Red, White and Blue Electrolysis Chemistry Demonstration

Patriotic Colors Chem Demo

Author
by Anne Marie Helmenstine, Ph.D.

Here is a perfect electrochemistry chem demo for the 4th of July or other patriotic holiday. Use salt bridges to connect three beakers of liquids (clear, red, clear). Apply a voltage and watch the solutions turn red, white and blue.

PATRIOTIC COLORS ELECTROLYSIS DEMO MATERIALS

• 500 mL 1M potassium nitrate, KNO₃(make this)
• 1 mL thymolphthalein indicator solution (make this)
• 2 mL phenolphthalein solution (make this)

• approximately 2 mL 0.1M sodium hydroxide, NaOH (make this)
• approximately 1 mL 0.1M sulfuric acid, H₂SO₄ (make this)
• 3 250-mL beakers
• 3 8-mm x 200-mm carbon rods
• 25-cm uninsulated 14-ga copper wire
• 10-cm rubber tubing, approximately 5-mm outside diameter
• #6 rubber stopper, 1-hole
• 2 U-tubes, 100-mm, 13-mm outside diameter
• 4 cotton balls
• 3 20-cm glass stirring rods
• adjustable DC power supply that can produc 1 amp at 10 volts (e.g., automotive battery charger)
• clip leads

PREPARE THE RED, WHITE, AND BLUE DEMONSTRATION

1. 
   
2. 1) Pour 150 mL of 1.0M KNO₃ into each of the three beakers.
    2) Line the beakers up in a row. Place a carbon electrode in each beaker.
3.  3) Wrap one end of the copper wire around one the carbon electrodes at the end of the row. Slip rubber tubing over the copper wire to cover the exposed wire that will be between the electrodes. Wrap the other end of the copper wire around the third carbon electrode, at the end of the row of beakers. Skip the center carbon rod and be sure no exposed copper touches it.
4.  4) Fill the two U-tubes with 1M KNO₃ solution. Plug the ends of each tube with cotton balls. Invert one of the U-tubes and hang it over the rim of the left and center beaker. The arms of the U-tube should be immersed in the liquid. Repeat the procedure with the second U-tube and the center and right beakers. There should not be an air bubble in either U-tube. If there is, remove the tube and re-fill it with KNO₃ solution.

1. 5) Place a glass stirring rod in each beaker.
    6) Make certain the power supply is off and then connect the positive (+) terminal to the central carbon electrode and the negative (-) terminal to one of the outer carbon electrodes.

1. 7) Add 1 mL of thymolphthalein solution to the beaker on the right and 1 mL of phenolphthalein indicator to each of the other two beakers.
    8) Add 1 mL of 0.1M NaOH solution to the middle beaker. Stir the contents of each beaker. From left to right, the solutions should be: clear, red, clear.
2.  9) These solutions may be stored in sealed containers and may be re-used to repeat the demonstration. If the colors become faint, more indicator solution may be added.

PERFORM THE DEMONSTRATION

1. 1) Turn on the power supply. Adjust it to 10 volts.
    2) Wait 15 minutes. Turn off the power supply and stir each solution.
2.  3) At this point, the solutions should now appear red, colorless and blue. You may wish to place a white sheet of paper or posterboard behind the beakers to display the colors. Also, this makes the center beaker appear white.
3.  4) You can return the solutions to their original colors by reversing the connections to the power supply adjusting it to 10 volts, and allowing 20 minutes before turning off the power and stirring the solutions.
4.  5) Another way to return the solutions to their original colors is to add 0.1 M H₂SO₄ to the beakers on the end until the liquids turn colorless. Add 0.1 M NaOH to the middle beaker until the liquid turns from clear to red.

DISPOSAL

When the demonstration is complete, the solutions may be rinsed down the drain with water.

HOW IT WORKS

The chemical reaction in this demonstration is simple electrolysis of water:

The color change is a result of the pH shift accompanying electrolysis acting on the pH indicators, which were selected to produce the desired colors. The anode is located in the center beaker, where water is oxidized to produce oxygen gas. Hydrogen ions are produced, decreasing the pH.

2 H₂O(l) → O₂(g) + 4 H⁺(aq) + 4 e^-

Cathodes are located on either side of the anode. In these beakers, water is reduced to form hydrogen gas:

4 H₂O(l) + 4 e^- → 2 H₂(g) + 4 OH^-(aq)

The reaction produces hydroxide ions, which increase the pH.

OTHER PATRIOTIC CHEM DEMOS

Red, White and Blue Density Column
Colored Fireworks Demonstration
Fireworks in a Glass - Safe Demo for Kids

REFERENCES

B. Z. Shakhashiri, 1992, Chemical Demonstrations: A Handbook for Teachers of Chemistry, vol. 4, pp. 170-173.
R. C. Weast, Ed., CRC Handbook of Chemistry and Physics, 66th ed., p. D-148, CRC Press: Boca Raton, FL (1985).

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How to Make Red Cabbage pH Indicator

Author
by Anne Marie Helmenstine, Ph.D.

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.

INTRODUCTION TO THE CABBAGE PH INDICATOR

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).

MATERIALS YOU WILL NEED

• Red cabbage
• Blender or knife
• Boiling water
• Filter paper (coffee filters work well)
• One large glass beaker or another 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. 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.)

1. 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.)
2. 3) Pour about 50 - 100 mL of your red cabbage indicator into each 250 mL beaker.
3. 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

For further details log on website :
https://www.thoughtco.com/making-red-cabbage-ph-indicator-603650

How To Make a Fruit Battery

Use Fruit to Generate Electricity for a Light Bulb

Author
by Anne Marie Helmenstine, Ph.D.

If you have fruit, a couple of nails, and wire then you can generate electricity to turn on a light bulb. Learn how to make a fruit battery. It's fun, safe, and easy.

HERE'S WHAT YOU NEED

• 1) citrus fruit (e.g., lemon, lime, orange, grapefruit)
• 2) copper nail, screw or wire (about 2" or 5 cm long)
• 3) zinc nail or screw or galvanized nail (about 2" or 5 cm long)
• 4) holiday light with 2" or 5 cm leads (enough wire to connect it to the nails)

MAKE A FRUIT BATTERY

1. 1) Set the fruit on a table and gently roll it around to soften it up. You want the juice to be flowing inside the fruit without breaking its skin. Alternatively, you can squeeze the fruit with your hands.
2. 2) Insert the zinc and copper nails into the fruit so that they are about 2" or 5 cm apart. You don't want them to be touching each other. Avoid puncturing through the end of the fruit.
3. 3) Remove enough insulation from the leads of the light (about 1") so that you can wrap one lead around the zinc nail and one lead around the copper nail. If you like, you can use electrical tape or alligator clips to keep the wire from falling off the nails.
4. 4) When you connect the second nail, the light will turn on!

HOW A LEMON BATTERY WORKS

Here's the science and chemical reactions describing a lemon battery. It applies to other fruits or vegetables you can try, too.

1) The copper and zinc metal act as positive and negative battery terminals.

2) The zinc metal reacts with the acidic lemon juice (mostly from citric acid) to produce zinc ions (Zn²⁺) and electrons (2 e^-). The zinc ions goes into solution in the lemon juice while the electrons remain on the metal.

3) The wires of the small light bulb are electrical conductors. When they are used to connect the copper and zinc, the electrons that have built up on the zinc flow into the wire. The flow of electrons is current or electricity. It's what powers small electronics or lights a light bulb.

4) Eventually, the electrons make it to the copper. If the electrons didn't go any further, they'd eventually build up so that there wouldn't be a potential difference between the zinc and the copper. If this happened, the flow of electricity would stop. However, that doesn't happen because the copper is in contact with the lemon.

5) The electrons accumulating on the copper terminal react with hydrogen ions (H⁺) that are floating free in the acidic juice to form hydrogen atoms. The hydrogen atoms bond to each other to form hydrogen gas.

LEARN MORE

• Citrus fruits are acidic, which helps their juice to conduct electricity. What other fruits and vegetables might you try that would work as batteries?
  
  
• If you have a multi-meter, you can measure the current produced by the battery. Compare the effectiveness of different types of fruit. See what happens as you change the distance between the nails.
  
  
• Do acidic fruits always work better? Measure the pH (acidity) of the fruit juice and compare that with the current through the wires or brightness of the light bulb.

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https://www.thoughtco.com/how-to-make-a-fruit-battery-605970

Science and technology on fast forward

Science and technology feed off of one another, propelling both forward. Scientific knowledge allows us to build new technologies, which often allow us to make new observations about the world, which, in turn, allow us to build even more scientific knowledge, which then inspires another technology … and so on. As an example, we'll start with a single scientific idea and trace its applications and impact through several different fields of science and technology, from the discovery of electrons in the 1800s to modern forensics and DNA fingerprinting …

From cathodes to crystallography

A cathode ray tube from the early 1900s

We pick up our story in the late 1800s with a bit of technology that no one much understood at the time, but which was poised to change the face of science: the cathode ray tube (node A in the diagram below). This was a sealed glass tube emptied of almost all air — but when an electric current was passed through the tube, it no longer seemed empty. Rays of eerie light shot across the tube. In 1897, physicists would discover that these cathode rays were actually streams of electrons (B). The discovery of the electron would, in turn, lead to the discovery of the atomic nucleus in 1910 (C). On the technological front, the cathode ray tube would slowly evolve into the television (which is constructed from a cathode ray tube with the electron beam deflected in ways that produce an image on a screen) and, eventually, into many sorts of image monitors (D and E). But that's not all …

In 1895, the German physicist Wilhem Roentgen noticed that his cathode ray tube seemed to be producing some other sort of ray in addition to the lights inside the tube. These new rays were invisible but caused a screen in his laboratory to light up. He tried to block the rays, but they passed right through paper, copper, and aluminum, but not lead. And not bone. Roentgen noticed that the rays revealed the faint shadow of the bones in his hand! Roentgen had discovered X-rays, a form of electromagnetic radiation (F). This discovery would, of course, shortly lead to the invention of the X-ray machine (G), which would in turn, evolve into the CT scan machine (H) — both of which would become essential to non-invasive medical diagnoses. And the CT scanner itself would soon be adopted by other branches of science — for neurological research, archaeology, and paleontology, in which CT scans are used to study the interiors of fossils (I). Additionally, the discovery of X-rays would eventually lead to the development of X-ray telescopes to detect radiation emitted by objects in deep space (J). And these telescopes would, in turn, shed light on black holes, supernovas, and the origins of the universe (K). But that's not all … The discovery of X-rays also pointed William and William Bragg (a father-son team) in 1913 and 1914 to the idea that X-rays could be used to figure out the arrangements of atoms in a crystal (L). This works a bit like trying to figure out the size and shape of a building based on the shadow it casts: you can work backwards from the shape of the shadow to make a guess at the building's dimensions. When X-rays are passed through a crystal, some of the X-rays are bent or spread out (i.e., diffracted) by the atoms in the crystal. You can then extrapolate backwards from the locations of the deflected X-rays to figure out the relative locations of the crystal atoms. This technique is known as X-ray crystallography, and it has profoundly influenced the course of science by providing snapshots of molecular structures. Perhaps most notably, Rosalind Franklin used X-ray crystallography to help uncover the structure of the key molecule of life: DNA. In 1952, Franklin, like James Watson and Francis Crick, was working on the structure of DNA — but from a different angle. Franklin was painstakingly producing diffracted images of DNA, while Watson and Crick were trying out different structures using tinker-toy models of the component molecules. In fact, Franklin had already proposed a double helical form for the molecule when, in 1953, a colleague showed Franklin's most telling image to Watson. That picture convinced Watson and Crick that the molecule was a double helix and pointed to the arrangement of atoms within that helix. Over the next few weeks, the famous pair would use their models to correctly work out the chemical details of DNA (M). The impact of the discovery of DNA's structure on scientific research, medicine, agriculture, conservation, and other social issues has been wide-ranging — so much so, that it is difficult to pick out which threads of influence to follow. To choose just one, understanding the structure of DNA (along with many other inputs) eventually allowed biologists to develop a quick and easy method for copying very small amounts of DNA, known as PCR — the polymerase chain reaction (N). This technique (developed in the 1980s), in turn, allowed the development of DNA fingerprinting technologies, which have become an important part of modern criminal investigations (O).

As shown by the flowchart above, scientific knowledge (like the discovery of X-rays) and technologies (like the invention of PCR) are deeply interwoven and feed off one another. In this case, tracing the influence of a single technology, the cathode ray tube, over the course of a century has taken us on a journey spanning ancient fossils, supernovas, the invention of television, the atomic nucleus, and DNA fingerprinting. And even this complex network is incomplete. Understanding DNA's structure, for example, led to many more advances besides just the development of PCR. And similarly, the invention of the CT scanner relied on much more scientific knowledge than just an understanding of how X-ray machines work. Scientific knowledge and technology form a maze of connections in which every idea is connected to every other idea through a winding path.

For further details log on website :
http://undsci.berkeley.edu/article/0_0_0/whathassciencedone_03

Shaping Scientists

We are all influenced by the cultures in which we grew up and the societies in which we live. Those cultures shape our expectations, values, beliefs, and goals. Scientists, too, are shaped by their cultures and societies, which in turn, influence their work. For example, a scientist may refuse to participate in certain sorts of research because it conflicts with his or her beliefs or values, as in the case of Joseph Rotblat, a Polish-born physicist, whose personal convictions profoundly influenced the research he undertook.

Top: Rotblat (back row, furthest to the right) attended and helped organize the first Pugwash Conference in 1957. It was a meeting of scholars and prominent figures with the goal of reducing the danger of armed conflict and seeking cooperative solutions for global problems. Bottom: Rotblat remained committed to the ideals of the Pugwash Conference and can be seen here (standing center) at the 54th conference in 2004. In 1939, Joseph Rotblat became one of the first scientists to grasp the implications of splitting atoms — that the energy they release could be used to start a chain reaction, culminating in a massive release of energy — in other words, an atomic bomb. However, instead of being excited by the possibility, Rotblat worried about the enormous cost to human life such weapons would have and avoided following up on the idea. Then, in the same year, Rotblat narrowly made it out of Poland before the Nazi invasion and eventually lost his wife to the German occupation there. He was now fearful that Germany would develop their own atomic bomb.Reasoning that a competing power with a similar weapon could deter Hitler from using such a bomb, Rotblat began working on the idea in earnest and came to the United States to help the Manhattan Project develop an atomic bomb. But then came another turning point. In 1944, Rotblat learned that German scientists had abandoned their research into atomic weapons. It no longer seemed likely that the bomb which Rotblat was helping to develop would be used merely for deterrent purposes. In 1944, Rotblat became the only scientist to resign from the Manhattan Project — because he found its probable application unethical. After World War II, Rotblat channeled his physics towards medical applications and in 1995 won the Nobel Peace Prize for his efforts towards nuclear nonproliferation.

Richard Levins Rotblat avoided a particular research area because of his ethical views; other scientists have chosen research topics based on their values or political commitments. For example, Harvard scientist Richard Levins was an ardent supporter of socialism. After a stint as a farmer and labor organizer in Puerto Rico, Levins returned to the U.S. to study zoology, but not to focus on a small-scale concern, like the behavior of an individual organism or species. Instead, Levins invested himself in population biology and community-level interactions — areas with implications for issues he cares about: economic development, agriculture, and public health. Levins' political views don't change the outcomes of his scientific studies, but they do profoundly influence what topics he chooses to study in the first place.

And of course, the societal biases that individual scientists may have influence the course of science in many ways — as demonstrated by the example below …

		FINDING INSPIRATION IN THE DETAILS Henrietta Leavitt Women at work at the Harvard College Observatory in 1891. Edward Pickering is standing in the corner to the left. In the early 1900s, American society did not expect women to have careers, let alone run scientific studies. Hence, women who chose to pursue science were frequently relegated to more tedious and rote tasks. Such was the case when Henrietta Leavitt went to work at Harvard College Observatory for Edward Pickering. She was assigned the task of painstakingly cataloguing and comparing photos of thousands of stars — mere specks of light. (In fact, at the time, women were preferred for such tasks because of their supposedly patient temperaments.) However, even within this drudgery, Leavitt found inspiration — and a startling pattern in her stars. For stars whose brightness varies — called variable stars — the length of time between their brightest and dimmest points is related to their overall brightness: slower cycling stars are more luminous. Her discovery had far-reaching implications and would soon allow astronomers to measure the size of our galaxy and to show that the universe is expanding. But Pickering did not allow Leavitt to follow up on this discovery. Instead, she was sent back to her measurements, as was deemed appropriate for a woman at that time, and the study of variable stars was left for other scientists to pick up. Had society's views of women been more open-minded, this chapter in astronomy's history might have played out quite differently!

For further details logon website :
http://undsci.berkeley.edu/article/0_0_0/scienceandsociety_04

Summing up science and society

In this section, we've seen that society shapes the path of science in many different ways. Society helps determine how its resources are deployed to fund scientific work, encouraging some sorts of research and discouraging others. Similarly, scientists are directly influenced by the interests and needs of society and often direct their research towards topics that will serve society. And at the most basic level, society shapes scientists' expectations, values, beliefs, and goals — all of which factor into the questions they choose to pursue and how they investigate those questions.

		GET INVOLVEDEven if you don't spend your days sequencing DNA, conducting particle accelerator experiments, or analyzing the composition of rocks, you can still influence the path of science with your actions every day. How? Here are some suggestions for getting more involved with scientific research: Change how funding agencies distribute research funds. For example, if you wanted to encourage research into alternative energy sources, you could write your congressperson to let him or her know what research you'd like to see government agencies fund. Support research. For example, if you wanted science to find a cure for juvenile diabetes, you could support a foundation that promotes research on the disease. Help with data collection and analysis. Some scientific research projects are actively seeking your help as a volunteer. For example, during your home computer's downtime, you could offer up its computing power to chemists at Stanford to help perform calculations about protein shapes. Or you could help astronomers by making backyard observations of variable stars. For more information about getting involved with scientific research through volunteering, check out organizations like DistributedComputing.info and Citizen Science.

Here, we've seen how society influences science. But what about the reverse? How does science influence society? To find out, read on …

For further details log on website :
http://undsci.berkeley.edu/article/0_0_0/scienceandsociety_05