Chemistry Demonstrations List

Published: 2021-07-20 05:58:16
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Important Notice: All demos should be performed with appropriate personal protective equipment (PPE). These items could include goggles, gloves, aprons, and fume hoods; other needs will be discussed in demo description. Take careful note of warnings with each chemical used. These safety concerns should be discussed as part of your demonstration. Reminder: Use your own words and cite any references of information verbally during the demo. Consult instructor with any questions.

Dragons Breath

Topic: electron excitation, characteristic spectral lines

Equipment:

Candle taped to the end of a meter stick

Matches

Spray bottle which MUST be washed out after every session!!!!!

Bin of Empty capped bottles already labeled to store your solutions made 1st week (keep yours in your drawer)

PPE:

Gloves, goggles, fume hood

Chemicals:

50 mL ethanol (Danger! Highly flammable liquid and vapor. Harmful if swallowed. Causes skin irritation. Causes serious eye irritation. May cause drowsiness or dizziness. Suspected of damaging fertility or the unborn child. Causes damage to organs (central nervous system, optic nerve) (oral, dermal).),

7.5 mL water

1.5 g lithium chloride (DANGER! Harmful if swallowed. Causes skin irritation. Causes serious eye irritation.)

To perform: Make a mixture of 50 mL of ethanol, 7.5 mL of water and about 1.5 g of lithium chloride. Shake to dissolve as much lithium chloride as possible. Put the above solution in a spray bottle. Prime the bottle by spraying into the hood until a FINE mist is achieved. Hold a lit candle at arms length, poised over a drop cloth to collect dripped, melted wax mess, in the hood. Hold the spray bottle about 46 inches from the candle and quickly spray ethanol through the flame. This should produce a nice little fireball that lasts for a second. If the candle is put out by the spray, relight with tealight which should be already lit before the start of the demo.

Options: Use other salts instead of lithium chloride to produce different colored flames. Copper chloride (Warning-Irritant), for example, creates a blue-green flame.

Cleanup: Please store your ethanol solutions that you make in the first week in sealed and labeled bottles in your drawer (see the bin of labeled bottles for repeated use during the demo weeks, to finally be disposed of in ethanol Waste at the conclusion of the final demo. PLEASE: After each use of the spray bottles they should be thoroughly rinsed and pumped with water and left for the next set of students to use, before finishing each trial.

Safety: Perform this demo by holding the candle in the hood, and spraying into the hood. Ethanol sprayed in the flame is highly flammable and will produce a fireball, so ample precautions should be used to avoid conducting the experiment around potentially flammable items such as clothing, etc.

2. Elephants Toothpaste

Topic: catalysts, exothermic reactions, kinetics, decomposition

Equipment:

500 mL graduated cylinder (two if desired)

Tray to conduct experiment on for easy cleanup

PPE:

Gloves, goggles

Solutions:

30 mL of 30% hydrogen peroxide (Danger! Causes skin and serious eye damage, corrosion or irritation.)

Approximately 5 mL (a Loooong squirt) of dish washing detergent

3.0 g of potassium iodide (Warning! Harmful if swallowed. Causes skin irritation. Causes serious eye irritation.)

To Perform: Pour about 30 mL of hydrogen peroxide into the graduated cylinder, add a squirt of detergent and, when ready, add about 3.0 g of sodium iodide. Huge yellow worm springs out of cylinder!

What is happening: The hydrogen peroxide oxidizes the iodide ion to iodine, while simultaneously releasing oxygen gas. The gas is trapped in the detergent, creating foam.

Options: Drip food coloring down the sides of the graduated cylinder before adding the potassium iodide to make striped toothpaste, or add food coloring to hydrogen peroxide dish detergent solution before adding the potassium iodide to color the whole foam result.

Waste: Waste can be carried to the sink on the tray and rinsed down the drain.

Safety: This demo utilizes chemicals which can be corrosive to the skin and eyes. Gloves and goggles are therefore important to use.

3. Two Styrofoam experiments (should be combined)

Topic: polymers, are they soluble?

Styrofoam Cup

Chemicals and Equipment:

10 mL acetone (Danger! Highly flammable liquid and vapor. Causes serious eye irritation. May cause drowsiness or dizziness.) in a bottle, with small label

500 mL distilled water in juice bottle, with small label

4 new Styrofoam cups

PPE: goggles, gloves

To perform: Pour distilled water into cup and drink. Ask if someone else wants a nice strong drink and quickly pour half a cupful of acetone (you have 3 seconds before the bottom drops out! NOTE: hold the cup receiving the acetone over the large beaker to be used for part b), then continue with demo b

AND

Styrofoam Peanuts

Equipment:

Magnetic stirrer, with stirring bar

I L beaker

Bag of polystyrene packing chips

PPE: goggles, gloves

Chemicals:

100 mL of acetone (Danger! Highly flammable liquid and vapor. Cause serious eye irritation. May cause drowsiness or dizziness.)

To perform: Rapidly stir 100 mL of acetone in the 1 L beaker. As the foam chips are added, they rapidly dissolve. Students are usually amazed at the large volume of chips that can be reduced to a substantially smaller volume.

Waste: Discard solution in acetone waste

Safety: Ensure the magnetic stirrer used has the heat dial set to OFF Acetone is flammable.

4. The Methylene Blue Traffic Light

Topic: Concepts: reduction/oxidation or redox chemistry, Indicators

Equipment:

500 mL Florence flask with stopper to fit

PPE: gloves, goggles, apron

Chemicals:

300 mL distilled water

8 g potassium hydroxide (DANGER! Harmful if swallowed. Causes severe skin burns and eye damage.)

10 g dextrose (This chemical is considered nonhazardous according to GHS classifications for the Hazard Communication Standard.)

68 drops of methylene blue indicator (Not classified as having physical

or health hazards according to GHS)

To perform: Dissolve 8 g KOH in 300 mL distilled water in 500 mL Florence flask. Just prior to doing the demonstration, dissolve 10 g dextrose in the KOH solution and then add 68 drops of methylene blue solution. Swirl the flask and allow it to sit undisturbed until it becomes colorless (about one minute). To do the demonstration, give the flask a quick shake or two. The blue color appears again and then slowly fades. This process can be repeated many times.

What is happening: The oxygen present in the flask oxidizes the methylene blue dye to its blue form. The basic conditions cause the dextrose to reduce the methylene blue dye to its colorless form. Shaking the flask reintroduces more oxygen into the solution and re-oxidizes the methylene blue to its blue form, continuing the cycle until the oxygen in the flask is used up.

Waste: Please dispose of waste in labeled Methylene Blue Traffic Light Waste bottle.

5. Shaving Cream in a Vacuum

Topic: Boyles Law

Equipment:

Vacuum pump

Desiccator (Please take good care of this equipment, it is fragile and $expensive$! Ask for instructions on how to open and close safely)

Can of shaving cream

Plate

Vacuum hose.

PPE: goggles

To perform: To remove the lid on desiccator, carefully grasp securely and slide horizontally until the seal is released and the lid can be lifted. Set down lid gently. Put a generous daub of shaving cream on the plate, put plate on the white platform of the dessicator, VERY CAREFULLY HANDLE THE LID and GENTLY place and then slide to match lid to base, turn stopcock to open (holes match up), connect vacuum pump to dessicator with hose at stopcock and turn on pump. Open stopcock and watch shaving cream swell up and completely fill inside. Turn off vacuum before foam creates the undue mess; shaving cream into the stopcock and vacuum hose is a no-no, difficult to clean and if it gets far enough, bad for the pump.

What is happening: The shaving cream is full of gas bubbles in equilibrium with the gas pressure of the atmosphere pushing down on the bubbles. When the air is removed, the bubbles expand.

Waste: Waste can be discarded down the drain. Please be sure dessicator and plate are clean at the conclusion of the trial, again, handling the dessicator parts with great care! Thanks!

Safety: glassware under pressure is a safety hazard.

Various vacuum pumps will be capable of removing the varying amount of air from the jar, giving contradictory levels of vacuum. Stronger pumps will pull the near complete vacuum. Some base plates are made up of a gasket that gives enough seal. Other gadgets will need the application of grease to offer a complete seal between the bell jar and the base plate. While there are other pumps that are much stronger when they run that they are able to shift across the table. There are some of the vacuum cleaners that require to run them, which normally come with the pump or can be ordered as a part of the replacement.

6. The Breathalyzer

TOPIC Applied Electrochemistry, reduction/oxidation or "redox" chemistry

REFERENCE Chem 13 News, January 1979, p. 15

EQUIPMENT Test tube rack with 618 x 150 mm test tubes

PPE: gloves, goggles, apron, fume hood for breathalyzer solution preparation

CHEMICALS

Potassium dichromate (DANGER! May intensify fire; oxidizer. Toxic if swallowed. Harmful in contact with skin. Causes severe skin burns and eye damage. May cause an allergic skin reaction. Fatal if inhaled. May cause allergy or asthma symptoms or breathing difficulties if inhaled. May cause genetic defects. May cause cancer. May damage fertility or the unborn child. Causes damage to organs (kidneys, liver, Skin) through prolonged or repeated exposure.)

Sulfuric acid (DANGER! Causes severe skin burns and eye damage.)

Silver nitrate (Warning! Causes skin irritation. Causes serious eye irritation)

PROCEDURE 250 mL of breathalyzer solution (Danger! Corrosive) is made ahead of time. If sealed very well, the solution can be stored for over a year. The solution is identical to the solution formerly used by law enforcement officers and is made as follows:

Dissolve 6.25 g of potassium dichromate in 125 mL of distilled water. Slowly and carefully add 125 mL of concentrated sulfuric acid, small portions at a time, TO the above solution, in a flask surrounded by an ice bath. (CARE: The solution gets very hot and is extremely corrosive!) After the addition of acid is finished and the solution has cooled, add 10 mL of silver nitrate solution (2 g of silver nitrate dissolved in 10 mL of water).

To duplicate the police procedure, the reaction must take place at 50 3 0C, but the reaction actually works quite well at room temperature. To each test tube add 3-5 mL of breathalyzer solution and then add a few drops of each compound to be tested. If the compound is an alcohol, the yellow breathalyzer solution is rapidly oxidized to a green color. The quicker the color change and the darker the final green color, the more alcohol is present. Substances such as acetone or ethyl acetate will eventually cause a color change but they are much slower to react and can easily be distinguished from alcohols.

Some solutions to try:

ethanol (Danger! Highly flammable liquid and vapor. Harmful if swallowed. Causes skin irritation. Causes serious eye irritation. May cause drowsiness or dizziness. Suspected of damaging fertility or the unborn child. Causes damage to organs (central nervous system, optic nerve) (oral, dermal). 2propanol (isopropyl alcohol, i.e. rubbing alcohol, Danger! Flammable, Irritant) reacts very quickly

ethyl acetate (Danger! Highly flammable liquid and vapor. Causes serious eye irritation. May be harmful if inhaled. May cause drowsines...

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