of about four days.

Nevertheless, for the sake of science, we took a walk over to the Saratoga Spa State Park and collected a few bottles from the Polaris spring, one that is known to be radioactive. We also took a sip (it's carbonated but pretty sulfurous, so you wouldn't want to drink it regularly anyhow). So far, no one is glowing in the dark.

The radiation detector wasn't a total loss: it came with a really enlightening manual about radiation safety, for perusal in your fallout shelter. This article from the World Nuclear Association is also basic enough for kids. You'll also find all kinds of fascinating information about radiation at Theodore Gray's Periodic Table.

I'm still planning to get a working Geiger Counter, and maybe a few odds and ends from United Nuclear.









Thursday, June 5, 2008

A word from our sponsor


A new chemistry post should be up this weekend, but in the meantime I'd just like to mention that I've just published my first book AROUND THE WORLD CRAFTS: Great Activities for Kids who Like History, Math, Art, Science and More!

The book is a collection of my Hands-on Learning columns from Home Education Magazine.

Enjoy!


Tuesday, May 20, 2008

Shrinky Dink polymers


I pulled out some sheets of shrink film lying around in my art cabinet so we could play with polymers. Polymers are long chains of molecules that can be manipulated in different ways. Shrinky Dink and similar thermoplastics are stretched using heat. When you re-heat them, they revert to their original shape. Here's a handout for kids from the American Chemical Society on making your own shrink film from recycled clamshell containers from the bakery or salad bar. Look for the #6 recycling symbol (other plastics will react in different ways in heat -- including by giving off toxic fumes). Number 6 is for polystyrene, the same stuff that Styrofoam is made out of. You obviously want the hard, thin, clear plastic, not the expanded puffy stuff.

It'd been a while since I played around with these, and I forgot that you have to let them curl up and then uncurl before removing them from the oven.



We popped them back in the oven and they straightened themselves out, with a little help where they had stuck together. Be careful fiddling around with them: when they're soft enough to unbend, they're still pretty hot.

Here's what the kids made:



Shrinkage: 60% (after baking twice)



Shrinkage: 50%

(By the way, it was a great day to be baking things, a brisk 50-something. In May. Helped me hold out against the urge to turn the heat on.)


Friday, May 16, 2008

Extra Oxygen



Lesson: The enzyme catalase splits hydrogen peroxide into water and oxygen.
What Happened: Adding yeast to hydrogen peroxide caused it to foam up with oxygen bubbles, which re-ignited an extinguished splint.

Science educator Robert Krampf has a collection of home science videos -- many but not all about chemistry -- on his website. He recently re-instated his email list, and I decided to try today's Experiment of the Day with some friends who are visiting. You can see Krampf explaining the experiment as he performs it on his website, which I have added to the sidebar. Here is an excerpt:

You will need:


  1. a wooden, cooking skewer
  2. a lighter
  3. 3% hydrogen peroxide (from the grocery or pharmacy)
  4. a cup or glass
  5. yeast

Pour some hydrogen peroxide into the glass. Sprinkle some of the yeast into the peroxide and give it a stir. Very quickly you will see bubbles rising, producing foam on top of the liquid.

Light the end of the wooden skewer, and let it burn for a moment. Then blow out the flame. If you blow gently on the burning end, you should see a red glow. It is still burning, but not flaming. Carefully bring the glowing end of the skewer up to the larger bubbles in the foam. The skewer should flare up, bursting into flame.
We did not get the dramatic results that he gets in the video, but after a few tries we figured out that you need to let the skewer burn for few minutes to get hot enough to reignite.

Here is an explanation of how our bodies use catalase in the same way:
Hydrogen peroxide is a toxic by-product of respiration.  Organisms that
obtain energy by oxidation of foods must develop mechanisms to limit the
damage it causes. This is primarily accomplished by a class of enzymes
called catalases, which catalyze the reaction

2 HOOH --> 2 H2O + O2

Wednesday, May 7, 2008

Surfaces and Density

video

This week we did a number of experiments with oil, water, food coloring and various props to explore the property of surfaces. The physical properties like surface tension and solubility are related to the strength of Intermolecular Forces -- the attractive forces between molecules.

Surface Tension Experiments

These came from the website of the Chicago Section of the American Chemical Society

3 bowls or containers with water
liquid soap
pepper
a piece of string
a paper clip
a fork
a needle

Bowl 1:

1. Sprinkle pepper on the surface of cold clean water in a shallow dish. Allow the particles to spread out and cover the surface.

2. Put your finger in the bowl.

3. Put a drop of liquid soap on your finger. Put your finger in the bowl again.

What should happen: Pepper should rush away from your finger in a star pattern.

What did happen: Pepper rushed away from finger in a circle -- still impressive.

Bowl 2:

1. Float a small loop of string in the middle of the surface of water.

2. Put a drop of liquid soap inside the loop.

What should happen: The surface tension inside the loop of string should weaken by the soap but the surface tension outside the string should have pulled the string outward.

What did happen: The string sank before we could try step 2.

Bowl 3:

1. Lower a paper clip and a needle flat onto the water surface using the fork. They should float.

2. If they don't, place a paper towel on the surface of the water, place the objects on the paper, and then remove the paper.

3. Now put a drop of liquid soap on the water surface.

What should happen: As soon as the tension is broken by the soap, these items should sink to the bottom.

This one worked as planned!

Density Column
Joy of Chemistry, page 131


2 clear glasses or plastic cups
Glycerin
Water
Food coloring
Cooking oil
Liquid soap
Plastic spoon

1. Pour about an inch of water into the cup.

2. Add food coloring to the water.

3. Pour about an inch of glycerin into the second cup.

4. Gently add colored water.

5. Add oil until you get three layers.

6. Stir. Allow to settle.The water will mix with the glycerin, but the oil will separate back out.

7. Add a layer of liquid soap.

8. Stir gently. The oil will mix with the glycerin.

What's Happening: Different liquids have different densities, and according to the density, the liquids will settle in a certain order when mixed. Oil is less dense than water and therefore will settle on top of water.

(NOTE: Glycerin--C3H5(OH)3, which can be bought in drugstores -- can be added to dish soap to make long-lasting bubble solution. Bubbles eventually burst once the layer of water evaporates, but glycerin forms weak hydrogen bonds with water, delaying evaporation. )

Lava Lamp


video

(Sorry that it's sideways. When I figure out how to fix it, I will repost it!)

Tall narrow jar
Water
Food coloring
Vegetable oil
Salt

Directions:

1. Fill the cylinder with water.

2. Add the food coloring. Do not let the water become too dark.

3. Slowly pour oil into the cylinder. It should make a thick layer on top of the water.

4. Slowly sprinkle the salt into the cylinder on top of the oil. The salt coats the oil and causes it to fall to the bottom of the graduated cylinder in globs. The oil will gradually return to the top of the graduated cylinder.

What happened:

Vegetable oil is less dense than water. When the salt is added, it sticks to the oil and drags it down. Once at the bottom, the water dissolves the salt and the oil floats back up.

The reason the oil doesn't dissolve into the water happens because of its difference in polarity. Water and salt are both polar. Oil is non-polar. Only polar substances will dissolve polar substances. A non-polar substance will not dissolve in a polar substance. This is the rule of "like dissolves like."

Tuesday, April 29, 2008

Testing week

Home Chemistry experiments are on hiatus this week for state-mandated standardized testing for the kids (and so Mom can catch up on writing deadlines). Posts will resume soon! In the meantime, a joke:

Q: Why are chemists great at solving problems?
A: They have all the solutions.
More chemistry jokes (and explanations) here.

Monday, April 21, 2008

Paper Mache and Gluten

Mixed up some flour paste for a paper mache project I'm going to be working on this week. According to The Papier Mache Resource, it's the gluten in the flour that makes it sticky. The Exploratorium has an animation that shows how the protein molecules line up to form a gooey elastic mess. My batch developed a sticky skin that I skimmed off -- hopefully the remaining liquid is goopy enough!

Description of image, borrowed from ChemConnections:

Molecular model of the spiral structure formed by the HMW subunits of glutenin.

Wednesday, April 16, 2008

Endothermic Reactions



As a continuation of our foray into heat-producing (exothermic) chemistry, we mixed up some solutions that became colder (endothermic). Endothermic reactions involve electrons jumping to higher orbitals, which requires an input of energy. The atoms absorb energy in the form of heat from the surrounding environment, thereby lowering the temperature. Unfortunately notetaking that day was not optimal, but here is an idea of what we did:

Since we didn't have the recommended styrofoam cups for mixing our solutions -- which I assume were supposed to provide some insulation between the solution and the air temperature around it -- we used doubled-up paper coffee cups (just like my favorite coffee shop). We used a meat thermometer I found around the house (purchased for a greenhouse gas experiment I never got around to doing) and a 99 cent house thermometer I picked up at Wal-Mart. All the experiments dropped a few degrees almost immediately, going from a water temperature of about 60 degrees Fahrenheit (sorry, we're working in an American kitchen, not a lab with metric measurements) to about 55 or 50 in a minute or so. You could just barely feel the difference by putting your finger in it (we totally forgot gloves and eye protection for this one), so the thermometer is a must.


First was potassium chloride, found in salt substitute. We mixed in an unmeasured proportion with tap water.


Next, we cut open a cold pack from an old first-aid kit. The cold-pack consisted of two compartments, one containing urea (or crystalized peepee, used in cigarettes, pretzels, bath oils, cloud seeding, and tooth whitening -- although I think they make it artificially!) and the other water. You're supposed to squeeze the water portion, which I guess forces it into the other portion. We just poured the crystals into a cup and added water.


The third mixture was baking soda and citric acid. We only had a small jar (scavenged from some old science kit, I believe) so we put about half a teaspoon in the cup and mixed with a little water. Then we poured in some baking soda. It fizzed up nicely, of course, as it would with vinegar. According to about.com, the reaction was:
H3C6H5O7(aq) + 3 NaHCO3(s) --> 3 CO2(g) + 3 H2O(l) + NaC6H5O7(aq)


Finally, we mixed some calcium chloride -- the kind of road salt used to melt icy sidewalks -- with water. Surprise! This one turned out to be exothermic. The temperature went up to 78 degrees. Pretty neat.

Monday, April 14, 2008

Your name in elements


Theodore Gray, creator of the lovely Periodic Table Table, emailed me today with news of his element banners. The idea is to spell words or phrases using only the one- or two-letter element abbreviations, then illustrate the spelling with photos from the poster of his table. The banners are pricey, but you can have fun just seeing how your name looks in elements. See a different version of my name here.

Crossposted to GeekDad.