Kitchen Science Experiments

How To Make a Rainbow in a Glass Density Demonstration???

 

You don't have to use lots of different chemicals to make a colorful density column. This project uses colored sugar solutions made at different concentrations. The solutions will form layers, from least dense, on top, to most dense (concentrated) at the bottom of the glass.

Difficulty: Easy

Time Required: minutes

Here's How:

1. Line up five glasses. Add 1 tablespoon (15 g) of sugar to the first glass, 2 tablespoons (30 g) of sugar to the second glass, 3 tablespoons of sugar (45 g) to the third glass, and 4 tablespoons of sugar (60 g) to the fourth glass. The fifth glass remains empty.
2. Add 3 tablespoons (45 ml) of water to each of the first 4 glasses. Stir each solution. If the sugar does not dissolve in any of the four glasses, then add one more tablespoon (15 ml) of water to each of the four glasses.
3. Add 2-3 drops of red food coloring to the first glass, yellow food coloring to the second glass, green food coloring to the third glass, and blue food coloring to the fourth glass. Stir each solution.
4. Now let's make a rainbow using the different density solutions. Fill the last glass about one-fourth full of the blue sugar solution.
5. Carefully layer some green sugar solution above the blue liquid. Do this by putting a spoon in the glass, just above the blue layer, and pouring the green solution slowly over the back of the spoon. If you do this right, you won't disturb the blue solution much at all. Add green solution until the glass is about half full.
6. Now layer the yellow solution above the green liquid, using the back of the spoon. Fill the glass to three-quarters full.
7. Finally, layer the red solution above the yellow liquid. Fill the glass the rest of the way.

Tips:

1. The sugar solutions are miscible, or mixable, so the colors will bleed into each other and eventually mix.
2. If you stir the rainbow, what will happen? Because this density column is made with different concentrations of the same chemical (sugar or sucrose), stirring would mix the solution. It would not un-mix, like you would see with oil and water.
3. Try to avoid using gel food colorings. As you can see in my photo, it is difficult for young children to mix them into the solution.
4. If your sugar won't dissolve, an alternative to adding more water is to nuke the solutions for about 30 seconds in the microwave or to use warm water in the first place. If you heat the water, use care to avoid burns.
5. If you want to make layers you can drink, try substituting unsweetened soft drink mix for the food coloring, or four flavors of sweetened mix for the sugar plus coloring.

What You Need

• sugar
• water
• food coloring
• tablespoon
• 5 glasses or clear plastic cups.

 

 

How To Build a Baking Soda Volcano???

Okay, the baking soda volcano is the kitchen equivalent of a volcano, not a real one. It's cool all the same! The baking soda volcano is also non-toxic, which adds to its appeal.

Difficulty: Average

Time Required: 30 minutes

Here's How:

1. First make the 'cone' of the baking soda volcano. Mix 6 cups flour, 2 cups salt, 4 tablespoons cooking oil, and 2 cups of water. The resulting mixture should be smooth and firm (more water may be added if needed).
2. Stand the soda bottle in the baking pan and mold the dough around it into a volcano shape. Don't cover the hole or drop dough into it.
3. Fill the bottle most of the way full with warm water and a bit of red food color (can be done before sculpting if you don't take so long that the water gets cold).
4. Add 6 drops of detergent to the bottle contents. The detergent helps trap the bubbles produced by the reaction so you get better lava.
5. Add 2 tablespoons baking soda to the liquid.
6. Slowly pour vinegar into the bottle. Watch out - eruption time!

Tips:

1. The cool red lava is the result of a chemical reaction between the baking soda and vinegar.
2. In this reaction, carbon dioxide gas is produced, which is also present in real volcanoes.
3. As the carbon dioxide gas is produced, pressure builds up inside the plastic bottle, until the gas bubbles (thanks to the detergent) out of the 'volcano'.
4. Adding a bit of food coloring will result in red-orange lava! Orange seems to work the best. Add some red, yellow, and even purple, for a bright display.
5. If you need more detailed instructions or information about the chemical reactions involved in the volcano, I also have a step-by-step tutorial and a video tutorial.

What You Need

• 6 cups flour
• 2 cups salt
• 4 tablespoons cooking oil
• warm water
• plastic soda bottle
• dishwashing detergent
• food coloring
• vinegar
• baking dish or other pan
• 2 T baking soda

  Invisible Inks 

  Sometimes people tell me they can't do any science projects because they don't have any chemicals. There are some activities that don't require any chemicals you don't already have. A great example is invisible ink.

  Invisible ink is any substance that you can use to write a message that is invisible until the ink is revealed. You use the ink by writing your message with it using a cotton swab, dampened finger, fountain pen, or toothpick. Let the message dry. You may want to write a normal message on the paper so that it doesn't appear to be blank and meaningless. If you write a cover message, use a ballpoint pen, pencil, or crayon, since fountain pen ink could run into your invisible ink. Avoid using lined paper to write your invisible message, for the same reason.
  
  How you reveal the message depends on the ink you used. Most invisible inks are made visible by heating the paper. Ironing the paper or holding it over a 100-watt bulb are easy ways to reveal these types of messages. Some messages are developed by spraying or wiping the paper with a second chemical. Other messages are revealed by shining an ultraviolet light on the paper.
  Make Invisible Ink
  Anyone can write an invisible message, assuming you have paper, because body fluids can be used as invisible ink. If you don't feel like collecting urine, here are some alternatives:
  Heat-Activated Invisible Inks
  Iron the paper, set it on a radiator, place it in an oven (set lower than 450° F), hold it up to a hot light bulb.
• any acidic fruit juice (e.g., lemon, apple, or orange juice)
• onion juice
• baking soda (sodium bicarbonate)
• vinegar
• white wine
• dilute cola
• diluted honey
• milk
• soapy water
• sucrose (table sugar) solution
• urine

Inks Developed by Chemical Reactions
These inks are sneakier, because you have to know how to reveal them. Most of them work using pH indicators, so when it doubt, paint or spray a suspected message with a base (like sodium carbonate solution) or an acid (like lemon juice). Some of these inks will reveal their message when heated (e.g., vinegar).

• phenolphthalein (pH indicator), developed by ammonia fumes or sodium carbonate (or another base)
• thymolphthalein, developed by ammonia fumes or sodium carbonate (or another base)
• vinegar or dilute acetic acid, developed by red cabbage water
• ammonia, developed by red cabbage water
• sodium bicarbonate (baking soda), developed by grape juice
• sodium chloride (table salt), developed by silver nitrate
• copper sulfate, developed by sodium iodide, sodium carbonate, potassium ferricyanide, or ammonium hydroxide
• lead(II) nitrate, developed by sodium iodide
• iron sulfate, developed by sodium carbonate, sodium sulfide, or potassium ferricyanide
• cobalt chloride, developed by potassium ferricyanide
• starch (e.g., corn starch or potato starch), developed by iodine solution
• lemon juice, developed by iodine solution

Inks Developed by Ultraviolet Light (Black Light)
Most of the inks that become visible when you shine a black light on them also would become visible if you heated the paper. Glow-in-the-dark stuff is still cool. Here are some chemicals to try:

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

Any chemical that weakens the structure of paper can be used as an invisible ink, so you might find it fun to discover other inks around your home or lab.

Rubber Egg & Chicken Bones

A Mad Scientist can make a toy out of just about anything, including a boiled egg. Soak an egg in a common kitchen ingredient, vinegar, to dissolve its shell and make the egg rubbery enough that you can bounce it on the floor like a ball. Soaking chicken bones in vinegar will soften them so that they will become rubbery and flexible.

Rubber Egg Materials

• hard-boiled egg
• glass or jar, big enough to hold the egg
• vinegar

Turn the Egg into a Bouncy Ball

1. Place the egg in the glass or jar.
2. Add enough vinegar to completely cover the egg.
3. Watch the egg. What do you see? Little bubbles may come off the egg as the acetic acid in the vinegar attacks the calcium carbonate of the eggshell. Over time the color of the eggs may change as well.
4. After 3 days, remove the egg and gently rinse the shell off of the egg with tap water.
5. How does the boiled egg feel? Try bouncing the egg on a hard surface. How high can you bounce your egg?
6. You can soak raw eggs in vinegar for 3-4 days, with a slightly different result. The eggs shell will become soft and flexible. You can gently squeeze these eggs, but it's not a great plan to try to bounce them on the floor.

Make Rubbery Chicken Bones If you soak chicken bones in vinegar (the thinner bones work best), the vinegar will react with the calcium in the bones and weaken them so that they will become soft and rubbery, as if they had come from a rubber chicken. It is the calcium in your bones that makes them hard and strong. As you age, you may deplete the calcium faster than you replace it. If too much calcium is lost from your bones, they may become brittle and susceptible to breaking. Exercizing and eating a diet that includes calcium-rich foods can help prevent this from happening.

Red Cabbage pH Indicator...

Make your own pH indicator solution! Red cabbage juice contains a natural pH indicator that changes colors according to the acidity of the solution. Red cabbage juice indicator is easy to make, exhibits a wide range of colors, and can be used to make your own pH paper strips (watch the video).

Introduction

Red cabbage contains a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purplish color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.
The color of the juice changes in response to changes in its hydrogen ion concentration. pH is the -log[H+]. Acids will donate hydrogen ions in an aqueous solution and have a low pH (pH < 7). Bases accept hydrogen ions and have a high pH (pH > 7).

Materials

• red cabbage
• blender or knife
• boiling water
• filter paper (coffee filters work well)
• One large glass beaker or other glass container
• Six 250 mL beakers or other small glass containers
• household ammonia (NH₃)
• baking soda (sodium bicarbonate, NaHCO₃)
• washing soda (sodium carbonate, Na₂CO₃)
• lemon juice (citric acid, C₆H₈O₇)
• vinegar (acetic acid, CH₃COOH)
• cream of tartar (Potassium bitartrate, KHC₄H₄O₆)
• antacids (calcium carbonate, calcium hydroxide, magnesium hydroxide)
• seltzer water (carbonic acid, H₂CO₃)
• muriatic acid or masonry's cleaner (hydrochloric acid, HCl)
• lye (potassium hydroxide, KOH or sodium hydroxide, NaOH)

Procedure

1. Chop the cabbage into small pieces until you have about 2 cups of chopped cabbage. Place the cabbage in a large beaker or other glass container and add boiling water to cover the cabbage. Allow at least ten minutes for the color to leach out of the cabbage. (Alternatively, you can place about 2 cups of cabbage in a blender, cover it with boiling water, and blend it.)
2. Filter out the plant material to obtain a red-purple-bluish colored liquid. This liquid is at about pH 7. (The exact color you get depends on the pH of the water.)
3. Pour about 50 - 100 mL of your red cabbage indicator into each 250 mL beaker.
4. Add various household solutions to your indicator until a color change is obtained. Use separate containers for each household solution - you don't want to mix chemicals that don't go well together!

Notes

• This demo uses acids and bases, so please make certain to use safety goggles and gloves, particularly when handling strong acids (HCl) and strong bases (NaOH or KOH).
• Chemicals used in this demo may be safely washed down the drain with water.
• A neutralization experiment could be performed using cabbage juice indicator. First add an acidic solution such as vinegar or lemon juice until a reddish color is obtained. Then add baking soda or antacids to return the pH towards a neutral 7.
• You can make your own pH paper strips using red cabbage indicator. Take filter paper (or coffee filter) and soak it in a concentrated red cabbage juice solution. After a few hours, remove the paper and allow it to dry (hang it by a clothespin or string). Cut the filter into strips and use them to test the pH of various solutions.

Red Cabbage pH Indicator Colors

pH	2	4	6	8	10	12
Color	Red	Purple	Violet	Blue	Blue-Green	Greenish Yellow

Pepper and Water Science Magic Trick...

The pepper and water science trick is one of the easiest magic tricks you can perform. Here's how to do the trick and an explanation of how it works.

Materials for the Pepper & Water Trick

You only need a few common kitchen ingredients to perform this science magic trick.

• black pepper
• water
• dishwashing liquid
• plate or bowl

Performing the Pepper & Water Trick

1. Pour water into a plate or bowl.
2. Shake some pepper onto the water.
3. If you dip your finger into the pepper and water, nothing much happens.
4. If you put a drop of dishwashing liquid on your finger and then dip it into the pepper and water the pepper will rush to the outer edges of the dish. If you are doing this as a 'trick' then you might have one finger that is clean and another finger that you dipped in detergent before performing the trick.

How the Pepper & Water Trick Works

When you add detergent to water the surface tension of the water is lowered. Water normally bulges up a bit, like what you see when you look at a water drop. When the surface tension is lowered, the water wants to spread out. As the water flattens on the dish, the pepper that is floating on top of the water is carried to the outer edge of the plate as if by magic.

Hot Ice or Sodium Acetate

Sodium acetate or hot ice is an amazing chemical you can prepare yourself from baking soda and vinegar. You can cool a solution of sodium acetate below its melting point and then cause the liquid to crystallize. The crystallization is an exothermic process, so the resulting ice is hot. Solidification occurs so quickly you can form sculptures as you pour the hot ice.

Sodium Acetate or Hot Ice Materials

• 1 liter clear vinegar (weak acetic acid)
• 4 tablespoons baking soda (sodium bicarbonate)

Prepare the Sodium Acetate or Hot Ice

1. In a saucepan or large beaker, add baking soda to the vinegar, a little at a time and stirring between additions. The baking soda and vinegar react to form sodium acetate and carbon dioxide gas. If you don't add the baking soda slowly, you'll essentially get a baking soda and vinegar volcano, which would overflow your container. You've made the sodium acetate, but it is too dilute to be very useful, so you need to remove most of the water. Here is the reaction between the baking soda and vinegar to produce the sodium acetate:
   Na⁺[HCO₃]^– + CH₃–COOH → CH₃–COO^– Na⁺ + H₂O + CO₂
   
2. Boil the solution to concentrate the sodium acetate. You could just remove the solution from heat once you have 100-150 ml of solution remaining, but the easiest way to get good results is to simply boil the solution until a crystal skin or film starts to form on the surface. This took me about an hour on the stove over medium heat. If you use lower heat you are less likely to get yellow or brown liguid, but it will take longer. If discoloration occurs, it's okay.
3. Once you remove the sodium acetate solution from heat, immediately cover it to prevent any further evaporation. I poured my solution into a separate container and covered it with plastic wrap. You should not have any crystals in your solution. If you do have crystals, stir a very small amount of water or vinegar into the solution, just sufficient to dissolve the crystals.
4. Place the covered container of sodium acetate solution in the refrigerator to chill.

Activities Involving Hot Ice

The sodium acetate in the solution in the refrigerator is an example of a supercooled liquid. That is, the sodium acetate exists in liquid form below its usual melting point. You can initiate crystallization by adding a small crystal of sodium acetate or possibly even by touching the surface of the sodium acetate solution with a spoon or finger. The crystallization is an example of an exothermic process. Heat is released as the 'ice' forms. To demonstrate supercooling, crystallization, and heat release you could:

• Drop a crystal into the container of cooled sodium acetate solution. The sodium acetate will crystallize within seconds, working outward from where you added the crystal. The crystal acts as a nucleation site or seed for rapid crystal growth. Although the solution just came out of the refrigerator, if you touch the container you will find it is now warm or hot.
• Pour the solution onto a shallow dish. If the hot ice does not spontaneously begin crystallization, you can touch it with a crystal of sodium acetate (you can usually scrape a small amount of sodium acetate from the side of the container you used earlier). The crystallization will progress from the dish up toward where you are pouring the liquid. You can construct towers of hot ice. The towers will be warm to the touch.
• You can re-melt sodium acetate and re-use it for demonstrations.

Hot Ice Safety

As you would expect, sodium acetate is a safe chemical for use in demonstrations. It is used as a food additive to enhance flavor and is the active chemical in many hot packs. The heat generated by the crystallization of a refrigerated sodium acetate solution should not present a burn hazard.

Hot Ice Help

Answers to common questions about hot ice are available that should help solve any problems you may encounter with this project. There is also a video tutorial showing how to make hot ice.

Black Snakes or Glow Worms

Black snakes, sometimes called glow worms, are small tablets that you light, using a punk or a lighter, that burn to produce long black 'snakes' of ash. They produce some smoke (which had a characteristic, probably toxic odor), but no fire or explosion. The original fireworks used to contain salts of a heavy metal (such as mercury), so while they were marketed for kids to play with, they really weren't that much safer than conventional fireworks, just dangerous in a different way. However, there is a safe way to make black snakes. You can heat baking soda (sodium bicarbonate) with sugar (sucrose) to produce carbon dioxide gas that puffs up black carbon ash.

Soda & Sugar Black Snake Materials

• sand
• alcohol or fuel oil (I didn't have any high-proof alcohol on hand, so I used lighter fluid left over from the handheld fireballs project)
• baking soda
• sugar (I used powdered sugar, but you can grind table sugar in a coffee grinder)

Make Snakes

• Mix 4 parts powdered sugar with 1 part baking soda. (I used 4 tsp sugar and 1 tsp baking soda.)
• Make a mound with the sand. Push a depression into the middle of the sand.
• Pour the alcohol or other fuel into the sand to wet it.
• Pour the sugar and soda mixture into the depression.
• Ignite the mound, using a lighter or match.

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. 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
These instructions were adapted from a tutorial given on Boing Boing which in turn came from a Russian site. The Russian site goes on to suggest two additional ways to make chemical snakes:
Ammonium Nitrate Black Snake
This works the same way as the sugar and baking soda snake, except you use ammonium nitrate (niter) instead of sugar. Mix one part ammonium nitrate and one part baking soda. This recipe is more like what you would see in commercial black snake fireworks, which are supposedly composed of soda with nitrated naphthalenes and linseed oil. It's another very safe demonstration, though not safe enough to eat, like sugar and baking soda.
Ammonium Dichromate Green Snake
The green snake is a variation on the ammonium dichromate volcano. The volcano is a cool chemistry demonstration (orange sparks, green ash, smoke), but it's a chemistry-lab-only demonstration (not safe for kids at all) because the chromium compound is toxic. The green soda snakes are made from:

• two parts of ammonium nitrate
• one part of powdered sugar
• one part of ammonium dichromate

Mix the ingredients, add a small amount of water, and roll the result into a snake shape (gloves please!). Allow the snake to dry (the tutorial suggests using a hairdryer to speed the process). Light one end of the snake. In this case, an orange snake burns to green ash. It's worth knowing how to do this demonstration if you have ammonium dichromate and ammonium nitrate on hand, otherwise let the Russian photos suffice and play with the sugar and baking soda snakes instead. Another (spectacular) form of black carbon snake results from reacting sugar and sulfuric acid.

Glowing Bubbles

Bubbles are already awesome, but glowing bubbles are even better. It is easy and safe to make bubbles glow, plus it doesn't require any hard-to-find materials. Here is what you do.

Glowing Bubble Materials

• bubble solution
• glow in the dark solution (can use washable glow paint or can make glow solution)
• bubble wand

Make Glowing Bubbles

1. Mix bubble solution with glow solution.
2. The only 'trick' is making sure you have enough bubble solution to make strong bubbles and enough glowing solution to get a good glow. Try a 50:50 mix to start. You can add more glow liquid or more bubble solution, depending on your results.

How to Make Glow Solution If you use washable glowing paint and add that to the bubble solution, your bubbles will glow in the dark after the solution has been exposed to bright light. Sometimes it can be difficult to find washable glowing paint, so you may wish to make glowing water using a highlighter pen. This solution mixes about 50:50 with bubble solution to make glowing bubbles. The color of the glow depends on the highlighter that you use. Highlighter pens fluoresce, which means you will need to shine a black light on the bubbles to get them to glow. Check your pen with a black light before you cut it open. Yellow almost always glows. Green and orange are good too, but a lot of blue and red pens don't glow. Here is how you make the glow solution:

1. Use a knife to (carefully) cut a highlighter pen in half. It's a pretty simple steak knife and cutting board procedure.
2. Pull out the ink-soaked felt that is inside the pen.
3. Soak the felt in a small quantity of water. I made a video of what to expect.
4. Use the dyed water to make bubble solution or for other glowing projects.

Glowing Bubble Safety and Clean-Up The glowing bubble solution is very safe, providing you used either non-toxic washing glow paint or a non-toxic highlighter pen. I would recommend blowing the bubbles outdoors so that you don't have to wash glowing liquid off of walls or furniture. Bubble solution is already pretty soapy, so clean up any spills with lots of water. One nice thing about cleaning up glowing bubble solution is you can see the spots made by the bubble solution very easily.