Whoosh brothers

The whoosh bottle demonstration involves setting light to methanol vapour in a thick walled 20L water bottle. By adding a few drops of water into the methanol, salts such as LiCl, NaCl and KCl can be incorporated into the ignition mixture and add colour to the resulting flame.

Here are some images of the same.

First three pictures of the experiments:

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Lithium whoosh – the bottle on the right did not ignite.

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Sodium whoosh – only the middle one

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Potassium whoosh

Next are three animated gifs of the experiments:

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What colour do you see in the flame in the bottle? Is it the characteristic flame colour from Li, Na or K?

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Tried for a triple whoosh, but only the middle one worked. Was it Li, Na or K?

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Better colours with the lights out? It’s usually difficult to see the colour of the flame with this shy violet. Li, Na or K?

The whoosh brothers! A composite gif animation of all the above.

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Whoosh brothers!

Try as I might I could not get more than one bottle to ignite at a time. Movies uploaded to You Tube soon.

 

SAFETY

Follow appropriate safety guidelines when igniting the bottles. Methanol vapour is toxic. Only use thick walled plastic bottles. Do not try more than one ignition per bottle. Wash each bottle by filling completely with cold water after each ‘burn’. Our laboratory was ventilated with the all the windows open after the each experiment for more than an hour.

Flatlines

Ice to steam or I can sing a heating curve.

Can you identify the songs?

Here are some karaoke lyrics to substitute in for songs on stages of the heating curve for ice to steam (temperature against time).

Stage 1 – Song 1

“Temp low, sweet ice a lot

All the vibrations are slow

Add heat, start warming up

Vibrations mean the ice is going to go”

Stage 1 – Song 2

“Ice picking up good vibrations

Heat giving it excitations” repeat

Stage 2 – Song 3

“At nought degree C, I want to break free

To break free from your bonds takes energy

Molecules, use heat to break free”

Stage 3 – Song 4

“All the molecules liquid now

All the molecules move around

Molecules keep on moving round all night long

Heat it up, heat it up, baby heat it up

na na na na na na na na 

Temperature going up, going up, water getting hot”

Stage 4 – Song 5

“I am boiling, I am boiling

Steam again, breaking free

I am boiling, no more bonding

Temperature constant, 100 degrees C”

Stage 5 – ???

 

 

Phase change flatlines

A New Year’s Eve Chemistry Karaoke challenge. Examine the picture below which shows a heating curve for ice through to steam. The challenge is to come up with karaoke lyrics to popular songs of your choice which fit the regions on the curve 1 to 5 describing the behaviour of the water molecules. Students often have difficulty in explaining why the temperature does not increase during the regions of the curve representing phase changes; solid ice to liquid water (2.) and liquid water to gaseous steam (4.). Thus, the added challenge is to explain the reasons for these ‘flatlines’ in your karaoke lyrics.

20151231200458

 

 

 

Magnesio

Magnesio is magnesium in Spanish. We cut out a small figure in magnesium metal and stuck a little manganese (IV) oxide to its arms and head using Superglue.

OLYMPUS DIGITAL CAMERA

Magnesio

We then dropped the figure into a luminol reaction mixture set-up in a measuring cylinder containing layers of sucrose solutions as described in March 2015. It needed a little prodding with a glass rod to get it to submerge at first, but then started bobbing up and down as shown in the animated .gifs below.

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The luminol reaction mixture is in the sucrose layer between 15 – 60 ml

The bottom layer of sucrose solution solution contained some 4M hydrochloric acid so that when the magnesium sank down that far, it reacted with the acid producing bubbles of hydrogen, causing it to float up again.

When the magnesium rose up into the topmost layer, which was 0.5M iron (III) chloride, it probably got coated with the dark green iron containing precipitate formed there, which may have helped it to sink again.

The middle of the measuring cylinder contained the luminol reaction mixture, (potassium hydroxide, luminol and 6% hydrogen peroxide solution).2015_11_21_magnesio_01_20

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Blue bubble ghost?

2015_11_21_Magnesio_03_202015_11_21_Magnesio_04_202015_11_21_Magnesio_05_20.gif

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No, it’s Magnesio!

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Finally, when the luminol reaction was over, Magnesio was washed out into the sink.

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Luminol all used up, where’s Magnesio?

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There he is, in the sink!

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Relaxing after a swim on a paper towel

Maybe you will be able to see a Magnesio adventure soon.

See the movie file on You Tube

The three metals attracted to the neodymium magnet last time were nickel, cobalt and iron.

 

 

Magnetic attraction

Nickel (II) salts, like nickel (II) sulfate, are classed as category 1 carcinogens and colbalt (II) salts, like cobalt (II) chloride, are category 2 carcinogens. As such, neither of these two kinds of salts are recommended for use in experiments at school.

Setting up

Setting up

What follows is a description of some displacement reactions which were carried out on a microscale in order to minimise the hazards like the ones mentioned above. The experiments involved adding magnesium ribbon to small volumes of aqueous solutions of some transition metal salts.

Small pieces of magnesium ribbon were dropped into approximately 1.5ml of each of the following solutions:

1M manganese (II) sulfate
0.5M iron (II) chloride
1M cobalt (II) chloride
1M nickel (II) sulfate
0.5M copper (II) sulfate
and
0.5M zinc sulfate.

After several minutes a small neodymium magnet was waved over the magnesium metal strips. The results are summarised in the gif animations below.

Microscale displacement reactions using magnesium

Microscale displacement reactions using magnesium

Zinc and copper

Zinc and copper

Manganese and iron

Manganese and iron

Nickel and cobalt

Nickel and cobalt

The animations were constructed from a movie of the reactions which can be viewed on You Tube here.

Which pieces of magnesium were attracted to the neodymium magnet and why?

All the colours of a tomato

Toxic cocktail - tomato juice with a splash of bromine water

Toxic cocktail – tomato juice with a splash of bromine water

Lycopene is the molecule responsible for much of the red colour of tomatoes.

The conjugated double bonds absorb certain wavelengths of light

The conjugated double bonds absorb certain wavelengths of light

When bromine water is added to tomato juice, various addition reactions occur, with bromine molecules reacting with some of the double bonds in the lycopene molecules.

The wavelengths of light absorbed by the brominated products probably depends on the number of conjugated double bonds remaining, i.e. not reacted with bromine. In any case, many different colours are seen ranging from yellow to green and blue.

Here’s an animation of one such experiment. First bromine water is added to tomato juice in a measuring cylinder and then the mixture is stirred with a glass rod.

Re-colourising tomato juice

Re-colourising tomato juice

Almost a rainbow!

The brominated tomato juice shows various colours.

The brominated tomato juice shows a variety of colours.

We also wanted tp see what happened when chlorine water and tincture of iodine were added to tomato juice.

Before adding the halogens

Before adding the halogens

After adding the halogens to tomato juice

After adding the halogens to tomato juice

In close-up

Chlorine water + tomato juice close-up

Chlorine water + tomato juice close-up

Bromine water + tomato juice close-up

Bromine water + tomato juice close-up

Tincture of iodine added to tomato juice close-up; outside in bright sunlight

Tincture of iodine added to tomato juice close-up; outside in bright sunlight

Unsurprisingly, the chlorine water bleached the tomato juice white, whilst the tincture of iodine produced some interesting, if quite dark, green and blue colours after some time.

In summary, some interesting colours were seen in the tomato juice, although these demonstration experiments must be carried out in a fume cupboard. They can lead onto a discussion of addition reactions in alkenes and a test for alkenes, such as ethene, by decolourising bromine water.

Index & Contents 07/12 to 07/15

Index & Contents – July 2012 to July 2015

To go to a post in the contents list below, click on the relevant month in the Archives list on the right hand side of the page.

July 2015
PALT
A holiday quiz where nearly all of the answers are Al (aluminium) or Pt (platinum).
A .gif animation is shown of an experiment where aluminium and platinum foils were introduced into a blue Bunsen burner flame side by side.

June 2015
Rust on a melon
We showed numerous pictures and .gif animations for some oxidation and reduction reactions involving iron. In summary the reactions were:
Oxidation
1. Rusting of iron nails, including a .gif animation of nails in an experiment lasting three and a half weeks investigating the factors necessary for rust formation.
2. Burning sparklers, including a .gif animation.
3. Speeding up the burning of iron wool by whirling it around on the end of a length of string (.gif animation).
Reduction
4. A thermit reaction carried out at night over a water melon, including a .gif animation.

May 2015
Balls of fire
We described a rapid, small scale method for making nitrocellulose without producing large amounts of waste. We experimented with using potassium carbonate, lithium carbonate, limewater (calcium hydroxide) and barium carbonate in place of sodium hydrogencarbonate to neutralise the acid reaction mixture. As a result, nitrocelluloses were produced which gave different burning characteristics and flame colours.
Ten .gif animations are shown, one each at normal speed and one in slow motion for sodium, potassium, lithium, barium and calcium impregnated nitrocelluloses.

April 2015
Food colour frenzy
We repeated the dancing droplets of food colour reported by Nate Cira, Adrien Benusiglio and Manu Prakash. Five .gif animations are shown of the droplets moving on microscope slides. We found that red food colour was best at pushing around all the other colours. We also posted a movie ‘Red Peril’ Food Dye which can be viewed here: https://www.youtube.com/watch?v=IKY-Zqa7R10

March 2015
More fun with luminol
We describe a novel way of showcasing the classic luminol chemiluminescent reaction by carrying it out in a dense layer of sucrose solution at the bottom of a measuring cylinder, which also contained hydrogen peroxide. A second less dense layer of sucrose is layered on top of this mixture and serves as a barrier to a third top layer which contained iron (III) chloride and copper (II) sufate solutions. The reaction was started by dropping a small piece of lead metal dipped in manganese dioxide powder into the measuring cylinder.

The oxygen bubbles produced by the decomposition of the hydrogen peroxide rise up the measuring cylinder and are surrounded by blue lighht from the luminol reaction.
A movie of the reaction can be viewed here: https://www.youtube.com/watch?v=mt8EX4pZuJU&feature=youtu.be

February 2015
Bicarb rockets
Numerous pictures and seven .gif animations of Bicarbonate Rockets, which are often made at school. These rockets are constructed from plastic bottles and fuelled with a reaction mixture of vinegar and sodium bicarbonate. The two reactants produce carbon dioxide gas, but it is the force of the liquid reaction mixture blown out of the bottom of the bottle by the carbon dioxide which provides most of the upward lift. The most critical design feature for our rockets was finding a plastic bottle with a neck of just the right size diameter to match our medium sized rubber bungs.

January 2015
Propane rockets
Numerous pictures and four .gif animations of Propane Rockets made using a plastic bottle and a mixture of oxygen and bottled gas. These can be used to illustrate stoichiometry and balanced chemical equations when studying chemistry at school.
Details of the .gif animations are as follows; three (normal speed) .gif animations showing:
1. Complete combustion of the fuel (enough oxygen) and a very fast rocket.
2. Incomplete combustion (not enough oxygen) and a slow moving rocket.
3. Incomplete combustion (not enough oxygen) and failure to launch.
The fourth .gif animation is a slow motion animation constructed from a high speed movie shot at 1000 frames per second. It shows the fuel burning down the bottle as the rocket takes off.

December 2014
Match head rockets
Numerous pictures and four .gif animations on how we make our Match Head Rockets in Chemistry Club.
Also, three pictures and a .gif animation showing the products of the two experiments featured in the November 2014 post.

November 2014
Two exothermic chemical reactions commonly carried out at school
1. Iron and sulfur
A .gif animation and other pictures are shown for the reaction which takes place when a mixture of iron filings and sulfur are heated together in a test-tube. Iron sulfide is produced.
2. Copper (II) oxide and carbon
A .gif animation and other pictures are shown for the reaction which takes place when a mixture of copper (II) oxide and carbon are heated together in a test-tube. A thermal reduction takes place leading to the formation of copper metal.

October 2014
Fun with luminol
Variations on the classic demonstration reaction utilising the chemiluminescence of luminol.
In one experiment the luminol reaction mixture was poured into a Petri dish and drops of iron (III) chloride and copper (II) sufate solutions were dropped into it using pipettes. Flashes of light were produced around the droplets as they fell into the reaction mixture.
In a second experiment the luminol reaction mixture was again poured into a Petri dish, drops of iron (III) chloride and copper (II) sufate were added and then the mixture was electrolysed using carbon electrodes and a 9 volt power supply.
A .gif animation is shown for each of these two experiments.

September 2014
Strawberry blonde
Demonstrating the bleaching effect of hydrogen peroxide solution using strawberries and the effect of temperature on the rate of these reactions.
Includes:
A .gif animation of a frozen strawberry warming up to room temperature next to a strawberry already at room temperature, (the former goes all squashy).
A .gif animation of a strawberry dropped into 6 vol hydrogen peroxide in a small beaker.
A .gif animation of a frozen strawberry and a room temperature strawberry dropped into beakers of hydrogen peroxide side by side.

August 2014
Unreactive metals
On the reactivity series of metals studied at GCSE level in chemistry and reactions of magnesium, zinc, iron and copper with 2M hydrochloric acid.
Includes a .gif animation showing the four metals reacting with 2M hydrochloric acid for approximately a minute, then a second .gif animation showing the reaction of an iron nail and a piece of copper foil with 2M hydrochloric acid over a period of a week.

July 2014
What does the word ‘salt’ mean?
On the two meanings of the word salt in chemistry at school.
A .gif animation showing the build up of a 3D digital image modelling the cubic shaped ionic lattice of sodium chloride.

June 2014
A celebration of IYCR, The International Year of Crystallography 2014
A lot of images of crystals of ionic compounds encountered by students at school, including thirteen .gif animations of crystals growing, as seen under a microscope.

The crystals shown in order of appearance are:
Sodium chloride
Sodium bromide
Sodium iodide
Potassium chloride
Potassium bromide
Potassium iodide
Ammonium sulfate
Magnesium sulfate
Copper (II) sulfate

May 2014
Flame tests
The colours seen in web images for flame tests vary.
There are .gif animations for lithium, sodium, potassium and calcium flame tests.

Alkali metals in water
A .gif animation of lithium, sodium and potassium metals added to a small bowl of water at the same time from a spatula.
Three .gif animations, one each for lithium, sodium and potassium metals, added to a small bowl of water individually.
A .gif animation showing lithium, then sodium, then potassium metals being added to a large trough of water sequentially.

April 2014
Great snakes!
When a mixture of sucrose (4 parts) and sodium bicarbonate (1 part) is doused with ethanol and set light to, trailing ‘snakes’ of dark grey ash emerge from the flames.
Includes a .gif animation of the experiment and another illustrating the artistic qualities of the ‘snakes’ produced.

March 2014
The chromatography of chlorophyll
Thin layer silica chromatography of a chlorophyll containing extract from grass. We used a 70:30 mixture of diethyl ether : petroleum ether (bp 60-80) as the eluting solvent. Includes numerous images of the procedure and a .gif animation of the elution of a TLC plate and pigment separation.

February 2014
Glowing things
On the u.v. fluorescence of quinine (from tonic water) and chlorophyll (from spinach). The .gif animations show the following subjects illuminated by alternating u.v. light and fluorescent light.
A .gif animation of jelly made with and without the addition of tonic water in plastic cups.
A .gif animation showing the red colour of spinach juice.
A .gif animation showing a ‘spooky vampire smiley face’ fashioned from jelly made with tonic water and spinach juice.

January 2014
Snow from brine
Making ‘snow scenes’ from cardboard soaked in saturated sodium chloride solution spiked with a few drops of potassium hexacyanoferrate (II)

Modelling a sodium chloride crystal
A .gif animation showing a rotating model of the sodium chloride crystal lattice, made from brightly coloured modelling clay.

December 2013
Rudolf the red-nosed boiling tube
A Christmas themed Santa’s challenge experiment, involving the reaction of sodium hydrogencarbonate and calcium carbonate with hydrochloric acid.

Belousov–Zhabotinsky reactions
.gif animations of B/Z reactions in a beaker (one animation) and in Petri dishes (five animations)

November 2013
High speed photography and .gif animation of the explosive reaction between hydrogen and oxygen bubbles and a high speed .gif animation of the hydrogen “pop” test.

October 2013
Halloween Chemistry 2
Pictures showing the use of fluorescent inks extracted from highlighter pens in a Halloween themed display under u.v. light.

Hydrogen chloride and ammonia diffusion experiment
A .gif animation showing the diffusion of hydrogen chloride and ammonia gases which react to form a ‘white smoke’ of ammonium chloride in a glass tube. In the experiment we used a temperature probe to show the exothermic nature of the reaction.

September 2013
A .gif animation showing the explosion produced when a mixture of hydrogen and oxygen bubbles are lit with a burning wooden splint.
A .gif animation using Lewis diagrams to illustrate the balanced equation for the reaction between hydrogen and fluorine.
A .gif animation showing the diffusion of hydrogen chloride and ammonia gases in a glass tube and reacting to produce ‘white smoke’ of solid ammonium chloride.

August 2013
When hydrogen met fluorine, including a .gif animation showing bond formation in a molecule of hydrogen fluoride.

July 2013
Explaining the results seen in the halogen/halide displacement reactions June 2013 .gif animation. Chlorine displaces bromide ions and iodide ions from solution. Bromine displaces iodide ions from solution.

June 2013
Halogen/halide displacement reactions in aqueous solution
A .gif animation showing iodine, bromine and chlorine added to NaCl, NaBr and KI.

Fluorite
Two .gif animations, one illustrating the formula of calcium fluoride (fluorite) and a second showing the fluorescence of fluorite under u.v. light.

May 2013
Testing for chlorine
A .gif animation of the bleaching effect of chlorine on some orange flowers.
A .gif animation showing chlorine gas bleaching red and blue litmus paper.

April 2013
Testing for carbon dioxide
A .gif animation of an experiment illustrating the thermal decomposition of copper (II) carbonate and testing the carbon dioxide gas produced by bubbling it through limewater
A .gif animation showing a large carbon dioxide bubble bursting and extinguishing six burning candles placed around it.

March 2013
Testing for hydrogen and oxygen gases
Three .gif animations of test-tube reactions; testing for hydrogen gas with a burning wooden splint, testing for hydrogen with a hot piece of platinum foil and testing for oxygen with a glowing wooden splint.

Testing for water using cobalt (II) chloride
A .gif animation of cobalt chloride paper used in testing for water; blue when wet (hydrated), pink when dry (dehydrated). Cobalt (II) chloride is also sometimes used as an indicator in the silica gel drying agent used in desiccators, but it is toxic.

February 2013
Testing for water using copper (II) sulfate
A .gif animation of a simple dehydration experiment heating hydrated copper (II) sulfate in a test-tube with a Bunsen burner and then adding water to it.

January 2013
The colours of copper (II) chloride, copper (II) nitrate and copper (II) sulfate crystals in pictures, a laboratory desiccator and its effect on hydrated aluminium sulfate over time.

December 2012
Coloured crystals to illustrate the “Halloween Chemistry” poem, fake blood, green copper (II) chloride in a Santa illustration, wet lithium chloride crystals and a silver bearded wolf’s head

November 2012
The shapes of large NaCl, NaBr, NaI crystals in pictures

October 2012
“Halloween Chemistry” poem, KCl, KBr, KI crystals in one picture

September 2012
Periodicity

August 2012
The Periodic Table, lithium fluoride and sodium chloride

July 2012
Ionic bonding and the sodium chloride lattice

Palt

A summer holiday quiz with only two* answers

1. The symbols of two commonly encountered metals can be formed from the first four letters of platinum. What are the symbols and names of the two metals?

2. Only one of these metals oxidises readily in a Bunsen burner flame, which one?

Aluminium and platinum foils in a Bunsen burner flame - which is which?

Aluminium and platinum foils in a Bunsen burner flame – which is which?

3. The words flammable and inflammable mean the same thing, which is, ‘burns easily’. Which of the two metals is highly flammable/inflammable when in powdered form?

4. Which of the two metals is used in the Thermite or Thermit reaction? Hint, see last months blog.

5. Which of the two metals is very abundant in the Earth’s crust and is produced in millions of tonnes annually?

6. Which of the two metals is relatively unreactive and placed at the bottom of the reactivity series of metals at GCSE?

7. One of the two metals is a precious metal and is used in making jewelry. Which one?

8. Which of the two metals is used to make an important anticancer drug? Hint, the drug is called cisplatin.

9. Which of the two metals is an important catalyst in many chemical reactions and can be used in catalytic converters in cars?

10. Which metal derives its name from the Spanish word for silver, plata?

11. Of the two metals, give the symbol of the metal with (a) “nium” at the end of its name and (b) “num” at the end of its name? This question may prove more difficult for Americans.

12. Which rare-earth metal could be an alternative answer for one of the metals in question 1?

*Well, three including the answer to question 12.

Answers
1. Pt, platinum & Al, aluminium
2. Al
3. Al
4. Al
5. Al
6. Pt
7. Pt
8. Pt
9. Pt
10. Pt
11 a) Al, b) Pt
12. La, lanthanum

Rust on a melon

Never go back to a lit melon!

Never go back to a lit melon!

We make a lot of things out of iron, usually in the form of mild steel and one of the major problems with it is that it rusts. Unless the object is protected in some way, the iron reacts with oxygen and water around it to make the hydrated form of iron (III) oxide.

iron + oxygen + water -> hydrated iron (III) oxide

Rust is hydrated iron (III) oxide and is seen as the orange-brown solid that forms on the surface of the steel.

At school we often carry out an experiment with nails to illustrate the factors involved in rusting.

Nails used in a rusting experiment

Nails used in a rusting experiment

Here is an example of one such experiment:
Four nails under different conditions

Four nails under different conditions

When left for three and a half weeks this is what was observed:
Which nail rusted the fastest?

Which nail rusted the fastest?

The nail that rusted fastest was the one with both oxygen and water present.

More Oxidation reactions of iron

Iron oxidises rather more quickly when iron filings are sprinkled in a Bunsen burner flame as shown here.

Sprinkling iron filings in a Bunsen burner flame

Sprinkling iron filings in a Bunsen burner flame

This sparkling affect, as the iron filings burn, is exploited in the production of commercial Sparklers

Sparkle, sparkle

Sparkle, sparkle

The jagged patterns produced by the burning iron particles are appealing

Close-up of the pretty crinkly pattern produced by a burning sparkler

Close-up of the pretty crinkly pattern produced by a burning sparkler

Iron wool also burns quite dramatically when ignited and swung around on a piece of string.

Have a care that doesn't drop in your hair!

Have a care that doesn’t drop in your hair!

Iron forms more than one oxide during these reactions, but it is the orange-brown iron (III) oxide which is most stable and widespread around us. For example, sand is sand coloured due to contamination of the quartz with this iron oxide, otherwise it would likely appear white.

What gives sand its sandy colour?

What gives sand its sandy colour?

Reversing the process

Vast quantities of iron oxides are mined and the iron is extracted from them. This is done by heating iron oxide with carbon in a Blast furnce. A reduction reaction takes place as the carbon takes the oxygen away from the iron.

But perhaps the most dramatic reaction of getting the iron out of iron (III) oxide at school is seen when carrying out a Thermit reaction.

iron (III) oxide + aluminium -> iron + aluminium oxide

Here aluminium takes the oxygen away from iron as it is the more reactive of the two metals.

To illustrate the spectacular nature of the Thermit reaction we decided to carry it out at night over a watermelon.

Cut a cone shaped hole out of the top of a watermelon

Cut a cone shaped hole out of the top of a watermelon

Stick two wooden splints either side of the hole

Stick two wooden splints either side of the hole

Insert a filter paper cone to hold the Thermite mixture above the moist melon

Insert a filter paper cone to hold the Thermite mixture above the moist melon

Put 20g of Thermit mixture into the filter paper and then a magnesium fuse

Put 20g of Thermit mixture into the filter paper and then a magnesium fuse

A thermite reaction carried out over a watermelon

A thermite reaction carried out over a watermelon

Not all the mixture reacted

Not all the mixture reacted


Our example is not as awesome as the half a ton of Thermite Jamie Hyneman and Adam Savage used on a car in MythBusters, but it was quite pleasing nevertheless.

Next morning we examined the product. We found a lump of solid with metal in it inside the melon. It was attracted to a bar magnet, but did not appear to be pure iron.

Look what we found inside

Look what we found inside

Finally, answers to questions from last time.

The characteristic flame colours are sodium = yellow, potassium = lilac, lithium = red, calcium = orange-red.

I still haven’t found out why our nitrocellulose laced with barium produced a bright white flame, rather than green on burning.

Thanks to Jonathan Barton for help and encouragement in developing this work.

Balls of fire

Cotton wool balls are very easy to nitrate on a micro-scale and can provide a stimulating demonstration to support teaching chemistry at Advanced Level at school. Adding a mixture of concentrated nitric acid and concentrated sulfuric acid to cotton wool produces nitrocellulose and when dried this burns spectacularly. A bright yellow flame characteristic of the presence of sodium is evident.

Trained chemists only

Do not do this!

Teacher demonstration A method is described below for the nitration of cotton wool on a microscale which considerably reduces the risks involved and minimises the impact on the environment in terms of the quantities of chemicals used and amount of waste generated.

Microscale nitration of cotton wool

Microscale nitration of cotton wool

After allowing the nitrating mixture of concentrated nitric acid and concentrated sulfuric acid to react with the cotton wool for 20 to 30 minutes whilst sitting on ice, the reaction is terminated by washing the cotton wool with water and then sodium bicarbonate solution. The latter step neutralises any acids present. We decided to see what effect it would have on the product and its burning characteristics by varying the base used in the neutralisation step.

Accordingly, potassium carbonate, lithium carbonate, limewater (calcium hydroxide) and a barium carbonate slurry were each used in place of the sodium bicarbonate in a series of experiments. The results of burning the nitrocelluloses produced are shown in the animations below, with the nitrocellulose produced using a sodium bicarbonate wash shown first for comparison.

Nitrocellulose - sodium

Nitrocellulose – sodium

Nitrocellulose - sodium (from 1000fps movie)

Nitrocellulose – sodium (from 1000fps movie)

Nitrocellulose - lithium

Nitrocellulose – lithium

Nitrocellulose - lithium (from 1000fps movie)

Nitrocellulose – lithium (from 1000fps movie)

Nitrocellulose - calcium

Nitrocellulose – calcium

Nitrocellulose - calcium (from 1000fps movie)

Nitrocellulose – calcium (from 1000fps movie)

Nitrocellulose - barium

Nitrocellulose – barium

Nitrocellulose - barium (from 1000fps movie)

Nitrocellulose – barium (from 1000fps movie)

Nitrocellulose - potassium

Nitrocellulose – potassium

Nitrocellulose - potassium (from 1000fps movie)

Nitrocellulose – potassium (from 1000fps movie)

Two questions for chemistry students (answers next time)

1. What are the characteristic flame test colours produced by a) sodium, b) potassium, c) lithium and d) calcium?

2. Why does barium produce a bright white flame in the above images whilst its characteristic flame test colour is green?

Here are some links to the original movie files uploaded to You Tube from which the animations were constructed.

Burning nitrocellulose – sodium, filmed at 120fps

Burning nitrocellulose – sodium, filmed at 1000fps

Burning nitrocellulose – potassium, filmed at 120fps

Burning nitrocellulose – potassium filmed at 1000fps

Burning nitrocellulose – lithium, filmed at 120fps

Burning nitrocellulose – lithium, filmed at 1000fps

Burning nitrocellulose – calcium, filmed at 120fps

Burning nitrocellulose – calcium, filmed at 1000fps

Burning nitrocellulose – barium, filmed at 120fps

Burning nitrocellulose – barium, filmed at 1000fps

Finally, thanks to Tony Pluck for his help and encouragement in developing this work.