Category Archives: Experiments

Clinical trials and reports: a petition

Just a quickie today. Please go and sign this petition: All Trials Registered.

Around half of all clinical trials have not been published; some trials have not even been registered. If action is not taken urgently, information on what was done and what was found in trials could be lost forever, leading to bad treatment decisions, missed opportunities for good medicine, and trials being repeated unnecessarily.

This is one of Ben Goldacre‘s pet projects, and it’s crucial.  In his words: “Positive findings are around twice as likely to be published as negative findings. This is a cancer at the core of evidence-based medicine.”

Find out a little more about why this is so important here.

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Lightning has an electromagnetic personality

In the late 1700s, Charles Augustin Coulomb put the snap, crackle and pop from a number of perilous experiments together and deduced the form of the electrostatic force law. Here’s what he found:

  1. You can’t tell just by looking at an object whether or not it carries a charge. Unless you’re an X-Man. Possibly.
  2. There are only two types of charge: positive and negative. Opposites attract, as the old cliché goes. And an object with equal amounts of each is electrically neutral, like Switzerland.
  3. All normal matter contains electric charge (except Findus lasagnes, which are not yet understood by science).Electrons may be transferred from one object to another.
  4. In an isolated system, the total electric charge is always conserved. So when you rub a balloon on a cat, no charge is created – electrons are simply redistributed between the cat and the balloon (and anger is created in the cat. Cats are often not subject to the usual laws of physics. Mine can teleport). Charge has its very own law of conservation.
  5. Because of the attraction between unlike charges, any item with a deficit of electrons (which has, therefore, a positive charge) will attract negatively charged items. But that’s not all: it will also pull in any electrons that happen to be hanging around. That’s how electric currents work, in the very simplest terms. Put a negative thing next to a positive thing, and electrons will flow from one to the other until they’re sharing them equally.

Fun facts about electric charge

  1. A small plastic troll doll with purple hair. Looks like it's been introduced to a Van der Graaf generator.

    Me. On a Monday.

    If you super-dry your hair then give it a vigorous brushing, you can make it stand on end. I often don’t need to put this much effort in; my barnet’s natural state appears to be one resembling those little trolls. 

  2. You can stick balloons to the ceiling using electrons, thus defying the laws of gravity. This is an interesting demonstration of the difference in strength between the electrostatic force and the gravitational force. Relatively speaking, the electrostatic force is MUCH stronger. Mind-bogglingly so. (Although you can’t really compare them, because they are fundamentally different things with arbitrary units of measurement.
  3. If you’re wearing nylon clothes, and you take them off in a dark room, you can sometimes see sparks as the separation of the clothing from your skin causes the air around you to undergo electrical breakdown. You can dismantle the air, like an X-Man. Possibly.
  4. Electrostatic charges are responsible for lightning. (More below.)

One of my favourite things is finding out that an everyday (but brilliant) phenomenon is still not fully understood by our biggest brains. We really don’t understand how lightning works! Partly because experiments are bloody dangerous…

A scientist named Georg Wilhelm Richmann, a German physicist living in Russia, was killed during a lightning experiment in 1753. He has the dubious honour of being the first person killed during an experiment involving electricity.

He was electrocuted in St Petersburg while “trying to quantify the response of an insulated rod to a nearby storm”. Any excuse to duck out of a meeting, even back then: he dashed off on hearing the news of a thunderstorm, taking his engraver with him to record the event for posterity.

During the experiment, and somewhat predictably (with the benefit of hindsight), he was struck by lightning. (It’s said that it was ball lightning, a very rare phenomenon that wasn’t believed to exist until the 1960s.)

The explosion that followed blew up his shoes, singed his clothes and knocked him dead. That wasn’t the end of his scientific exploits, however; his body was dissected to find out what effect his terminal experiment had on his organs.

We don’t understand lightning

Lightning is probably the most dramatic and well-known natural phenomenon resulting from electrical charge. But how does it work? Well, here’s what we know:

  • On humid days, rising air currents carry water vapour up into the atmosphere.
  • This occurs in giant clouds – they’re around 10km thick.
  • The water droplets cool as they rise, then freeze to form hailstones. Hailstones are required for lightning to occur.
  • The hailstones grow as more water condenses on them, then begin to fall under gravity when they become obese.
  • As they fall, they tend to melt and emerge from the cloud as heavy rain.
  • Lightning flashes develop near the base of a cloud, and are caused by the separation of positive and negative charges within the cloud.
  • The electrical activity occurs at an altitude where the temperature is between 0°C and -10°C – the only temperature range in which both hailstones and supercooled water drops can exist simultaneously.

Beyond these facts, we’re not really sure of anything!

We all know what lightning looks like, but this video shows a whole plethora of beautiful phenomena set to the strains of Robert Miles epic tune ‘Children’. One of the soundtracks to my messy youth.

Theorising about lightning

Most of the theories about the origins of lightning are based on a transfer of charge between the rising water drops and the falling hailstones. This leaves the water drops with a net positive charge and the hailstones with a net negative charge.

With the water drops pulled to the top of the cloud by rising air currents, and the negatively charged hailstones falling under gravity, the result is a net excess positive charge near the top of the cloud and a net negative charge near the bottom.

The tops of clouds are happy. The bottoms are angry.

Diagram illustrating the charge distribution in a thundercloud.

This process increases until the electrostatic charges are so large that one of two things (may) happen:

  1. The vapour in the cloud undergoes electrical breakdown, allowing the electrons to flow up through the cloud in a giant spark of lightning – a ‘cloud flash’.
  2. The air beneath the cloud suffers electrical breakdown and the negative charge at the bottom flows to the positively charged ground as forked lightning.

As I said, though, the charging mechanism is not really understood. The middle of a thundercloud is a bit of a hairy place to be, so there are not many experiments documented. I quite fancy making some kind of protective bubble and mooching into a cloud. If anybody would like to fund this hare-brained scheme, do drop me a line. You could be in line to share a Nobel Prize, you never know…

Why I love science

Or, at least, this is one of the reasons I love science…

Take a look at this article in Nature. It’s interesting, yes – especially if you understand anything of quantum gases. But it’s the comments that made me laugh!

The article also underlines our everyday misunderstanding of and misuse of terms such as ‘temperature’ and ‘heat’.

Dive in!

Nature article

Science also invites respectful, light-hearted banter. Compare this to the trolling and abuse you often see in the comments sections of blogs and YouTube…

The science of mouldy soup

TMA04

I must start this blog post with a bit of a “hurrah!” I have received my mark for TMA04 (Book 4: Chemistry). Drum roll… I got 92% – even with the “discussion” about one of the questions, and its ludicrous wording and requirements.

So, I’m very chuffed indeed. I understand chemistry. Or at least, I understand the basics, which will stand me in good stead for Book 5: Life – and, I hope, level two of my journey.

Mould

Activity 2.1 of Book 5 required me to investigate fungal particles in the air. In my kitchen, to be precise. So an experiment was undertaken. Bear with me… it’s aces.

The aim of this investigation was to estimate the density of fungal particles (spores) in the kitchen by exposing an appropriate growth medium (Sainsbury’s Basics tomato soup – I’m a cheapskate!) to a known volume of air, and then seeing how many fungi grow on it.

Equipment

Small can of Sainsbury’s Basics tomato soup

Rectangular plastic container

Paper and sticky tape to label container

Cling film

Ruler.

Experimental design

The container needs to be wide enough and deep enough to accommodate the soup, plus a reasonable volume of air. About half a litre should be plenty. A rectangular container will make it easier to measure and calculate the volume of air under the cling film.

By washing the container thoroughly, and drying it upside down, the likelihood of contamination will be reduced. To ensure that nothing else gets inside, the soup will be transferred to the container quickly, and then immediately covered with clingfilm. A second layer of clingfilm will be used to make the container airtight, thus preventing anything else entering the container.

The volume of air can be measured by multiplying together the length and width of the container, and then multiplying by the depth of air from the clingfilm to the surface of the soup.

It should be kept out of reach of children and animals, and where it is unlikely to be disturbed. Although I can’t imagine anyone – husband or cats – would look at that and think: “Ooh yum! I’m a bit peckish” and then dive right in…

How long should I leave it? Well, how long’s a piece of string? That will depend on how quickly mould forms on the soup. A week or so should be fine.

I will record the start and finish date and time, and record when fungus first begins to appear, and when it stops increasing.

What should I do with the container and its contents afterwards? Well, the OU recommends that I throw away the whole shebang – for health and safety reasons (excuse me while I stop laughing); however, I will dispose of the mouldy soup in the toilet, rinse the container into the toilet, then put it through the dishwasher for a thorough wash. I am not throwing away a perfectly good Tupperware container! That’s going to have my lunch in it tomorrow.

Practical procedure

The container was thoroughly washed and left upside down to dry. When it was dry, the can of soup was opened and quickly poured into the container. The soup was immediately

covered with two layers of clingfilm, and made airtight.

The experiment was labelled “Biohazard: not to be eaten”, and the date and time recorded

(May 31, 2011 at 7.30pm). The container

was placed out of the reach of the cats, and left where it was unlikely to be disturbed.

Biohazard: mouldy soup

The volume of air in the container was measured:

Depth from clingfilm to surface of soup: 3.0 cm

Width of container: 13.5 cm

Length of container: 18.5 cm

Volume    = 3.0 cm x 13.5 cm x 18.5 cm

= 749.25 cm3

= 7.5 x 10-4 m3 (2 significant figures) Note: the corners of the container were rounded, so this figure is approximate.

The first mould began to appear on June 4 and were tiny white spots (about 1 mm in diameter), mostly around the edges of the tub.

On June 5, the white spots had grown to a diameter of around 3 mm to 4 mm, with 1 mm green/blue patches in places. More areas of growth had appeared. Condensation also appeared on the clingfilm, which made observations a little awkward.

My mould was respiring! I was so proud. My very own baby mould; they grow up so fast.

By June 9, no more spots were appearing. And it’s probably a good thing, because it was getting a little crowded in there, and the patches were beginning to fight among themselves. I did NOT want to have to step in there and break anything up.

Results

The Mould Boyz

Seventeen separate areas of mould were counted. Most of the mould was clinging to the edges of the soup on the container, with a few patches in the centre. The patches in the centre resembled blisters lying just on or beneath the surface. They were milky in appearance, and slightly jelly-like, measuring 0.5 cm to 1.0 cm in diameter. Delicious.

The patches around the edge were either white, or white with green/blue areas. The white patches had stalks, while the green/blue mould was furry in texture. These patches measured around 1.5 cm to 2.5 cm across. I’ve seen this furry mould before; it normally inhabits the bit of sandwich you’ve just put into your mouth. You know this, because there’s half a patch of mould left when you look at your meal.

Analysis of results

Each area of growth probably represents one fungus, which arose from one fungal spore. My result was: 17 fungal spores per 7.5 x 10-4 m3 air.

To find the number of fungal spores per cubic metre of air:

= fungal spores per m3

= 2.3 x 104 fungal spores m-3 (2 significant figures)

I could work out the total number of fungal spores in the air in my whole kitchen; but frankly, I’d rather not know! I’m quite happily living in blissful ignorance, and perpetuating the dastardly rumour that I am, in fact, a great wife who cooks, cleans, maintains her rather great bottom AND makes interesting conversation that does not involve mould.

Critical thinking

The density of fungal spores I obtained is almost certainly an underestimate of the true density. This does not make me happy. I thought 22,666 spores per cubic metre was quite alarming enough.

Assumptions were made that the number of fungal spores in the air are evenly distributed throughout the room; this is unlikely to be the case, especially with movement of air. It may be that not all the spores trapped in the container grew into patches of mould. It was also assumed that all spores had grown into mould when I ended the experiment; this may not be the case.

Further investigations

We were supposed to think about what else we could investigate. But really, the only thing that came to mind was the mating habits of fungus. I suspect I’ve been staring at a screen for too long…

My next activity involves researching Leontopithecus rosalia. Stay tuned!

The nature of acids, and a long string of hydrocarbons

I am charging through Book 4: The Right Chemistry, and after a shaky start, I’m enjoying it very much.

I LOVE organic chemistry. The regular nature of molecular structures pleases me greatly. And I get to make a mess.

Last week I undertook an experiment to measure the acidity or otherwise of common household substances. It was just like being back at school, and I got to Make A Mess in the kitchen. Win!

I tested washing up liquid, shampoo, stain remover, laundry powder, tonic water, cranberry juice, bleach, tap water – and resisted the urge to plunder the house for anything that could have a Universal Indicator paper stuck into it. Including the cats.

I was very surprised at how acidic tonic water is – it has a pH of 3. So, what is pH?

pH stands for “potential hydrogen”. I didn’t know that, and don’t remember being told at school (although it is entirely possible that I was setting fire to a bunsen burner at the time). This makes sense, however, as I now also know that the pH is a convenient way of describing what a substance’s hydrogen ion concentration is.

So, tonic water has a pH of 3, which means that its hydrogen ion concentration is about 1.0 x 10¯³ mol dm¯³. Handy. Saves using lots of very small numbers and scientific notation.

Acids yield hydrogen ions when they are dissolved in water – so the higher the concentration of hydrogen ions, the more acidic the substance. Bases yield hydroxide ions: so the more hydroxide ions contained in a solution, the more basic that solution is.

The strength of an acid is determined by how far it dissociates in solution – hydrochloric acid, for example, is a strong acid because it dissociates almost completely. Almost all the HCl molecues dissociate to give positive hydrogen and negative chloride ions; whereas vinegar (acetic acid – or ethanoic acid, to give it its proper name) is a very weak acid as it only partially dissociates in solution.

The book then took us through the method of calculating a substance’s pH from its hydrogen ion concentration – or vice versa. And very simple it is too. I can imagine it will come in very useful to you all on a daily basis – if for no other reason than to impress people in the pub.

“See that pint? It has a pH of 4.5, which means it has a hydrogen ion concentration of 0.0000316 mol dm¯³.”

Anyway. I’m pleased with my progress, and have moved onto hydrocarbons. Which are pretty cool.

I am a long string of hydrocarbons. As are you. And so is almost everything, in fact. Including crude oil.

Hydrocarbons are subdivided into alkanes and aromatics. Alkanes are further subdivided into linear-chain alkanes, branched-chain alkanes, and cycloalkanes. This are all pretty good descriptions of their molecular structures.

Carbon has a valency of four, meaning that it can hang onto four other atoms. Hydrogen has a valency of one, so it can only hang onto one other atom. Linear-chain alkanes are long strings of carbon atoms attached to a maximum of two other carbon atoms, and two or three hydrogen atoms. These alkanes can also be folded over; they needn’t be long, straight strings.

Branched-chain alkanes are similar to linear-chain alkanes, but instead of having two hydrogens, a carbon atom will be attached to a third carbon, forming a “branch”. Hence the name.

And cycloalkanes are rings of carbon atoms, with hydrogen atoms attached. These, too, can have branches.

Aromatics are also rings of carbon atoms, but some of them have double bonds, and some of them single bonds.

All this is useful for grading petrol, believe it or not. When you’re filling up your vehicle, the unleaded nozzles have “95” or “97” printed on them. These are the octane numbers; and the higher the octane number, the better the performance of the petrol. Y’see, linear-chain alkanes don’t make very good motor fuel – they burn unevenly, and cause the engine to “knock” (small explosions interrupting the burn). Branched-chain and cycloalkanes are much better; and if you can add an aromatic to the mix, then it’s better still.

I’m not sure why yet; I’ll get back to you when I’ve found out.

I’m particularly enjoying hydrocarbons as I get to draw molecular structures. This pleases me: they are very regular, and appeal to my sense of neatness. This is ethane:

And this is an aromatic – napthalene – note the double bonds, and pleasant circular structure:

I’ve downloaded a chemistry drawing package to use for my Tutor Marked Assignment. I’ll see how I get on with that…

I’m looking forward to Book 5: Life – and am hoping it will give me more of an idea of my future studying direction. I love everything so far – but I think a focused four-directional future will be time-consuming to say the least…

An experiment to investigate light in the style of a pirate

I have had a lovely weekend in the sunshine, much of which has been spent outside in our garden, under the beautiful cherry tree, on our new garden furniture. I’ve been pottering around, weeding the vegetables, planting more seeds, and watching the cats chase motes of dust.

In between, I’ve been studying hard – book 3, Energy and Light. I’m almost there; I’ve completed most of TMA03; all I needed to do was Activity 11.1 – Investigating Light.

Joe and I liberated a cardboard document box from his offices, and I planned my experiment. It is set out below, just as it is in my folder (with perhaps just one or two embellishments, and an extra instructive illustration). Some of the details have been changed and the first-person voice has been used because the write up was part of the assessment, and so cannot be made public for fear someone may plagiarise me. So some of this may or may not be true!

Investigating light: determining the wavelengths of spectral lines from an energy-saving light bulb.

Equipment

  • Diffraction grating (300 lines per mm)
  • Tungsten filament light bulb (40 W)
  • Energy-saving light bulb (11 W)
  • Lovely stripy table lamp (for the tungsten bulb)
  • Tall standard lamp (for the energy-saving bulb)
  • Large cardboard document box
  • Pieces of Amazon book cardboard
  • Gaffer tape
  • Sharp knife
  • Paper protractor
  • Blu-Tack
  • Black cotton thread
  • Red drawing pin
  • Dressmaker’s pin
  • Eye-patch
  • Table
  • Dressing gown

Abstract

An experimental measurement of the angles of diffraction of blue, green and red spectral lines from an energy-saving light bulb was undertaken using a diffraction grating, a protractor, and household items. The wavelengths of each spectral line were calculated. The value obtained for the blue spectral line was 450 nm; the value obtained for the green spectral line was 550 nm; the value obtained for the red spectral line was 600 nm (all to two significant figures).

Aim

To determine the wavelengths of blue, green and red spectral lines from an energy-saving light bulb.

Method

Having liberated the box from Joe’s work in a ninja-style midnight operation, I cut a thin slit in it using the sharp knife. Joe took this off me, and did it properly with a minimum of blood spilled. I tidied the edges using gaffer tape. Gaffer tape can do anything: FACT. The table lamp containing the tungsten bulb was placed within, and Amazon cardboard was cobbled around the edges, in an attempt to prevent too much light from escaping and having a party where my spectral lines were supposed to be.

I had a gander through the diffraction grating, and this is what I saw – a continuous spectrum:

This is an actual photograph I took *proud*

Professional pirate dark-room. Eye patch provided.

Next, I needed to take a look at the spectrum produced by the energy-saving bulb. So I undid my gaffer-taped masterpiece, and fumbled the floor lamp with the energy-saving bulb under there. I couldn’t quite manage to see the spectrum this time, so I created a dark-room, thus:

This created the ideal conditions to observe and photograph my diffraction spectrum – which was not continuous, and was in fact a line spectrum. Again, I photographed it:

Line spectra from an energy-saving bulb

All this was very pretty, but had to be interrupted by a trip to Charlie’s to make me a longbow. You see, my marvellous husband (he of the fabulous presents) bought me A Big Piece of Wood for my birthday. Not just any piece of wood, mind; a piece of yew, laminated with maple and lemon wood. He, Charlie and I began the shaping of a (very) long bow. It’s going to be grand!

Back to science.

Later, when darkness had fallen, I continued my experiment and set up my equipment. Leaving the box with the energy-saving bulb where it was, I stuck it down to prevent any disastrous movement, and placed a paper protractor about 50cm away. A drawing pin pierced the protractor, to provide an anchor point for the thread. The diffraction grating was placed upon the protractor at the axis. Thread was tied to the drawing pin and the dressmaker’s pin, and all was ready. See:

Experimental set up.

This is where the eye-patch comes in. To measure the angle of diffraction for each spectral line, you have to line up the spectral line itself with the line on the grating and the thread upon the protractor. This is to be done with one eye, to prevent parallax error. I found myself unable to do this, and so had to use an eye patch.

Of course, it naturally followed that I had to conduct the rest of the experiment in the manner of a pirate. Grog was acquired, and duly consumed. Tables were swabbed, angles were swashed, and the thread was buckled. Much like my knees.

The experiment was a success! The wavelength of the blue, green and red spectral lines from the energy-saving light bulb were calculated as: 450 nm,  550 nm and 600 nm respectively. This isn’t far off the actual wavelengths of light emitted by an energy-saving light bulb. Go and google it if you don’t believe me.

This has been Science, by Vicky. I’ve enjoyed it; all that remains to be seen is how well my tutor likes the write-up… I do think that the eye patch was relevant. And the dressing gown.

On evaporation and blissful motion

I am three quarters of the way through my two week precipitation experiment, which I have mostly been very good about recording. I totally forgot last night, which is a bit piss poor, to be honest. And my only excuse is that I was knackered. Oh, and we had to tighten the chain on my motorbike, which was the flappiest, crappiest thing ever. I’ve ordered a new one, and sprockets, because it’s pretty FUBAR’d.

Anyway – tonight’s precipitation was more interesting than of late; it’s been raining quite a lot, with the Met Office predicting floods because the ground is pretty saturated after the snow.

Vessel A (no funnel) now contains 20mm of water.

Vessel B (funnel) now contains 30mm of water. I also noted that the underside of the funnel was liberally coated with condensation. It’s been pretty breezy and dry today, so I am thinking that much of the water from vessel A upped and left. Either that, or my neighbours are playing silly buggers with my experiment (although it doesn’t smell of wee, so I should be thankful for that, I guess).

Evaporation interests me. I know how it happens, and why, but it still seems sort of magical. All that water contained in the air – a little like something into nothing. I love clouds too. Especially when viewed from above, because they look so solidly soft and inviting. I always find it difficult to believe that I would just plummet to a pancakey death, when it looks like I should be able to roll around in them…

But I digress. Evaporation and precipitation massively influence our planet’s climate, and temperatures. Water vapour is the most abundant greenhouse gas of all – I always assumed it was carbon dioxide. Clouds are a pretty efficient way to move all that water around. I also like to think of all the water that ever was just being shuffled around in different forms. A little like energy – it’s not created or destroyed, just changed.

So the experiment is almost over. I’m not sure how accurate my measurements have been – but I don’t think that’s the point. I think they want us to really think about experimental design, and observation, which I think I have done. I’ve enjoyed it, in a “back at school” kind of way. I’m already looking forward to the next one!

Blissful motion

For the first time in ages, I really enjoyed my journey to work this morning. I remembered why I love my motorbike. The freedom it engenders; the thrill and the beauty of the ride. It was much warmer and drier, and I flowed through bends and past imprisoned people half asleep in their boxes. It was just bliss.

Writing

I know some people who can write. I mean really write. They’re very good, and often very funny. I’m a little envious. Not too envious though – because they actually spend time doing it. I always think I want to, but never quite do. I have ideas, but don’t write them down (ha!) and I do my thinking on the bike, or somewhere equally unsuited to making notes. And my memory is pants.

I must do better. And I must do more reading!