Here's a trick that just looks impossible. Even when you know what's happening it just doesn't look right.
You'll need:
2 identical forks
Cocktail sticks or toothpicks
A glass
Matches
Safety:
Matches are involved so get adult supervisions.
What to do:
1. Lock the tines of the forks together.
2. Jam a cocktail stick through between the tines of the fork so that is sticks about 1 cm out the back.
3. Pick up the forks and place the cocktail stick over the rim of the glass with the handles pointing in towards the glass. Find the spot where the forks balance.
This already looks pretty amazing. But it gets better!
4. Now light the end of the toothpick thats pointing towards the inside of the glass.
So what's going on?
It just looks all wrong doesn't it? But the explanation is really quite simple. Half the weight of the forks is in front of the rim of the glass and the other half is behind the rim of the glass. So everything balances nicely. Sometimes physics just doesn't look right.
A bottle of hydrogen peroxide. You can get this from most pharmacists. Try and get 9%, but 6% will do.
Dried baker's yeast.
Washing up liquid.
An empty plastic bottle (500ml or so).
A glass with a 20ml of water in it.
A teaspoon.
Safety:
Hydrogen peroxide is a mild bleach (which is why its used to make your hair go blond). Be careful with it and don't get it in yours eyes. Best get some adult supervision for this one. And it makes a bit of a mess so do it outside.
What to do.
1. Put about 2 teaspoons of yeast into the glass with the water. Mix it about until it looks like brown muddy water.
2. Squirt about 2 teaspoons of washing-up liquid into the plastic bottle.
3. Pour 50ml of hydrogen peroxide onto the washing-up liquid.
4. Pour the yeasty water into the plastic bottle. Stand back and ...
What's going on?
Remember the chemical formula for water? H2O, meaning water is made from two hydrogens and one oxygen. Well hydrogen peroxide is almost the same except its got an extra oxygen, so its formula is H2O2. But whilst water is very stable (remember how we needed to put electricity through water to break it down in the hydrogen and oxygen), hydrogen peroxide is unstable, it slowly decomposes to water and oxygen. However when the yeast is added to the hydrogen peroxide that extra oxygen gets released really quickly and you end up with loads of oxygen gas (the washing up liquid is just there so that the gas gets trapped in all that foam).
So why does adding yeast result in the oxygen being released so quickly? Well yeast contains an protein called catalase. It looks like this.
Catalase is a type of protein called an enzyme. Enzymes1 speed up specific chemical reactions. In this case the reaction is:
2 H2O2 → 2 H2O + O2
Which is just a way of saying that 2 hydrogen peroxide molecules turn into two water molecules plus 1 oxygen molecule. The really astonishing thing about catalase is how fast it works. One catalase molecule can break down 40 million molecules of hyrodgen peroxide every second!
1 The word enzyme comes from the greek ενζυμον, meaning"in yeast". Plus things that speed up chemical reactions are called catalysts, hence the name catalase. So if you follow the etymology of these things you end up going around in circles.
Something a bit different for this post. No instructions on fun science experiments I'm afraid. Instead I want to recommend a book that everyone who loves science should read. It's called "The Geek Manifesto: Why Science Matters" (by Mark Henderson)and its a bit of a call to arms for scientist and science lovers everywhere. Amongst other things it describes how poorly scientists are represented in politics. In the UK just one (out of 650) of our Members of Parliament had a career in science before entering politics (and its not better in the USA). Consequently politicians fail to understand how science is conducted leading, amongst other things, to a systematic abuse of evidence to support their policies.
But this evidence abuse and misunderstanding of the scientific method is not all their fault. Scientists too often fail to engage with politicians (and the media). So Mark calls for scientist to do just that, help support politicians, talk to them and make science (and evidence based policies) a vote winning issue.
One of the book's fans, Dave Watts, took Mark's message to heart. He thought that our politicians should read the book so he rallyed the troops and via an online pledge site got scientists to agree to send a copy of "The Geek Manifesto" to every MP in the UK parliament. With the help of the publishers (Transworld, who agreed to match the individual pledges) the target has been reached and books are winging their way to MPs right now.
I joined in the fun and have sent a copy to my MP with the following accompanying letter.
Dear Graham,
Within the next few days you should receive a copy of “The Geek Manifesto: Why Science Matters” by Mark Henderson(Head of Communications at the Wellcome Trust) I hope you enjoy reading it.
A few years ago we engaged on the Royal Society’s Scientist/MP pairing scheme. I found it a most useful insight into the workings of government and the role that science can play in the decision making process.
Unfortunately and despite excellent schemes, like those run by the RS, it seems to me, and many others, that science is greatly undervalued and misused in British politics. Many of our decision makers are unfamiliar with the scientific methods and how it can be applied to policies.
This lamentable state is in no small part due to scientists’ failure to engage with politicians. But this is changing. In recent years scientists have started to form lobby and pressure groups to better make their cases heard.
Mark Henderson’s book follows in this vein. It is acting as a call to arms, rallying scientists and persuading them to make science and evidenced based decision an electoral issue. Therefore many of us consider “The Geek Manifesto” to be an extremely timely and important book. It contains arguments that all rational thinkers should consider. With this in mind hundreds of scientist around the country have pledged to buy and send their MP a copy of the book. Within the next few weeks every MP should receive a copy.
I hope you and your colleagues find the book to be an interesting read.
An offer to help I know from my experience on the scientist/MP pairing scheme that you are a extremely busy working to help you constituents. In turn I believe that scientists must do more to help their MPs understand science and the scientific method. I would therefore like to offer my services in helping to form evidence based views and decisions. My specialist expertise lies in chemistry and biochemistry. However my scientific skills are highly transferable, after all science is more about asking rational questions, solving problems and understanding date than it is learning facts and figures.
Meet the Geeks
Lastly, I would like to draw your attention to your local “Café Scientifique” (details attached); a monthly meeting were local scientists talk, in an informal, setting to members of the public. You are welcome to come to our meetings, which would be an excellent opportunity for you to meet some of your ‘geek’ constituents.
I look forward to your reply, which I will post on my blogwww.t2ah.com .
Sincerely,
Dr Mark Lorch
I'll keep you posted on any reply. In the mean time you can read more about the book and the pledge on blogs here and here and many others. And of course I heartily recommend reading the book.
Solargraphy is a way of tracking the suns movement across the sky usually using pinhole cameras. Its really easy to set up but the best images take months to collect, so you need some patients for this one. Its also best to start them when the sun is highest or lowest in the sky. And since we are only a couple of weeks away from the summer equinox (or winter equinox in the southern hemisphere) now is an ideal time to get your solargraphic cameras ready so they can be deployed on 21st June.
You can collect some absolutely stunning images so its well worth having a go. For example here's six months from my bedroom window. And for more solargraphs take a look at Deigo's awesome collection at solarigrafia.com.
a scanner ( or at a push a digital camera will do)
What to do
1. Cut a small square out of the side of the canister.
2. Cut a square of tin out of your drink can. The square of tin needs to be significantly larger than the hole in the film canister.
3. Take the pin and gently push down on the tin square. DON'T push it all the way through, you just want to make a dimple on the opposite side of the tin.
4. Turn the tin square over and sand down the dimple.
5. Turn the tin over and gently push the pin in again, turn it back and sand down the fresh dimple. Repeat this 2 or 3 times until you have a very small hole in the tin.
6. Tape the square of tin over the hole in the canister (using the electricians tape). Make sure the pinhole is near the middle of the hole in the canister.
EDIT: @solarigrafia pointed out that it hot countries you need more tape than I used here otherwise you end up with it melting and the pinhole falling off. So you might want to wrap the tape right around the canister.
7. Do the next bit in subdued light (I didn't because then I couldn't show you the photos). Cut a section of photographic paper that's about the circumference of the canister in length by a little under the canister's height. The paper needs to fit neatly inside the canister. Stick the paper to the canister (with the double sided tape), otherwise it rolls up over the course of the exposure.
TOP TIP: Double and triple check that the paper is the right way round in the canister. The light sensitive side needs to be facing and opposite the pinhole. I've got that bit wrong before and there is nothing more annoying that coming back to the canister 6 months down the line and discovering you've made that school boy error.
8. Put the cap back on the canister and and if you want belts and braces tape it up.
9. Leave the canister facing out of a window, preferably south facing if you are in the northern hemisphere or north facing if you are in the southern hemisphere.
Top tip 2: Try putting your new pinhole camera somewhere overlooking a building site.
10. Wait for 6 months.
11. Take down the canister, open it up and scan the image. It will be a negative so you'll have to invert the image with some processing software. Anyway, I'll talk you through all that in six months time.
What's going on?
Remember the camera obscura? Well the same thing is going on here. Except this time we have some photographic paper to record the image. The pinhole lets in a tiny amount of light and the paper is actually quite insensitive to light (unless you use developing chemicals, which we aren't) so most of the paper needs a really long time to register any image. But where the light hits the paper directly from the sun the paper is exposed much more quickly so the sun tracks are recorded really well.
I saw this astonishingly simple motor described over at the fab proton's for breakfast blog and had to have a go.
All you need is:
A small stack of 12mm diameter disk magnets (I get mine from emagnets)
A 1.5V AA battery
A length of stiff but bendable copper wire
A penny
Safety:
The magnets are very strong. Watch out they can fly together and shatter.
What to do:
1. Stick the magnets onto the negative end of the battery.
2. Place the penny on the top of the battery.
3. Bend the wire so that it balances on the top of the penny whilst the other end only just touches magnets.
4. And watch it spin!
What's going?
When the copper wire touches the magnet a circuit is completed and electricity runs through the wire. When electricity passes through a wire it generates a magnetic field. This then interacts with the magnets at the bottom of the battery (in the same way as opposite poles of a magnet repel each other) and the who thing spins. Hey presto the world's simplest motor.
We all know about the 3 states of matter, right? There's gases, liquids and solids. Well there's actually more than that (they don't bother teaching you about them in school) and one of them is plasma. It can be made by super heating gases to the point where the electrons get stripped off leaving charged ions and free electrons. Generally you need a lot of heat, like in a star or lightning to make it. Or some clever technology, like a plasma lamps. But it turns out you can also make plasma with a grape and a microwave oven. Safety:
The grapes get VERY hot so be careful when you take them out of the microwave.
The process also produces ozone gas, which is poisonous and can cause breathing difficulties. It doesn't produce a lot of it, but you probably don't want to do this experiment to many times. And if you are asthmatic its probably best to just watch it on youtube.
There is the potential to damage your microwave. I've never hurt mine but just be warned making 3000oC plasma may not do it much good. So ask whoever owns the oven if its OK first.
What you'll need:
A microwave oven
A grape
A knife
Kitchen towel
What to do:
1. Cut the grape in half along its equator. Make sure you keep the two halves attached by a bit of skin.
2. Place the cut surfaces on the kitchen towel to gentle dry them.
3. Turn the grapes back over and stick them in the microwave.
4. Turn it on.
For the sake of this video I've used 4 grapes in one go. I advice you to do it one at a time.
5. When you (carefully) take the grape out you should see that its really pretty singed around the side. Which just goes to show how hot it go.
What's going on?
I have to confess that I'm not sure about this one. And judging from discussions elsewhere on the web there's no clear answer. So if someone would like to chip in and give us an explanation I'd be glad to hear it.
There's all sort of potions and polishes that you can buy to clean up the silver. Don't buy any of them. Because you can find everything you need to get the best cutlery sparking again in your kitchen cupboards.
What you'll need:
Bicarbonate of soda
Aluminium foil
A cup or glass
Some tarnished silver spoon (its best if its solid silver, it will work with silver plated stuff, but you run the risk of removing the plating)
What to do:
1. Put a heaped teaspoon of bicarb into the glass.
2. Tear up 10 to 20 bits of foil and add them to the glass.
3. Put the spoon in the cup
4. Pour on hot water. Water from the hot tap will do fine.
5.Stir and leave for 5 minutes.
6.Take the spoon out and inspect it. All the tarnish will have disappeared.
Before
After
What's going on:
There's some pretty niffy chemistry going on here. First lets dispel a little myth, the tarnish is not due to a reaction with silver and oxygen like a lot of people claim. Iron reacts with oxygen to make rust, but silver tarnish is something different. Silver tarnishes when it reacts with sulfur containing chemicals (usually hydrogen sulfide, which smells like rotten eggs) to produce silver sulfide. Eggs are particularly high in sulfur which is why they make your silver tarnish so quickly.
That's the easy bit. How the aluminium and bicarb work to clean the silver is a little more complicated.
Lets take a look at the chemicals that we start off with. You've got silver sulfide (the tarnish), sodium bicarbonate (the bicarbonate of soda), aluminium hydroxide (the foil is actually covering in a layer of this, the aluminium itself is underneath and we need to get at it).
Step 1: The bicarbonate reacts with the aluminium hydroxide and turns is back to aluminium.
Step 2: The aluminium reacts with the silver sulfide to make silver and aluminium sulfide.
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