Note: Food coloring may stain hands, clothes, and surfaces. Take appropriate precautions.
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Shaving cream is made of solid soap, water, and a gas. Soap molecules have two ends; one that loves water (hydrophilic) and one that avoids water (hydrophobic). The hydrophilic end is typically called the head, and the hydrophobic end is the tail. Water is a polar molecule, meaning it has a positive side and a negative side. The hydrophilic end of soap is also polar, which is why it is attracted to the water. The hydrophobic tail is nonpolar. Food coloring is dye dissolved in water, so it is also hydrophilic. When you add the food coloring to the shaving cream, it will only react with the heads of the soap molecules, not the tails.
Paper is made of cellulose which are long molecules made of glucose, a type of sugar. Glucose molecules, and therefore cellulose, are hydrophilic. When you press your paper to the shaving cream and food coloring, the food coloring can react with the paper’s cellulose because they are both hydrophilic, so the colors can spread through the paper easily. This is why the marbled pattern on your paper doesn’t exactly match what you saw on the shaving cream!
Marbling paper is an ancient art dating back to the 10th century in China, the 12th century in Japan, and the 17th century in Europe. It gets its name because the patterns on the paper are similar to those in smooth marble and other stones. The art of paper marbling is still popular around the world today, and there are a variety of techniques used!
Variety of candy pieces, preferably gummy (e.g., gumdrops, jelly beans, or fruit snacks)
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You probably discovered that squares & cubes easily collapse when too much weight is put on top (compression). Round shapes like circles & spheres or, more commonly in architecture, arches & domes are stronger than squares, but you may have discovered that triangles make the strongest structures. The pyramids in Egypt are based on triangles and have stood for centuries! Have you ever climbed on a geodesic dome at a playground? The triangles give it strength!
Triangles are strong shapes for engineering structures because compression on one side of the triangle is balanced by a pull (i.e. tension) on the other side, so the whole structure can’t collapse like a square. The way to squash a triangle is to break one of the sides, which requires a lot of weight!
If you tried to build a tall tower out of cubes, how did it hold up when you added weight to the top? Try to build the tower again, but this time add toothpicks inside the cube between opposite corners to make triangles inside the cube; this should make your tower stronger. Can you think of any other structures you’ve seen that use triangles for strength?
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We used boiling water for this experiment so we could dissolve more Borax in the water than if we’d used cooler water. The hot water molecules move around more quickly and are farther apart from each other than cold or even room temperature water molecules, leaving more space for Borax molecules to dissolve into the water – more of them “fit” in the water because of the extra space between the hot water molecules. The hot solution with a lot of Borax dissolved in it is called a supersaturated solution! As the solution cools, the Borax begins to crystalize on the pipe cleaner because the water can’t hold that much Borax anymore. At room temperature, it holds less Borax; this is called a saturated solution.
Crystals started forming when the solution was supersaturated. The pipe cleaner and string give the molecules something to hold onto. The molecules then stack onto each other like blocks. More Borax molecules attach to these small starter crystal “seeds,” which keeps the crystals “growing” until most of the Borax has crystalized. This keeps happening and it looks like the crystals are growing, but they aren’t alive. The crystals will “grow” until there isn’t any Borax left or until you take your snowflake out of the solution.
Were your crystals big or small? The more time the solution has to cool, the bigger the crystals will get until they reach their maximum size. If we cool the solution quickly, say by putting the jar of hot water in a bucket of ice, the crystals will be smaller because the Borax molecules don’t have much time to organize themselves and join together to make big crystals.
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White vinegar is acetic acid, and the eggshell is mostly calcium carbonate. The acetic acid reacts with the calcium carbonate to form calcium acetate, carbon dioxide (the bubbles you see), and water, resulting in a dissolved eggshell.
CaCO3 (s) + 2 HC2H3O2 (aq) → Ca(C2H3O2)2 (aq) + H2O (l) + CO2 (g)
Most household white vinegar is only 5% acetic acid with the other 95% being water. When one of the two reactants in the chemical equation is used up, the reaction stops because it’s out of ingredients. In this reaction, the acetic acid is likely to be the limiting reagent, and that’s why some of the eggshell needs to be washed away – there wasn’t enough acetic acid to completely dissolve the shell.
Another process happens at the same time and causes the egg to swell. The water in the vinegar crosses the egg's membrane by osmosis and stretches the membrane, making the egg bigger. The membrane holds the egg together even though there is no shell, but water can pass through because the membrane is semipermeable. Osmosis is the scientific term for this movement into and out of the membrane, and the goal is to make the amount of water on each side of the egg membrane equal. If you put your egg in corn syrup, the egg shrinks because the water is leaving; there is less water in the syrup than in the egg, so water has to leave the egg until the two sides have equal amounts. If you let your egg sit open to air for a few days, the semipermeable membrane allows the water to evaporate until your egg shrinks and you are left with the yolk in the membrane.
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You should have observed a pattern melted into your marshmallow layer. Why didn’t all of the marshmallows melt at the same time?
Microwaves are a type of electromagnetic radiation, like visible light. We can’t see them because they are outside of the range of visible light. A microwave oven generates a standing wave inside the oven. A standing wave is a wave that is reflected back and forth and interferes with itself, creating peaks with higher amplitude and troughs with zero amplitude. The wave peaks heat faster than the troughs and lead to “hot spots” in the microwave; these are the areas where the marshmallows melted. The distance between “hot spots” is half the wavelength of the standing wave in the oven, so the equation multiplies by two.
Microwaves work well for cooking food because the waves are at an energy that can be easily absorbed by molecules common in food, especially water molecules. The absorbed energy heats the food thereby cooking it. Be sure to put the rotating plate back in your microwave! The rotation ensures that all parts of the food go through the “hot” and “cold” spots in the microwave to cook food evenly.
"For a tasty end to your experiment, our testers suggested adding chocolate chips or chocolate sauce and broken graham crackers to the marshmallows, and taste-testing the result!"