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.

Food Colour Frenzy

We have had great fun with food colours and microscope slides recently reproducing an experiment with Dancing Droplets described by Nate Cira, Adrien Benusiglio and Manu Prakash. They posted a movie on Vimeo showing how to do it “Dancing Droplets: How to easily recreate the phenomena at home“.

We took up their invitation to have a go and found that red food colour was the best at pushing droplets of other food colours around.

Get out of my tube!

The Power of Red!

Here’s our movie posted on You Tube ‘Red Peril’ Food Dye, from which the above gif animation was constructed.

More details about the phenomena discovered by Nate Cira can be found on Scientific American “2 Common Liquids Spontaneously Form Dancing Droplets“.

More efforts from us (sorry about the wobbly camera work):

Our first success

Our first success

Twins

Twins

The Big Red

The Big Red


Can you see a heart?

Can you see a heart?


You might decide to have a go for yourselves. We found using an automatic micropipette (200 microlitres) speeds up the procedure considerably and increases the likelihood of success.

More fun with luminol

We recently carried out a reaction with luminol dissolved in sucrose solution.

Luminol reaction in a measuring cylinder

Luminol reaction in a measuring cylinder


The idea was that by dissolving the luminol reaction mixture in a concentrated sucrose solution we could carry it out in the bottom of a measuring cylinder and ‘float’ a solution containing copper (II) ions and iron (II) ions above it. The experiment worked quite well and a short movie clip can be viewed here.
After a few seconds

After a few seconds

The details of how we carried out the experiment are shown below
How we did it

How we did it

Take care, by the time its all over it can get fairly messy as the images show below.
Lights on, lights off

Lights on, lights off

Almost over

Almost over

Another fine mess...

Another fine mess…


Here’s an image of our first experiment done on a smaller scale (approximately one tenth) using 0.025g luminol and in a 20ml measuring cylinder.
On a smaller scale

On a smaller scale


Thanks to Chris Kruger and Jonathan Barton in developing this experiment.

We hope you have fun with luminol too!

Answers to the “Bicarb rockets” questions last time:
1. sodium hydrogen carbonate + ethanoic acid -> sodium ethanoate + water + carbon dioxide
NaHCO3 + CH3COOH -> CH3COONa + H2O + CO2

2. f = ma
The carbon dioxide produced by the chemical reaction builds up inside the bottle and when the bung finally comes out the gas pressure forces the liquid out of the bottle quickly. It is the force of the liquid moving downwards which pushes the bottle upwards.

Bicarb rockets

Bicarb rockets are fun to make and launch.

Lift off!

Lift off!

We use 150 ml vinegar and 3.5g sodium bicarbonate in a 600 ml plastic bottle. It’s easy to make a bicarb rocket if you have a rubber bung which tightly fits into the top of the bottle. We use a tripod to launch from as shown below and can easily reach a height of a three storey building using these materials.

The rocket building materials

The rocket building materials

The rocket, a 600ml water bottle

The rocket, a 600ml water bottle

Vinegar (dilute ethanoic acid)

Vinegar (dilute ethanoic acid)

Sodium bicarbonate (sodium hydrogen carbonate)

Sodium bicarbonate
(sodium hydrogen carbonate)

The bicarb is wrapped in paper towel to produce a small pellet

The bicarb is wrapped in paper towel to produce a small pellet

Do this outside!

Do this outside!

Countdown

Countdown

5, 4, 3, 2,...

5, 4, 3, 2,…

Here are some .gif animations of various bicarb rocket flights. Most of them were recorded at 240 fps (frames per second) using a Casio EX-FH100 camera.

A whole flight in frame

A whole flight in frame

A little closer

A little closer

Closer still

Closer still

CIMG9875_010

Too close – do you want vinegar on that!

Hit the roof

Hit the roof

How high can you go?

How high can you go?

Viewed from above (shot at 120 fps)

Viewed from above (shot at 120 fps)

Questions (answers next time)

1. What are the word and balanced symbol equations for this chemical reaction?

2. What is it that actually propels the rocket upwards?

“Propane Rockets”

SAFETY FIRST: This demonstration must be done with care and adequate ear protection must be worn by all present, along with safety spectacles. The use of commercial ear protectors are advised.

A propane rocket

A propane rocket


One demonstration that can be used to show how the ratio of reacting gas volumes relates directly to mole quantities in a balanced chemical equation is with a “propane rocket”.

In the experiments described below we used bottled gas, or LPG, which contains a mixture of propane and butane, in a 600 ml plastic bottle. Oxygen was also required. When ready to launch the bottle rocket was suspended from a fishing line using two paper clips and two rubber bands.

Fuelled and ready to launch

Fuelled and ready to launch

The balanced equations for the complete combustion of propane and butane are shown below.
Equations for the complete combustion of propane and butane

Equations for the complete combustion of propane and butane

Thus, it can be seen from the first equation that 5 volumes of oxygen are required to completely burn 1 volume of propane.

The gases are introduced into the bottle rocket by displacing water as shown. It is recommended that a fresh plastic bottle is used each time.

Oxygen from a gas syringe

Oxygen from a gas syringe

Followed by LPG

Followed by LPG


When the gases are used in the proportion of 5 volumes of oxygen to 1 volume of bottled gas, a very loud explosion propels the bottle at speed across the laboratory.
Complete combustion.. BANG!

Complete combustion.. BANG!

Reduce the proportion of oxygen and incomplete combustion occurs. By trial and error a slower flying rocket can be obtained.

With 3 to 4 volumes of oxygen : 1 volume of propane a slower rocket results

With 3 to 4 volumes of oxygen : 1 volume of propane a slower rocket results

However, if the proportion of oxygen is reduced too far the rocket will fail to launch.

Too much fuel, not enough oxygen - disaster!

Too much fuel, not enough oxygen – disaster!

All of the above .gif animations were produced from high speed movies shot at 120 fps (frames per second). Here is another animation produced from a movie shot at 1000fps

High speed movie 1000fps

High speed movie 1000fps

Frame by frame

Frame by frame

Thus, the effect of varying the molar ratio of the two reacting gases, using reacting gas volumes, can be shown.

Match head rockets

Match head rockets are fun to make.

For safety we use no more than four match heads.

We have lift off

We have lift off

There are many videos on You Tube describing how to make these rockets.

Here’s how we do it:

About 15 x 10 cm

About 15 x 10 cm

But trial and error is involved

But trial and error is involved

Roll smoothly

Roll smoothly

and tightly

and tightly

This is the rocket body

This is the rocket body

Making way for the fuel

Making way for the fuel

No more than four

No more than four

Don't worry if the solid crumbles

Don’t worry if the solid crumbles off

Experiment with a mixture of crumbles and whole match heads

Experiment with a mixture of crumbles and whole match heads

Don't let the stick fall out whilst loading

Don’t let the stick fall out whilst loading

Use a second stick as a ram rod

Use a second stick as a ram rod

This tail is probably a little too short

This tail is probably a little too short

The pin forms part of the launch pad

The pin forms part of the launch pad

Wrap tightly to form an exhaust tube

Wrap tightly to form an exhaust tube

You can twist the foil too

You can twist the foil too

Make sure the pin moves in and out smoothly

Make sure the pin moves in and out smoothly

This is going to roll up

This is going to roll up

Like a party toy or tube of toothpaste

Like a party toy or tube of toothpaste

Squash the end as tightly as you can

Squash the end as tightly as you can

Pliers do work

Pliers do work

But so does biting down with your teeth

But so does biting down with your teeth

All systems go

All systems go

You can vary the angle easily by pushing the end of the pin into Plasticene

You can vary the angle easily by pushing the end of the pin into Plasticene

The launch – Wear eye protection and stand well back

This one seemed to have too many whole match heads which shot out of the rocket quite spectacularly

This one seemed to have too many whole match heads which shot out of the rocket quite spectacularly

Here are three more animations of another successful launch.

Students were not allowed to hold the Bunsen burner as shown.

Teachers do so at their own risk, but they must wear gloves and a full face mask if they do.

Crumbled up match head solid fuel seems to burn more smoothly

Crumbled up match head solid fuel seems to burn more smoothly

They can sometimes fly several metres

They can sometimes fly several metres

MUST WEAR GLOVES (unlike here)

MUST WEAR GLOVES (unlike here)

The squashed and rolled up aluminium foil unwinds on launch and is puffed out

The squashed and rolled up aluminium foil unwinds on launch and is puffed out

Launch pad failure

Launch pad failure

Launch pad failures are quite common and seem to occur particularly when the nose is not flattened tightly enough during manufacture or when a hole is made in the foil.

Answers to two chemical reactions last time

Equations for the reactions are:

iron + sulfur   –>  iron sulfide

Fe  +  S   –>   FeS

and

copper (II) oxide  +  carbon   –>   copper  +  carbon dioxide

2 CuO   +   C    –>   2 Cu   +   CO2

Both reactions give out a lot of heat and this can be seen by the intense glow which continues even when the external heat source is taken away.  Reactions which give out heat like this are called exothermic reactions.

Here are some pictures of the products.  First the iron sulfide:

We had to smash the test-tube to get the product out of this one

We had to smash the test-tube to get the product out of this one

Unfortunately, it was still attracted to a magnet, typically due to unreacted iron filings

Unfortunately, it was still attracted to a magnet, typically due to unreacted iron filings

The fused lump of product probably consists of iron sulfide plus unreacted iron filings and some sulfur

The fused lump of product probably consists of iron sulfide plus unreacted iron filings and some sulfur

Here is the product of the thermal reduction of copper (II) oxide with carbon:

Brown coloured copper metal is produced

Brown coloured copper metal is produced

 

 

Two chemical reactions

Two chemical reactions often done at school are the reaction of iron filings with sulphur and the reduction of copper (II) oxide with carbon. Answers to the questions posed below will be given in the next blog.

1. The reaction of iron filings with sulphur

Iron filings and sulphur

Iron filings and sulphur

The reaction is hot!

The reaction is hot!

How can you tell that the reaction produces a lot of heat?

What is the name of the product?  Will it be magnetic like the iron filings?

The product of the reaction

The product of the reaction

2. The reduction of copper (II) oxide with carbon

A mixture of copper (II) oxide and carbon

A mixture of copper (II) oxide and carbon

Mini volcano!

Mini volcano!

How can you tell that the reaction produces a lot of heat?

What are the products of this reaction? What will the contents of the test-tube look like when it has cooled down?

What is the new brown coloured material?

What is the new brown coloured material?

Two exothermic reactions often carried out in school.

Can you write equations for these two reactions?

Fun with luminol

Luminol is a chemical frequently used to produce blue light by chemiluminescence.

One classic demonstration uses luminol in a reaction carried out as it spirals down a length of tubing such as the one shown here:

Chemiluminescence, courtesy of Nigel Evans, Bloxham School.

Chemiluminescence, courtesy of Nigel Evans, Bloxham School.

Another demonstration uses luminol in a spray to detect fake ‘blood spatter’ such as is often seen in TV forensic science dramas. In our school chemistry club we used a recipe published by Anne Marie Helmenstine on About.com This recipe requires two solutions which are mixed together in equal proportions shortly before use. Solution 1 – Luminol stock solution (2 g luminol + 15 g potassium hydroxide + 250 mL water). Solution 2 – 3% hydrogen peroxide in water (our local pharmacy supplied a 6% hydrogen peroxide solution which needed to be diluted by half with water). However, because this mixture uses a fairly concentrated solution of potassium hydroxide, which is corrosive, it must be used in a fume cupboard. Under such conditions we were unable to see much of a glow when sprayed onto test paper ‘painted’ with an iron (III) chloride solution.

We had much more fun by pouring the luminol mixture into a Petri dish in a darkened room. We then added 0.1M iron (III) chloride and 0.1M copper (II) sulfate using dropping pipettes. In this way more students were able to investigate this exciting reaction for themselves:

Luminol reaction in a Petri dish

Luminol reaction in a Petri dish

In another similar experiment we tried electrolysing the reaction mixture using graphite electrodes and 9v from a power pack:

Electrolysing the luminol reaction

Electrolysing the luminol reaction

You too might have some fun if you try this. Happy Halloween from our Chemistry Club.