Chemistry Archives - Page 2 of 6

Rosalind Franklin, a scientist whose role in the discovery of DNA structure in 1953 has been forgotten by many, has a chance to be immortalized in a feature film. Throughout her career she faced sexism at nearly every turn. She also happened to be Jewish, which heightened the prejudice against her. Her name may soon be on the tips of everyone’s tongue and her role in the discovery of DNA Structure known to all. Entertainment One has acquired the script to Exposure, her life story.

In 1962 James Watson, Francis Crick, and Maurice Wilkins jointly received the Nobel Prize in physiology or medicine for their 1953 determination of the structure of deoxyribonucleic acid (DNA). Rosalind Franklin (1920–1958), a colleague of Wilkins, died of cancer at the age of 37, and was thereby not equally honored because the Nobel Prize can only be shared by three scientists. It was her work in X-ray crystallography, however, that proved critical to the correct solution to DNA structure.

What is DNA?

DNA is the material embedded in the cells of all living organisms that carries the genetic coding that determines how a living thing will look and function. It is found in the nucleus of each cell and is unique to every individual – whether human, mountain lion, or butterfly. Its full name is deoxyribonucleic acid, which can be complicated to say, so we usually refer to it as DNA for short.

DNA is so tiny that it can not be seen unless we use a very powerful microscope. If we could see it we would see that it looks like a twisted ladder, which scientist refer to as the double helix. Each rung or step on the DNA ladder is composed of two letters.

There are only 4 letters — A,T,G, and C — and each has a unique puzzle-like shape. This means that A and T fit together to form a rung on the ladder and G and C fit together to form another rung on the ladder.

As we read the DNA ladder, the letters combine to form 3-letter words called codons. Then, these codons combine to form sentences that we call genes. These genes are the basis for your chromosomes, which give your body a blueprint or set of instructions for life.

Every human has 23 pairs of these DNA chromosomes that determine what we look like and how to perform. We get one set of chromosomes from our mother and one set from our father. Our chromosomes determine whether our eyes will be blue or brown, what color our skin and hair will be, whether we will be a boy or girl and so much more.

Building a Cardboard Safari DNA Double Helix Puzzle

Discovering DNA Structure

Inspired by Linus Pauling’s success in working with molecular models, James Watson and Francis Crick rapidly put together several models of DNA and attempted to incorporate all the evidence they could gather. Franklin’s excellent X-ray photographs, to which they had gained access without her permission, were critical to the correct solution. Along with Wilkins, Franklin’s partner, the four scientists announced the structure of DNA in articles that appeared together in the same issue of Nature.

After the publication, they moved on to different projects. Franklin went to Birkbeck College, London. Before her untimely death from cancer, she made important contributions to the X-ray crystallographic analysis of the structure of the tobacco mosaic virus, a landmark in the field. By the end of her life, she had become friends with Francis Crick and his wife and had moved her laboratory to Cambridge, where she undertook work on the poliovirus.

Biography

Rosalind Franklin was born July 25, 1920 to a Jewish family in London, England. Educated at private schools in London, she studied natural sciences at Newnham College, Cambridge, from where she graduated in 1941. She joined the University of Cambridge where she earned a research fellowship in a physical chemistry laboratory under Ronald George Wreyford Norrish. The British Coal Utilisation Research Association offered her a research position in 1942, and started her work on coals. This helped her earn a PhD in 1945.

In 1947, she went to Paris as a chercheur (post-doctoral researcher) under Jacques Mering at the Laboratoire Central des Services Chimiques de l’Etat, where she became an accomplished X-ray crystallographer. She returned to London in 1951 and became a research associate at King’s College. She was compelled to move to Birkbeck College after two years, however, owing to disagreeable clashes with her director and more so with her colleague Maurice Wilkins. At Birkbeck, J. D. Bernal, chair of the physics department, offered her a separate research team. She died on April 16, 1958 at the age of 37 of ovarian cancer.

Bring it Home

Build a model of the DNA Double Helix with the Cardboard Safari Puzzle

Create a model of DNA with colorful Wiki-Sticks

Extract DNA from Strawberries in this great lab from Marci at the Homeschool Scientist

Explore the DNA Teaching Resources from Karyn at Teach Beside Me

Challenge your students with this Transcription / Translation Lab Activity

Download the DNA & RNA Protein Synthesis Interactive Notebook Resources from Science with Amy

Make these cool DNA Sequence Bracelets

Watch this fabulous NOVA documentary on PBS, The Secret of Photo 51

You may also be interested in learning about other inventors and scientists who have made an impact in our lives.

The bloggers of the iHomeschool Network have teamed up to create fun and original unit studies on fascinating people who were born in July.

Have You Ever Wondered …

How does invisible ink work?

What common household substances can be used to make invisible ink?

What things can you do to reveal a message written in invisible ink?

Steganography is the practice of concealing a file, message, image, or video within another. The use of invisible inks is one of the earliest known examples of steganography. Invisible ink today is mostly considered child’s play, but in the not too distant past, its use and the recipes were considered classified government information.

Using the suggested inks and reagents provided here, write a secret message to a friend. Then get creative and see how many kinds of invisible ink you can find.

Types of Invisible Inks

There are two categories into which invisible inks fall ~ organic fluids and sympathetic inks. You can find many heat-activated invisible inks right inside your kitchen. Another type of invisible ink is chemically activated. Read on to learn more about each.

Organic or Heat-Activated Invisible Inks

Organic fluids consist of the natural methods your likely already familiar: lemon juice, vinegar, milk, or onion juice, to name a few. These organic invisible inks can be revealed through heat, such as with fire, irons, or light bulbs.

The organic fluids alter the fibers of the paper so that the secret writing has a lower burn temperature and turns brown faster than the surrounding paper when exposed to heat. To activate or develop the ink, simply iron the paper, set it on a radiator, place it in an oven (set lower than 450° F), or hold it up to a hot light bulb.

any acidic fruit juice (e.g., lemon, apple, or orange juice)
onion juice
sodium bicarbonate NaHCO₃solution (baking soda)
vinegar
white wine
diluted cola
milk
soapy water
sucrose solution (table sugar)
bodily fluids

A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute (baking soda or sugar) is a substance dissolved in another substance, known as a solvent (water).

Inquiry Science :: What other organic inks can you find? Which kind shows up best? Which kind lasts longest?

Sympathetic Inks

Sympathetic inks contain one or more chemicals and require the application of a specific “reagent” to be activated, such as another chemical or a mixture of chemicals. Most of these inks work using pH indicators, requiring the recipient to paint or spray a suspected message with a base (like sodium carbonate Na₂CO₃ or washing soda solution) or an acid (like lemon juice). Some of these inks will reveal their message when heated.

lemon juice, activated by iodine solution
starch (e.g., corn starch or potato starch), activated by iodine solution
vinegar or dilute acetic acid CH₃COOH, activated by red cabbage water
ammonia NH₃, activated by red cabbage water
sodium bicarbonate NaHCO3 (baking soda), activated by grape juice
sodium chloride NaCl (table salt), activated by silver nitrate
phenolphthalein (pH indicator), activated by ammonia fumes or sodium carbonate Na₂CO₃ (or another base)
lead nitrate, activated by sodium iodide
iron sulfate, activated by sodium carbonate, sodium sulfide, or potassium ferricyanide

CAUTION: Some of the chemicals suggested here can be hazardous if misused. Always use caution when working with chemicals. Read the information on the chemical label before you start, and always wear protective safety equipment such as goggles, gloves, and aprons. Adult supervision required.

Ultraviolet Light Activated Invisible Inks

Most of the inks that become visible when you shine an ultraviolet or black light on them will also become visible if you heat the paper. Here are are few ‘glow-in-the-dark’ ideas to try:

dilute laundry detergent (the bluing agent glows)
tonic water (quinine glows)
vitamin B-12 dissolved in vinegar

The History of Invisible Ink

The history of invisible ink is incredibly fascinating and swings wildly between high-tech methods and the humblest of approaches. Invisible ink was a key method for spy communications throughout history. Prisoners, Lovers, and Spies is an historical account of invisible ink and the secret communications revealed through thrilling stories about scoundrels, heroes, and their ingenious methods for concealing messages.

The Catholic Mary, Queen of Scots, kept under luxurious house arrest for eighteen years by her Protestant cousin Elizabeth I, advised correspondents to write to her employing two commonly used substances: alum (hydrated potassium aluminum sulfate) or nutgall (the tannic acid secreted in swellings generated by parasitic wasps colonizing oak trees). Letters written in alum required the recipient to soak the paper in water, while nutgall needed a solution of ferrous sulphate as a reagent.

During World War II, chemist Linus Pauling worked on an unusual wartime project, formulating new kinds of invisible ink that would resist all known reagents. Pauling and his colleagues experimented with invisible inks made from pneumococcus bacteria (an inert strain so as not to spread pneumonia). The ink-ified microbe would react to an antibody, and then become visible once dipped in a dye solution. However, the ink never passed the experimental stage.

Visit The Art of Manliness for a more detailed look at how invisible inks have been used in espionage and naval intelligence.

bio plastics Plastics play an important role in our lives. Plastics are used to manufacture many everyday items and have significantly reduced the use of glass. Some plastics are very durable and make things like furniture and appliances. Other plastics make items such as diapers, trash bags, cups, utensils and medical devices. The largest amount of plastic is used to make containers and packaging for items such as soft drink bottles, lids, shampoo bottles, etc. Common plastic is made from petroleum, a fossil fuel which is nonrenewable.

Nonrenewable resources are made naturally by the earth, but do not renew themselves fast enough to be able to count on having the resource for an indefinite period time. Some resources are considered non-renewable because our access to the resource is limited. For example, glass and metal are non-renewable resources. The elements and minerals used to make glass and metal are found in the structure of the earth’s crust, however we are limited to what we can access through mining.

Renewable resources are either naturally reproduced at a sustainable rate or they can be produced in agriculture at a rate equivalent to the demand or need. For example, corn can be used for ethanol fuel and to produce corn oil. Corn is a renewable resource.

Bioplastics are a type of plastic made from renewable, biological materials like starches, cellulose, oils or proteins. They generally contain little to no petroleum and therefore are usually biodegradable. When bioplastics are exposed to the environment (sunlight, heat, water, microorganisms) they breakdown into non-toxic compounds like carbon dioxide and water. Additionally, unlike petroleum-based plastics, bioplastics are made from renewable resources. These resources are typically agricultural byproducts, like cornstarch and potato starch, tapioca starch and casein (milk protein).

Biodegradable: refers to material capable of breaking down into harmless products through the action of living organisms or natural processes

Byproducts: in agriculture refers to secondary products created from a crop. For example, corn starch is a byproduct of corn

Make Your Own BioPlastics

Materials

Plant based oils (Corn Oil, Sesame Oil, Vegetable Oil)
Cornstarch
Water
Food coloring
Measuring spoons
Eyedropper (optional)
1 Ziploc bag per student
Access to a microwave oven

Procedure

Place the following ingredients in a plastic bag: 1 tablespoon of cornstarch, 2 drops of oil, 1 tablespoon of water, and 2 drops of food coloring.
Seal the bag and gently mix the cornstarch mixture by rubbing the outside of the bag with your fingers until combined.
Open the bag slightly, making sure it can vent. Place the bag in a microwave oven on high for 20-25 seconds.
Carefully remove the bag from the microwave and let it cool for a few minutes. While it is still warm, students can try to form their plastic into a ball. Observe what it does.
Ask them to describe their plastic; did it turn out differently than others? Does the type of oil you used affect the bioplastic? Have the students name three things they could make with bioplastic.

Take it Further

I’m committed to sharing activities and resources for teaching science in your homeschool. I believe it is helpful to see that science isn’t scary and it doesn’t require special curriculum. Here are a few resources that you can use to further your study of plastics and renewable vs. nonrenewable resources.

Watch the 3-minute How Stuff Works video clip about Corn Plastic.

In this hands-on, inquiry based Plastics Lab Activity, students investigate whether all plastics the same? How are they different?

Polymers Are Cool ~ Experiment with different polymers, large molecules composed of many repeated subunits, with these 3 great recipes.

As plastics are not biodegradable, learn how you can make a difference in encouraging others to reduce our use of plastics. The volunteers at Washed Ashore inspired us to create a Bottle Cap Mural to help spread the word of the harm done to our oceans by plastics.

Chemistry is great for making many useful products. It’s also good for making stuff that’s just fun to play with. One of my favorite chemistry units is on polymers.

A polymer is a large molecule, or macromolecule, composed of many repeated subunits. In other words, they are made up of many, many molecules all strung together to form really long chains.

In Greek, Poly- means “many” and -mer means “part” or “segment”. Mono means “one”. So, monomers are the individual molecules that can join together to make a long polymer chain.

A single polymer molecule is made out of hundreds of thousands (or even millions!) of monomers. Not all molecules can link up in this way to form polymers, however.

The atoms that make up a polymer chain essentially line up and repeat all along the length of the polymer chain. For example, look at polypropylene:

Polypropylene is made up of just two carbon atoms repeated over and over again. One carbon atom has two hydrogen atoms attached to it, and the other carbon atom has one hydrogen atom and one pendant methyl group (CH₃).

In this example, the pendant group hangs from the carbon atom in the chain backbone. As you can see from the example, pendant groups usually repeat along the length of the chain as well.

But enough of the mumbo jumbo. Let’s get to the fun stuff. What is better than reading about chemistry? Doing the labs, of course! Here are three tried and true recipes for polymers you can use in the classroom.

Polymer Recipes ~ Get Messy!

Basic Polymer Putty

This is a fun and easy polymer to make (and the one featured in the photographs).

Materials

Elmer’s white glue
Borax (find in the laundry detergent aisle of the store)
Water
Two bowls
Food coloring (just for fun)

Procedure

In one bowl mix 1/2 cup (4 oz) glue and 1/2 cup water. Add food coloring if you want colored slime.
In the other bowl, slowly mix borax into 1 cup of water until the borax will no longer dissolve (this is a saturated solution).
Add the glue mixture to the borax solution, stirring slowly.
The slime will begin to form immediately; stir as much as you can, then dig in and knead it with your hands until it gets less sticky. Don’t worry about any leftover water in the bowl; just pour it out.

The glue has an ingredient called polyvinyl acetate, which is a liquid polymer. The borax links the polyvinyl acetate molecules to each other, creating one large, flexible polymer. It will get stiffer and more like putty the more you play with it.

Store it in a plastic bag in the fridge, to keep it from growing mold.

A Firmer Polymer

This recipe makes a firmer, dryer slime that will even bounce if it is kneaded enough.

Mix 4 tsp. (20 ml) water with 5 tsp. (25 ml) Elmer’s or other white glue in a small bowl.
Add 1 tsp. (5 ml) talcum powder and stir until thoroughly mixed.
Add 1 or 2 tsp. (5 or 10 ml) saturated borax and water solution. Stir four a few minutes.
Remove the glob from the bowl and stirrer. Knead it for a while and it will become drier.

You will probably need to wipe off some of the excess moisture from your hands with a paper towel from time to time. Don’t be tempted to wipe the glob with a paper towel as it will only stick. You can add a little talcum to the surface if you are having trouble getting it dry enough. Store in a zip lock in the fridge.

Take a closer look at plastics & polymers

Super Slime

This slime is similar to the one above, but creates a less rubbery and more transparent slime. This is the real gooey deal! (This slime is non-toxic, but still keep these chemicals away from unsupervised children and wash your hands after playing with the slime.)

Materials

Polyvinyl Alcohol (PVA)
Borax
Water
Graduated cylinder or measuring cups and spoons
Food coloring (just for fun)

Procedure

Make a 4% solution of polyvinyl alcohol: Stir 1.5 teaspoons (approx. 4g) of PVA into 1/2 C (approx 100 ml) of water in a large microwave-safe bowl. Cover the bowl and microwave for 1 minute, then stir. Microwave another 30 seconds and stir. Continue until all the PVA is dissolved. A slight film may have formed on top; you can remove that with a spoon. You can add food coloring if you want colored slime. Allow the solution to cool.
Make a 4% borax solution by stirring a little less than 2 teaspoons (approx. 4g) of Borax into 1/2 cup of water.
Pour the cooled PVA solution into a ziplock bag and add 2 teaspoons (10ml) of the borax solution.
Zip the bag and knead it until the chemicals are mixed into slime. Then scoop it out and play with it.

While water is a liquid made up of individual H2O molecules, polyvinyl alcohol is formed of long chains of connected molecules, making it a liquid polymer. The borax acts as a “cross-linker,” linking the individual PVA chains to each other. The borax molecules form hydrogen bonds with molecules present in the PVA chains. The partial positive charge of hydrogen atoms attracts the partial negative charge of oxygen atoms. Since hydrogen bonds are weak, they can break and reform as you play with the slime or let it ooze on a flat surface.

Your slime will last for a while if you seal it in a plastic bag and keep it in the fridge.

Learn how to dispel children’s Misconceptions in Chemistry & Physics.

Helpful Hints for Success with Polymers

Gel type glues

Over the past few years several brands of gel type glues have been introduced. Most of these make excellent slimes which are very elastic and have a nice color and consistency. I have personally experimented with Elmer’s School Glue Gel, but there are several similar products available from other manufacturers. Try substituting a gel glue in the Basic Polymer recipe, above.

Slime overly sticky or runny?

If your white glue or gel glue based slime is too sticky or runny, first try kneading it for a while. Working it in your hands will help to mix things up better, as well as remove some of the moisture. If it is still not quite right, mix 1 part borax with 10 parts water. Dunk the slime into this solution, remove and knead.

Precautions

Polymers can wreak havoc with plumbing, so don’t throw them down the drain.
Always wear a mask when mixing PVA.
Use distilled water for all solutions for best results.
Keep polymers away from anything they could damage. They can dry into fabric and the dyes can stain surfaces, including wood.
Supervise small children when playing with polymers so they do not ingest any.
Some people are allergic to Borax powder. Wearing rubber gloves when mixing should help.
Polymers using Borax solutions work best if you pour the Borax solution into the other solution, rather than the other way around. Coloring should be added before the Borax.
Use metric measurements whenever possible. This will make it simpler to experiment with different concentrations and ratios.

For more hands-on chemistry lessons like this one, check out Cool Chemistry is a ten-week multidisciplinary, hands-on physical science curriculum that incorporates scientific inquiry and a long-term project. Available today!

For the past six years or so, we have purchased our dairy products direct from a local farmer. My kids and I love the taste of raw milk and crave its distinctive flavor. We can even taste the difference between farm fresh eggs from chickens allowed to wander and graze on a variety of foods (including insects and other invertebrates) and eggs from chickens confined to a small cage their entire lives.

We first tried raw milk at the home of a homeschool family in Bend, Oregon. It was deliciously creamy. We soon heard stories of friends who had experienced amazing results — ear infections, asthma, and allergies — all diminished after changing to a diet of Real And Wholesome milk. Thus began our journey towards a more wholesome diet – including raw milk.

Raw milk is milk from cows, sheep, or goats that has not been pasteurized. Pasteurization is a process that kills harmful bacteria by heating milk to a specific temperature for a set period of time. First developed by Louis Pasteur in 1864, pasteurization kills harmful organisms responsible for such diseases as listeriosis, typhoid fever, tuberculosis, diphtheria, and brucellosis.

Controversial, proponents on both sides of the pasteurization debate will cite research and anecdotal evidence to support their side. Did you know, however, that Pasteur initially developed the process for which he is most well known not for milk but for wine? As he was born in December, I thought I would share a little insight into the life and the impact of Louis Pasteur.

Biography

Born on December 27, 1822, in Dole, France, Louis Pasteur was the son of a sergeant major in the Napoleonic wars who grew up in Arbois, a small town in eastern France surrounded by farms and vineyards.

“When I approach a child, he inspires in me two sentiments; tenderness for what he is, and respect for what he may become.” ~ Louis Pasteur

An average student, Pasteur had a passion for drawing and painting. As a boy, he captured his family in a series of lifelike portraits, Pasteur: Dessins et pastels, which showed a keen eye for precision and detail. While his teachers encouraged his artistic side, his father considered painting an indulgence: what counted was solid schoolwork.

Pasteur began a career in chemistry with a post at the University of Strasbourg and quickly made a ground-breaking discovery. He showed that otherwise identical molecules could exist as mirror images (or ‘left’ and ‘right-handed’ versions). He noticed that molecules produced by living things were always left-handed. This discovery was a fundamental step forward in microbiology, underpinning modern drug development and even our understanding of DNA.

Pasteur also disproved the age-old theory that life appeared spontaneously with a simple experiment. He showed that food decayed because of contamination by microbes in the air. He went on to argue that these could cause disease. Though his ‘germ theory’ was initially controversial (he was not a doctor, after all), it eventually led to the development of antiseptics and changed healthcare forever.

“A bottle of wine contains more philosophy than all the books in the world.” ~ Louis Pasteur

Relatedly, he discovered that microbes were responsible for souring alcohol. In a series of careful experiments, Pasteur discovered that heating wine to 55 degrees killed bacteria without ruining the taste. This process, later named pasteurization, saved the wine industry, and cemented Pasteur’s fame. Today, this process is widely used to keep food free from disease.

“Officially, I recommend the pasteurization of milk. But I still love drinking it straight from the udder.” ~ Louis Pasteur

While Louis Pasteur is most well known for developing the process of pasteurization; his work in germ theory also led him to create vaccinations for rabies, a highly contagious infection which attacks the central nervous system. It enters the body through the bite of an infected animal or through infected saliva entering an existing wound.

After experimenting with the saliva of animals suffering from the disease, Pasteur concluded that the disease rests in the central nervous system of the body. When an extract from the spinal column of an rabid dog was injected into healthy animals symptoms of rabies were produced. By studying the tissues of infected animals – rabbits, Pasteur was able to produce an attenuated form of the virus that could be used for inoculation.

Pasteur became a national hero and was honored in many ways. He died at Saint-Cloud on 28 September 1895 and was given a state funeral at the Cathedral of Notre Dame and his body placed in a permanent crypt at the Pasteur Institute.

Bring it Home

➤ In the lab, Milk – How Sweet Is It?, students test different samples to see which ones contain the lactase enzyme.

➤ The enzyme lactase is produced in the small intestines of infants where it breaks down the sugar lactose found in milk. Zoom in to the molecular level to see how the enzyme works in this striking animation, Lactose Digestion in Infants.

➤ Learn how a single genetic mutation that first enabled ancient Europeans to drink milk, The Milk Revolution.

➤ Check out the The Science of Milk TED-Ed lesson by Jonathan O’Sullivan

➤ After watching the short film Got Lactase?, students may explore how the enzyme lactase hydrolyzes lactose into monosaccharides, and practice graphing and analyzing data. The accompanying worksheet requires them to provide reasoning for their answers. If you have time to explore the extension portion of the activity, you can tie in anaerobic respiration and why lactase non-persistence causes pain and discomfort. (Recommend for high school level)

Whenever I teach introductory chemistry, one of my favorite activities is to create rock candy. Rock candy is formed by allowing a supersaturated solution of sugar and water to crystallize onto a surface suitable for crystal nucleation, such as a string or stick.

STEM Club kids were delighted the day I told them we were making rock candy in class. Sadly, our “experiment” didn’t turn out as expected.

Words to Know

Mixture :: A mixture is simply a combination of two or more substances that do not react to form something new. For example, mud, cake batter, milk, salad, latex paint, black top (asphalt and gravel). Mixtures are combinations of compounds that can be separated by mechanical or physical processes. If the atoms can only be separated with chemical reactions, they are complex molecules, not mixtures.

Solution :: A special kind of mixture called a solution is where mixing occurs at the molecular level. Examples are sea water, Kool-Aid, antifreeze, seltzer water, and gasoline.

In a solution, one or more substances are dissolved into another substance. In the example of Kool-Aid, the sugar and mix are dissolved into water. The substance that gets dissolved is referred to as the solute. The substance that dissolves a solute is referred to as the solvent. A solvent is usually a liquid but can also be a solid or a gas. In this example, Kool-Aid is the solute and water is the solvent.

All solutions are mixtures, but not all mixtures are solutions. Solutions are homogeneous mixtures (uniform in composition or character).

Saturated Solution :: A saturated solution is one in which no more solute can be dissolved.

Supersaturated Solution :: The physical properties of a compound can change when other substances or compounds are added. The melting or boiling point can increase or in some cases decrease. Raising the temperature of a compound (water for example) will enable you to dissolve more sugar into the solution. This creates a super-saturated solution.

How to Make Rock Candy

Materials

2 cups water
4 cups granulated sugar
1/2-1 tsp flavoring extract or oil (optional)
food coloring (optional)
glass jar
wooden skewer and a clothespin

Procedure

1. Wash a glass jar thoroughly with hot water to clean it. Wet the skewer, and roll it in granulated sugar. This base layer will give the sugar crystals something to “grab” when they start forming. Set the skewer aside to dry while you prepare your sugar syrup.

2. Place the water in a medium-sized pan and bring it to a boil. Begin adding the sugar, one cup at a time, stirring after each addition. Heating the water before adding the sugar allows more sugar to dissolve thus producing larger crystals.

You will notice that it takes longer for the sugar to dissolve after each addition. Continue to stir and boil the syrup until all of the sugar has been added and it is all dissolved. Remove the pan from the heat.

3. If you are using colors or flavorings, add them at this point. If you are using an extract, add 1 tsp of extract, but if you are using flavoring oils, only add ½ tsp. Add 2-3 drops of food coloring and stir to ensure even, smooth color.

4. Allow the sugar syrup to cool for approximately 10 minutes, then pour it into the prepared jar. Suspend the skewer into the solution about 1 inch from the bottom.

5. Carefully place your jar in a cool place, away from harsh lights, where it can sit undisturbed. Cover the top loosely with plastic wrap or paper towel.

7. You should start to see sugar crystals forming within 2-4 hours. If you have seen no change to your skewer or thread after 24 hours, try boiling the sugar syrup again and dissolve another cup of sugar into it, then pour it back into the jar and insert the string or skewer again.

8. Allow the rock candy to grow until it is the size you want. Once it has reached the size you want, remove it and allow it to dry for a few minutes, then enjoy or wrap in plastic wrap to save it for later.

Our Results & What We Learned

As we were underway, my thought was, “I don’t want a dozen jars of sticky sugar syrup on my counter for the next week or so. We may as well put all the skewers into the same jar – one for every student.”

I clearly didn’t think this through. As the water evaporated, the crystals grew and expanded. Eventually, they merged and even began to grow onto the sides of the jar. I was unable to remove the skewers and a few even broke off from the tension as I tried to pull them out.

I tried using a knife to break apart the crystals. I even placed the jar into a water bath in an attempt to reheat the solution and melt the crystals. Can you guess what happened?

Yep! The jar broke!! Even though it was a pressurized Kerr canning jar. Yikes!

We thereby learned it is best to suspend a single skewer into a glass of sugar solution to avoid crystal conglomeration. Keep an eye on the progress – don’t let it grow too large. You don’t want the crystals to reach the bottom or you’ll have difficulty removing the skewer.

Cultural Notes

Rock candy is a common ingredient in Chinese cooking, and many households have rock candy available to marinate meats and add to stir fry. It is used to sweeten Chrysanthemum tea and Cantonese dessert soups. It is also an important part of the tea culture of East Frisia and Tamil cuisine in India.

If you enjoyed this activity and would like to expand on the concepts introduced here, I encourage you to check out my 10-weekmultidisciplinary, hands-on chemistry curriculum, Physics Logic: Cool Chemistry.

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