How to Grow Great Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Tip, Tricks, and Techniques Do you want to grow great crystals? These are general instructions for growing crystals that you can use for most crystal recipes. You can find the recipes and information on crystal structures in the Growing Crystals section. Here are the basics, to get you started and help you troubleshoot problems: What Are Crystals? Crystals are structures that are formed from a regular repeated pattern of connected atoms or molecules. Crystals grow by a process termed nucleation. During nucleation, the atoms or molecules that will crystallize (solute) are dissolved into their individual units in a solvent. The solute particles contact each other and connect with each other. This subunit is larger than an individual particle, so more particles will contact and connect with it. Eventually, this crystal nucleus becomes large enough that it falls out of solution (crystallizes). Other solute molecules will continue to attach to the surface of the crystal, causing it to grow until a balance or equilibrium is reached between the solute molecules in the crystal and those that remain in the solution. The Basic Technique Make a saturated solution. Start a garden or grow a seed crystal. Continue growth. In order to grow a crystal, you need to make a solution which maximizes the chances for the solute particles to come together and form a nucleus, which will grow into your crystal. This means you will want a concentrated solution with as much solute as you can dissolve (saturated solution). Sometimes nucleation can occur simply through the interactions between the solute particles in the solution (called unassisted nucleation), but sometimes it's better to provided a sort of meeting place for solute particles to aggregate (assisted nucleation). A rough surface tends to be more attractive for nucleation than a smooth surface. As an example, a crystal is more likely to start forming on a rough piece of string than on the smooth side of a glass. Make a Saturated Solution It's best to start your crystals with a saturated solution. A more dilute solution will become saturated as the air evaporates some liquid, but evaporation takes time (days, weeks). You will get your crystals more quickly if the solution is saturated to begin with. Also, there may come a time when you need to add more liquid to your crystal solution. If your solution is anything but saturated, then it will undo your work and actually dissolve your crystals! Make a saturated solution by adding your crystal solute (e.g., alum, sugar, salt) to the solvent (usually water, although some recipes may call for other solvents). Stirring the mix will help to dissolve the solute. Sometimes you may want to apply heat to help the solute dissolve. You can use boiling water or sometimes even heat the solution on the stove, over a burner, or in a microwave. Growing a Crystal Garden or 'Geode' If you just want to grow a mass of crystals or a crystal garden, you can pour your saturated solution over a substrate (rocks, brick, sponge), cover the setup with a paper towel or coffee filter to keep out dust, and allow the liquid to slowly evaporate. Growing a Seed Crystal On the other hand, if you are trying to grow a larger single crystal, you will need to obtain a seed crystal. One method of getting a seed crystal is to pour a small amount of your saturated solution onto a plate, let the drop evaporate, and scrape the crystals formed on the bottom to use as seeds. Another method is to pour saturated solution into a very smooth container (like a glass jar) and dangle a rough object (like a piece of string) into the liquid. Small crystals will start to grow on the string, which can be used as seed crystals. Crystal Growth and Housekeeping If your seed crystal is on a string, pour the liquid into a clean container (otherwise crystals will eventually grow on the glass and compete with your crystal), suspend the string in the liquid, cover the container with a paper towel or coffee filter (don't seal it with a lid!), and continue to grow your crystal. Pour the liquid into a clean container whenever you see crystals growing on the container. If you selected a seed from a plate, tie it onto a nylon fishing line (too smooth to be attractive to crystals, so your seed can grow without competition), suspend the crystal in a clean container with saturated solution, and grow your crystal the same way as with seeds that were originally on a string. Keeping Your Treasures Crystals that were made from a water (aqueous) solution will dissolve somewhat in humid air. Keep your crystal beautiful by storing it in a dry, closed container. You may wish to wrap it in paper to keep it dry and prevent dust from accumulating on it. Certain crystals can be protected by being sealed with an acrylic coating (like Future floor polish), although applying the acrylic will dissolve the outermost layer of the crystal. Types of Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Shapes and Structures There's more than one way to categorize a crystal! The two most common methods are to group them according to their crystalline structure and to to group them according to their chemical/physical properties: Crystal Grouped by Lattices (Shape) There are seven crystal lattice systems. You can view examples of each type by following one of the 'Elsewhere on the Web' links I have provided. 1. Cubic or Isometric - not always cube shaped! You'll also find octahedrons (eight faces) and dodecahedrons (10 faces). 2. Tetragonal - similar to cubic crystals, but longer along one axis than the other, forming double pyramids and prisms. 3. Orthorhombic - like tetragonal crystals except not square in cross section (when viewing the crystal on end), forming rhombic prisms or dipyramids (two pyramids stuck together). 4. Hexagonal - six-sided prisms. When you look at the crystal on-end, the cross section is a hexagon. 5. Trigonal - possess a single 3-fold axis of rotation instead of the 6-fold axis of the hexagonal division. 6. Triclinic - usually not symmetrical from one side to the other, which can lead to some fairly strange shapes. 7. Monoclinic - like skewed tetragonal crystals, often forming prisms and double pyramids. This is a very simplified view of crystal structures. In addition, the lattices can be primitive (only one lattice point per unit cell) or non-primitive (more than one lattice point per unit cell). Combining the 7 crystal systems with the 2 lattice types yields the 14 Bravais Lattices (named after Auguste Bravais, who worked out lattice structures in 1850). The structure of real crystals is pretty complicated! You can read about crystallography and mineral structures here and here. Crystals Grouped by Properties There are four main categories of crystals, as grouped by their chemical and physical properties: 1. Covalent Crystals A covalent crystals has true covalent bonds between all of the atoms in the crystal. You can think of a covalent crystal as one big molecule. Many covalent crystals have extremely high melting points. Examples of covalent crystals include diamond and zinc sulfide crystals. 2. Metallic Crystals Individual metal atoms of metallic crystals sit on lattice sites. This leaves the outer electrons of these atoms free to float around the lattice. Metallic crystals tend to be very dense and have high melting points. 3. Ionic Crystals The atoms of ionic crystals are held together by electrostatic forces (ionic bonds). Ionic crystals are hard and have relatively high melting points. Table salt (NaCl) is an example of this type of crystal. 4. Molecular Crystals These crystals contain recognizable molecules within their structures. A molecular crystal is held together by non-covalent interactions, like van der Waals forces or hydrogen bonding. Molecular crystals tend to be soft with relatively low melting points. Rock candy, the crystalline form of table sugar or sucrose, is an example of a molecular crystal. As with the lattice classification system, this system isn't completely cut-and-dried. Sometimes it's hard to categorize crystals as belonging to one class as opposed to another. However, these broad groupings will provide you with some understanding of structures. I'll test your knowledge by referring to these crystal shapes in crystal-growing tutorials! Crystal Growing - Troubleshooting Problems From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Find Out What Went Wrong There may come a time when you will try to grow a crystal without success. Here are some ideas for possible problems and ways to correct them: No crystal growth This is usually caused by using a solution that isn't saturated. The cure is to dissolve more solute into the liquid. Stirring and applying heat can help to get solute into solution. Keep adding solute until you start to see some accumulate at the bottom of your container. Let it settle out of solution, then pour or siphon the solution off, being careful not to pick up undissolved solute. If you don't have any more solute to use, you can take some comfort in knowing that the solution will become more concentrated over time, as evaporation removes some of the solvent. You can speed this process by increasing the temperature where your crystals are growing or by increasing air circulation. Remember, your solution should be loosely covered with a cloth or paper to prevent contamination, not sealed. If you are sure your solution is saturated, try to eliminate these other common reasons for lack of crystal growth: o Too much vibration Keep your crystal setup in a quiet, undisturbed location. o Contaminant in the solution The fix is to re-make your solution. The fix only works if you can avoid contamination (won't work if your starting solute is the problem). Common contaminants include oxides from paper clips or pipe cleaners (if you're using them), detergent residue on the container, dust or something else falling into the container. o Inappropriate temperature Experiment with temperature. You may need to increase the temperature around your crystals to get them to grow (increases evaporation). For some crystals, you may need to decrease the temperature (which slows the molecules down and gives them a change to bind together). o Solution cooled too quickly or slowly Did you heat your solution to saturate it? Should you heat it? Should you cool it? Experiment with this variable. If the temperature changed from the time you made the solution to the present time, the rate of cooling may make a difference. You can increase the rate of cooling by putting the fresh solution in a refrigerator or freezer (faster) or leaving it on a warm stove or in an insulated container (slower). If the temperature didn't change, maybe it should (heat the initial solution). o Water wasn't pure If you used tap water, try re-making the solution using distilled water. If you have access to a chemistry lab, try deionized water that was purified by distillation or reverse osmosis. Remember... water is only as clean as its container! The same rules apply to other solvents. o Too much light An unlikely problem with home crystals, but for certain materials the energy from light can inhibit the formation of chemical bonds. No seed crystals If you are trying to grow a large single crystal, you will need to get a seed crystal first. For some substances, the seed crystals may form spontaneously on the side of the container. For others, you may need to pour a small amount onto a saucer and let it evaporate to get crystals. Sometimes crystals will grow best on a rough string suspended into the liquid. The composition of the string is important! You are more likely to get crystal growth on cotton or wool string than on nylon or a fluoropolymer. Seed crystals dissolve when placed in new container This happens when the solution isn't fully saturated. See above for details. How To Grow a Big Alum Crystal From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Alum is found in the 'spices' section of the grocery store. With a bit of time and effort, you can grow a big alum crystal. Difficulty: Easy Time Required: Days to Weeks Here's How: 1. Pour 1/2 cup of hot tap water into a clean jar. 2. Slowly stir in alum, a little at a time, until it stops dissolving. Don't add the whole amount - just enough to saturate the water. 3. Loosely cover the jar with a coffee filter or paper towel (to keep dust out) and allow the jar to sit undisturbed overnight. 4. The next day, pour the alum solution from the first jar into the clean jar. You will see small alum crystals at the bottom of the jar. These are 'seed' crystals that you will use to grow a big crystal. 5. Tie nylon fishing line around the largest, best-shaped crystal. Tie the other end to a flat object (e.g., popsicle stick, ruler, pencil, butter knife). You will hang the seed crystal by this flat object into the jar far enough so that it will be covered in liquid, but won't touch the bottom or sides of the jar. It may take a few tries to get the length just right. 6. When you have the right string length, hang the seed crystal in the jar with the alum solution. Cover it with the coffee filter and grow a crystal! 7. Grow your crystal until you are satisfied with it. If you see crystals starting to grow on the sides or bottom of your jar, carefully remove your crystal, pour the liquid into the clean jar, and put the crystal in the new jar. Other crystals in the jar will compete with your crystal for alum, so it won't be able to get as big if you let these crystals grow. Tips: 1. You can use sewing thread or other string instead of nylon fishing line, but crystals will grow on the entire length of the submerged string. Crystals don't adhere to nylon, so if you use it, you can get bigger, better crystals. 2. Alum is an ingredient used to make pickles. It makes them crispy. What You Need: 1/2 c hot tap water 2 clean jars 2-1/2 T alum spoon nylon fishing line coffee filter/paper towel pencil, ruler, or knife More How To's from your Guide To Chemistry http://chemistry.about.com/cs/ht.htm How To Grow Borax Crystal From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Do real snowflakes melt too quickly? Grow a borax snowflake, color it blue if you like, and enjoy the sparkle all year long! Difficulty: Average Time Required: Overnight Here's How: 1. Cut a pipe cleaner into any various lengths to create a shape you desire 2. Twist the sections together at their centers to form a shape. Don't worry if an end isn't even, just trim to get the desired shape. The shape should fit inside the jar. 3. Tie the string to the end of your shape. Tie the other end of the string to the pencil. You want the length to be such that the pencil hangs the shape into the jar. 4. Fill the wide mouth pint jar with boiling water. 5. Add borax one tablespoon at a time to the boiling water, stirring to dissolve after each addition. The amount used is 3 tablespoons borax per cup of water. It is okay if some undissolved borax settles to the bottom of the jar. 6. If desired, you may tint the mixture with food color. 7. Hang the pipe cleaner shape into the jar so that the pencil rests on top of the jar and the snowflake is completely covered with liquid and hangs freely (not touching the bottom of the jar). 8. Allow the jar to sit in an undisturbed location overnight. 9. Look at the pretty crystals!!! You can hang your shape as a decoration or in a window to catch the sunlight :-) Tips: 1. Borax is available at grocery stores 2. res in the laundry soap section, such as 20 Mule Team Borax Laundry Booster. Do not use Boraxo soap. 3. Because boiling water is used and because borax isn't intended for eating, adult supervision is recommended for this project. 4. If you can't find borax, you can use sugar or salt (may take longer to grow the crystals, so be patient). Add sugar or salt to the boiling water until it stops dissolving. Ideally you want no crystals at the bottom of the jar. What You Need: string pencil wide mouth jar (pint) boiling water pipe cleaners blue food coloring (opt.) borax (see tips) scissors How To Grow a Bluing Crystal Garden From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Make delicate, colorful crystals! This is a great classic crystal-growing project. You use porous materials (i.e.charcol, sponges, rough rocks, brick, filter paper, etc), ammonia, salt, bluing, and food coloring to grow a sort of crystal garden. The components of the garden are toxic, so adult supervision is recommended. Be sure to keep your growing garden away from young children and pets! Difficulty: Easy Time Required: 2 days to 2 weeks Here's How: 1. Place chunks of your substrate (i.e., charcoal briquette, sponge, cork, brick, porous rock) in an even layer in the non-metal pan. You want pieces that are roughly 1-inch in diameter, so you may need to (carefully) use a hammer to break the material up. 2. Sprinkle water, preferably distilled, onto the substrate until is has been thoroughly dampened. Pour off any excess water. 3. In an empty jar, mix 3 tablespoons (45 ml) uniodized salt, 3 tablespoons (45 ml) ammonia, and 6 tablespoons (90 ml) bluing. Stir until the salt is dissolved. 4. Pour the mixture over the prepared substrate. 5. Add and swirl a bit of water around in the empty jar to pick up the remaining chemicals and pour this liquid onto the substrate, too. 6. Add a drop of food coloring here and there across the surface of the 'garden'. Areas with no food coloring will be white. 7. Sprinkle more salt (about 2 T or about 30 ml) across the surface of the 'garden'. 8. Set the 'garden' in an area where it will not be disturbed. 9. On days 2 and 3, pour a mixture of ammonia, water, and bluing (2 tablespoons or 30 ml each) in the bottom of the pan, being careful not to disturb the delicate growing crystals. 10. Keep the pan in an undisturbed place, but check on it periodically to watch your very cool garden grow! Tips: 1. If you can't find bluing at a store near you, it is available online: http://www.mrsstewart.com/ (Mrs. Stewart's Bluing). 2. Crystals form on the porous materials and grow by drawing up the solution using capillary action. Water evaporates on the surface, depositing solids/forming crystals, and pulling more solution up from the base of the pie plate. What You Need: Charcoal Briquettes (or pieces of Food Coloring sponge or brick or porous rock) Non-Metal Pie Plate (glass is Distilled Water great) Uniodized Salt Measuring Spoons Ammonia Empty Jar Bluing How To Grow Sugar Crystals - Make Your Own Rock Candy From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. It's easy to grow your own sugar crystals! Sugar crystals are also known as rock candy since the crystallized sucrose (table sugar) resembles rock crystals and because you can eat your finished product. You can grow beautiful clear sugar crystals with sugar and water or you can add food coloring to get colored crystals. It's simple, safe, and fun. Boiling water is required to dissolve the sugar, so adult supervision is recommended for this project. Difficulty: Easy Time Required: a few days to a week Here's How: 1. Gather your materials. 2. You may wish to grow a seed crystal, a small crystal to weight your string and provide a surface for larger crystals to grow onto. A seed crystal is not necessary as long as you are using a rough string or yarn. 3. Tie the string to a pencil or butter knife. If you have made a seed crystal, tie it to the bottom of the string. Set the pencil or knife across the top of the glass jar and make sure that the string will hang into the jar without touching its sides or bottom. However, you want the string to hang nearly to the bottom. Adjust the length of the string, if necessary. 4. Boil the water. If you boil your water in the microwave, be very careful removing it to avoid getting splashed! 5. Stir in the sugar, a teaspoonful at a time. Keep adding sugar until it starts to accumulate at the bottom of the container and won't dissolve even with more stirring. This means your sugar solution is saturated. If you don't use a saturated solution, then your crystals won't grow quickly. On the other hand, if you add too much sugar, new crystals will grow on the undissolved sugar and not on your string. 6. If you want colored crystals, stir in a few drops of food coloring. 7. Pour your solution into the clear glass jar. If you have undissolved sugar at the bottom of your container, avoid getting it in the jar. 8. Place the pencil over the jar and allow the string to dangle into the liquid. 9. Set the jar somewhere where it can remain undisturbed. If you like, you can set a coffee filter or paper towel over the jar to prevent dust from falling into the jar. 10. Check on your crystals after a day. You should be able to see the beginnings of crystal growth on the string or seed crystal. 11. Let the crystals grow until they have reached the desired size or have stopped growing. At this point, you can pull out the string and allow the crystal to dry. You can eat them or keep them. Have fun! Tips: 1. Crystals will form on a cotton or wool string or yarn, but not on a nylon line. If you use a nylon line, tie a seed crystal to it to stimulate crystal growth. 2. If you are making the crystals to eat, please don't use a fishing weight to hold your string down. The lead from the weight will end up in the water -- it's toxic. Paper clips are a better choice, but still not great. What You Need: 1 cup water 3 cups table sugar (sucrose) clean glass jar pencil or butter knife string pan or bowl for boiling water and making solution spoon or stirring rod More How To's from your Guide To Chemistry http://chemistry.about.com/cs/ht.htm How To Grow Crystal Spikes in the Sun From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Most crystals take days or weeks to form. Use this technique if you have a sunny day and want crystals FAST! Difficulty: Easy Time Required: 1-3 hours Here's How: 1. First, a sunny day isn't required, but it will help! You want rapid evaporation of the water to form the crystals, so select a warm, dry place to grow crystals (sunny porch or window is great). 2. Use the scissors to cut black (or other dark color) construction paper so that it will fit in the bottom of the pan. 3. Add 1 tablespoon of Epsom salt to 1/4 cup warm water. Stir until the salt is dissolved. 4. Put the construction paper in the pan and pour the salt solution over the paper. 5. Put the pan in the place you have selected for crystal-growing. As the water evaporates, you'll see lots of spiky crystals. 6. Have fun! Use a magnifying glass to see your creations up-close. Tips: 1. This is one of the fastest, least toxic methods of growing crystals. You can substitute regular salt for Epsom, but the resulting crystals won't be as exciting. 2. Wash your hands after handling Epsom salts. Don't drink the solution and avoid spilling it on yourself. 3. Experiment with adding water colors or food color to the salt solution. What You Need: black construction paper pie or cake pan warm water Epsom salt scissors More How To's from your Guide To Chemistry http://chemistry.about.com/cs/ht.htm How To Grow Epsom Salt (Magnesium Sulfate) Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. You can find epsom salts (magnesium sulfate) in the laundry and pharmacy sections of most stores. Epsom salt crystals are safe to handle, easy to grow, and form quickly. You can grow clear crystals or add food coloring if you prefer. Here's what you need to know to make your own crystals. Difficulty: Easy Time Required: A Few Days Here's How: 1. Boil the water in a microwave or on the stove. 2. Remove the water from heat and add the epsom salts. Stir the mixture until the salt is fully dissolved. If desired, add food coloring. 3. Pour the mixture over a piece of sponge (optional) or into a shallow container. You need just enough liquid to cover the bottom of the container. 4. Place the container in a warm or sunny location. Crystals will form as the water evaporates. Tips: 1. The sponge provides extra surface area to allow the crystals to form more quickly and helps make them a bit easier to view and handle. 2. Compare the appearance of the epsom salts before stirring them into the water with the appearance of the crystals that are produced. What You Need: 1/4 cup epsom salts (magnesium sufate) 1/2 cup water shallow bowl or dish sponge (optional) or other porous type material food coloring (optional) More How To's from your Guide To Chemistry http://chemistry.about.com/cs/ht.htm How To Grow Table Salt or Sodium Chloride Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Table salt or sodium chloride crystals are great crystals to try if you've never grown crystals before because it's easy to find salt and water (the ingredients), the crystals are non-toxic, and no special equipment is required. Let's get started! Difficulty: Easy Time Required: a few hours to several days, depending on your method Here's How: 1. Stir salt into boiling hot water until no more salt will dissolve (crystals start to appear at the bottom of the container). Be sure the water is as close to boiling as possible. Hot tap water is not sufficient for making the solution. 2. If you want crystals quickly, you can soak a piece of cardboard in this supersaturated salt solution. Once it is soggy, place it on a plate or pan and set it in a warm and sunny location to dry out. Numerous small salt crystals will form. 3. If you are trying to form a larger, perfect cubic crystal, you will want to make a seed crystal. 4. To grow a big crystal from a seed crystal, carefully pour the supersaturated salt solution into a clean container (so no undissolved salt gets in), allow the solution to cool, then hang the seed crystal in the solution from a pencil or knife placed across the top of the container. You could cover the container with a coffee filter if you like. 5. Set the container in a location where it can remain undisturbed. You are more likely to get a perfect crystal instead of a mass of crystals if you allow the crystal to grow slowly (cooler temperature, shaded location) in a place free of vibrations. Tips: 1. Experiment with different types of table salt. Try iodized salt, uniodized salt, sea salt, or even salt substitutes. Try using different types of water, such as tap water compared with distilled water. See if there is any difference in the appearance of the crystals. 2. If you are trying for the 'perfect crystal' use uniodized salt and distilled water. Impurities in either the salt or water can aid dislocation, where new crystals don't stack perfectly on top of previous crystals. What You Need: table salt - sodium chloride water clean clear container piece of cardboard (optional) string and pencil or butter knife (optional) How To Grow Purple Chromium Alum Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Learn how to grow deep purple or lavender cubic crystals of potassium chromium sulphate dodecahydrate. In addition, you can grow clear crystals around the purple crystals, yielding a sparkling crystal with a purple core. The same technique can be applied to other crystal systems. Difficulty: Average Time Required: days to months depending on desired size Here's How: 1. The growing solution will consist of a chromium alum solution mixed with an ordinary alum solution. Make a chromiun alum solution by mixing 60 g of potassium chromium sulfate in 100 ml water (or 600 g chromium alum per liter of water). 2. In a separate container, prepare a saturated solution of ordinary alum by stirring alum into warm water until it will no longer dissolve. 3. Mix the two solutions in any proportion that you like. The more deeply colored solutions will produce darker crystals, but it will also be harder to monitor crystal growth. 4. Grow a seed crystal using this solution, then tie it to a string and suspend the crystal in the remaining mixture. 5. Loosely cover the container with a coffee filter or paper towel. At room temperature (~25°C), the crystal can be grown via slow evaporation for as little time as a few days or as long as a few months. 6. To grow a clear crystal over a colored core of this or any other colored alum, simply remove the crystal from the growing solution, allow it to dry, and then re- immerse it in a saturated solution of ordinary alum. Continue growth for as long as desired. Tips: 1. A saturated solution of pure chrome alum will grow darker crystals, but the solution will be too dark to see through. Feel free to increase the concentration of chrome alum, but be aware that the solution becomes deeply colored. 2. Notice that the chrome alum solution is a dark blue-green, but the crystals are purple! What You Need: potassium chromium sulfate string (chromium alum) coffee filter or paper towel alum pencil, knife, or stick (to suspend water string) clear glass jar spoon or stirring rod How To Grow Red Potassium Ferricyanide Crystals From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Grow red crystals without dye! Potassium ferricyanide (K3Fe(CN)6), also known as 'Red Prussiate of Potash', makes beautiful red monoclinic crystals. Don't be too concerned about the 'cyanide' part of the chemical name. You shouldn't eat your crystals or drink the liquid, but it's safe to grow these crystals on a countertop or pour your waste down the drain. Difficulty: Average Time Required: one or more weeks Here's How: 1. Place 93 grams of potassium ferricyanide and 200 ml warm water into a clear container. 2. Stir to dissolve. 3. If you wish to grow a single large crystal, pour a few drops of this solution onto a saucer or other shallow dish (perhaps with a string laid across the liquid, otherwise tie crystals from the plate onto a string). Allow this liquid to evaporate to form seed crystals. Tie the string to a pencil or butter knife to suspend the string into the original container, being careful not to touch the sides or bottom of the container. 4. Cover the container with a paper towel or coffee filter. You want evaporation to occur, but you don't want contaminants to be able to fall into your crystal-growing solution. 5. Leave your solution undisturbed, but check on it from day to day to watch your crystals grow. 6. Once the crystals have reached the desired size (probably after a week or two), remove the crystal and allow it to dry on a paper towel. Once dry, you can store your crystal wrapped in a piece of tissue. 7. Alternatively, you could allow all of the liquid to evaporate from the container (takes about a month, depending on ambient temperature and humidity). Tips: 1. If you are having trouble getting all of the solid to dissolve, try using hotter water. If the solid still won't dissolve, allow the solution to settle out, then use only the clear portion for growing crystals (decant it or carefully pour it the solution into a clean container). If you have solids in your starting solution, the crystals will form (nucleate) around the particles and the resulting crystals will be smaller than if you used a clear solution. What You Need: 93 g potassium ferricyanide string/pencil (optional) spoon or 200 ml warm water stirring rods clear glass or plastic container coffee filter or paper towel How To Make Peppermint Cream Wafers From Anne Marie Helmenstine, Ph.D.,Your Guide to Chemistry. Cooking is really an artistic variation of chemistry! Here's a fun and easy Christmas holiday project for the chemistry lab. Make these peppermint cream wafers for a seasonal project or demonstration. Difficulty: Average Time Required: 30 minutes Here's How: 1. First, make sure all of the measuring utensils and glassware are clean and dry. If possible, use beakers that have never been used for more tradition chemistry experiments, since residues of chemicals can remain in the glass. 2. Measure and mix the following chemicals in a 250-ml beaker: 1/4 cup or 2 tablespoons or 2 level medicine cups of sugar; 8 ml (1.5 tsp) milk; 10 ml (2 tsp) Karo syrup; 1/4 tsp or pea-sized amount of cream of tartar. 3. Heat the mixture until its temperature reaches 200°F, stirring often. 4. Once the temperature reaches 200°F, cover the beaker (with foil) and remove it from the heat for 2 minutes. 5. Return the mixture to the heat. Heat and stir until the temperature reaches 240°F (soft-ball on a candy thermometer). 6. Remove the mixure from heat and add one drop of peppermint oil and 1-2 drops of food coloring. 7. Stir until the mixture is smooth, but not any longer than that or else the candy could harden in the beaker. Avoid stirring longer than 15-20 seconds. 8. Pour coin-sized drops of the mixture onto a sheet of foil. Depending on the size of the drops, you will get 8-12 of them. Allow the candy to cool, then peel the drops off to enjoy your treat! Hot water is sufficient for clean-up. Tips: 1. You can use wooden tongue depressors or metal spoons for stirring. 2. Disposable plastic measuring cups, such as those used to dispense liquid medications, work well for measuring the ingredients for a lab of students. 3. The mixture can be heated over a hotplate or a bunsen burner, with a ring stand and wire gauze pad. You could also use a stove. 4. The texture of the finished product depends on the heating/cooling of the sugar mixture. You could get jellied candies or rock candy. It's a nice opportunity to discuss crystal structures. What You Need: sucrose (table sugar) oil of peppermint concentrated liquid sucrose (or 250 ml beaker or a saucepan Karo syrup) candy thermometer or other potassium tartrate (cream of metal-backed thermometer tartar) aluminum foil lactose (we will use milk) assorted labware or utensils for food coloring stirring, When you make rock candy, you can see the shape of sugar crystals on a giant scale. The key is giving them lots of time (about 7 days) to grow. As the water evaporates, sugar crystals form on the string or stick, and the shapes that they form reflect the shape of individual sugar crystals. Learn more about sugar and crystals. Recipe Conversions (Note: Recipe annotations will appear in a new window.) Table sugar crystals, Rock candy crystals, magnified 100 times magnified 250 times Notice that the shapes of the rock candy crystals are very similar to those of the sugar crystals. That’s because rock candy is made up of many sugar crystals that have grown together. (Images courtesy of FEI Company) What Do I Need? • 4 cups sugar • 2 cups water • a small saucepan • a wooden spoon • a candy thermometer • a small, clean glass jar • a measuring cup • cotton string • a weight to hang on the string (such as a screw or galvanized washer) • waxed paper • a pencil (to suspend the string in the jar) What Do I Do? 1. Heat the water in the saucepan over medium-high heat until it comes to a boil. 2. Completely dissolve the sugar in the boiling water, stirring continuously with the wooden spoon until the solution grows clear and it reaches a rolling boil. 3. Remove the solution from the heat, and then carefully pour it into the jar. Cover the jar with a small piece of waxed paper. 4. Tie the weight to one end of the string, and then tie the other end to the middle of the pencil. The string should be about two-thirds as long as the jar is deep. Dip the string into the sugar solution, remove it, lay it on a piece of waxed paper, straighten it out, and let it dry for a few days. • Why does the string need to be soaked and then dried? 5. Gently suspend the prepared string in the solution and let sit at room temperature, undisturbed, for several days. You can check each day to see how much your crystals have grown. It’s tempting, but don’t touch the jar until the experiment is finished—it usually takes about seven days. • What makes the crystals grow? 6. At the end of the week, the crystals on your string should be clearly defined, with sharp right angles and smooth faces of various sizes. In the field of crystallography, these are called monoclinic crystals. Their shape is determined by the way the individual sugar molecules fit together, which is similar to the way the shape of a pile of oranges is determined by the shape of the individual oranges and the way they stack together. What Else Can I Try? • Try adding food coloring or flavoring to your sugar syrup before making the rock candy.
Pages to are hidden for
"Crystal Recipes - DOC"Please download to view full document