Instead of golden syrup you could use treacle or corn syrup: something gloopy and messy. For alcohol you can use almost anything from spirits to rubbing alcohol. If you’re a kid, please ask whoever is in charge before raiding the drinks cabinet (this is generally a good rule in life).

You will be putting all of these into one glass, so find a tall one that is reasonably straight-sided. The more angled the edges of the glass are, the more of each liquid you will need as you go along - this could get tricky. You’ll need about one sixth of a glass worth of each liquid, as shown above.

Start with the glass containing the syrup and carefully pour the dishwashing liquid into it. You want to pour down the sides of the glass if possible, this will help stop the two liquids mixing. For these two it should be easy enough as they are both fairly thick. Let the glass stand for a moment and you should see that the two liquids make layers in the glass.

Now we add the rest of the liquids, in the order shown in the image at the top. Pouring down the side of the glass may not be enough to prevent these remaining liquids from mixing. It helped me to use a teaspoon. Hold the teaspoon inside the glass just above the surface and pour gently into the spoon, allowing the liquid to pour over the sides. In this way, the liquid you are pouring is placed on top of the existing ones much more gently. Be careful and pour slowly and you should be fine. You can always practice your pouring in another glass if you want to.

Hopefully you will end up with a nice, layered glass of different coloured liquids. Why? Well it is all to do with density - the mass per volume - of the liquids. Liquids at the bottom have higher densities than those at the top. All liquids have different densities as well many other properties. We can explore some of them using our layered glass.

Take a chopstick, or similar stick-like object and insert it into the glass. Don’t disturb the glass too much though. See how the chopstick looks now. Each liquid bends the light coming through the glass in a different way. This is related to the density but is actually a property of all materials called the refractive index. In general the refractive index increases with density. It is a measure of how much light is bent as it passes through a material.

We can also explore two more properties of liquids: viscosity and miscibility. Take hold of the chopstick and stir the glass up. Stir well, but try not to spill the contents. Watch and feel how the liquids mix.

You’ll notice that it is very hard to mix the syrup and that you can also feel the washing up liquid dragging against your stirring. This is because heavy liquids tend to be viscous. Viscosity is the measure of a liquid’s resistance to you changing its shape. The syrup is highly viscous, i.e. it resists your chopstick very strongly. The water, alcohol and oil offer almost no noticeable resistance at all, by comparison. This is because they are all similarly viscous and we are all used to how water ‘feels’.

After you stop stirring the glass, wait a few moments for it to settle down again. Watch it during this time and you will see it appear to organise itself. Miscibility is the measure of how well two substances mix. Water and alcohol are miscible because they mix together just fine. You can see that they do not separate out again after you stop stirring.

Water and oil are immiscible. This means that they do not mix. It doesn’t take long after you stop stirring for the oil to float back to the top. Would you say that the washing up liquid is miscible with any of the others? I found it hard to tell because both it and the syrup were so viscous I could not stir them up very easily!

Liquids, and their many properties, shape all sorts of things in the world around you. Refraction, density, viscosity and miscibility are important in our everyday lives.

Anyone who has had to clean oil-based paints off a brush with water knows something about miscibility. If you have tried to hook something out of a pond or swimming pool who have experience the frustration of refraction. You also know that you float in the sea, this is because of the difference in density between the salt water in the sea and the water in your body. Have you ever had to wait for ketchup to slowly pour out of a bottle because of its high viscosity?

In astronomy you can see some of these properties in action. The planet Jupiter has a series of coloured bands running across its surface. The different fluids that make up Jupiter’s enormous mass do not mix well because of their make-up. The hydrogen- and helium-based fluids are thought not to be miscible and this is part of the reason that we see the striking bands or colour on the planet’s surface.

Refraction and density are a big problem when observing through a telescope. The air becomes unevenly heated and this creates patches of the sky with higher refractive indices than others. Pollution also changes the refractive index of the air. The result is a fuzziness that astronomers call the ’seeing’. Because of this, astronomers prefer to put telescopes high-up and away from cities with their hot buildings and smog.

Viscosity is important in simulations of planet formation. Disks around young stars are made up of different materials and if they get dense enough they will become highly viscous and drag against the force of gravity as it tries to force them around the central star. The result is that parts of the disk could be dragged inward and this could greatly determine the formation and evolution of planets.

Spectrometers are used, like prisms, to spread light out into the component colours. This enables us to understand the compositions of everything from stars to streetlights. Here I show you how to make your own spectrometer and give you a few examples of what you can see with it.

What You Need:

• A cardboard tube (toilet roll or kitchen roll tubes are just perfect, in the pictures here, I have used more black card to make a tube myself.)
• 2 square pieces of black card (approx 8cm x 8cm)
• Black tape or masking tape (something that blocks out light)
• Razor blades (nothing fancy just cheap blades that are not attached to anything)
• A stanley knife
• An old CD

Make a Diffraction Grating:

Cut a small square hole (approx 1cm across) in the middle of one of your 8cm x 8cm black cards. Break the CD into pieces, just snap it. You’ll need a section of the broken CD that can nicely cover the 1cm hole in your card.

Using a bit of sticky tape, peel away any cover remaining on the piece of CD, so that it is transparent. Use tape to stick it over the hole, creating a sort of window. This will be our diffraction grating.

Make a Very Fine Slit:

Using a stanley knife, cut a slit in the middle of the other piece of 8cm x 8cm black card. This slit should be about 2cm long and just a few millimetres wide. Tape the the two razor blades either side of the slit. They should make an even narrower slit, just 1mm or less if possible!

The aim is create a very fine, narrow slit though which light can travel. Make sure the blades are securely attached with tape for safety.

Make the Spectrometer:

This is the easy bit! You now attach the two square cards to either end of the tube using the dark tape. You have to attach it in such a way that no light is let into the tube accidentally (hence the dark tape). When you look through the diffraction grating, you only want to see light coming from the slit.

Testing Out Your Spectrometer:

The best way to see how this works is to use daylight. Just point the spectrometer toward a window during the day or up at a cloud if you’re outside. You should not ever look directly at the Sun. You should see a nice, smooth spectrum (rainbow) somewhere in your field of view in the tube. Here is a photo of a cloud taken through my own spectrometer. The bright white light is the slit and spectrum is just off to one side.

What’s Happening?

When light enters the tube though the slit it spreads out - all waves do this when passing through small slits. The CD then makes the separate colours visisble to your eye. You see a nice, even spectrum from daylight sources because daylight is made up of all the colours of visible light from the Sun. Once you can see this pattern, you can start trying to find the spectra of other things.

In our physics lab we have lamps of different chemical make-ups. These let us see pure light from different sources. Here are a few I took today, all photos taken by my own camera through my own, homemade spectrometer.

Here is the spectrum for Zinc, which you can see contains some red and blue but very little green.

Cadmium is very distinctive, with short sections of each of the three primary colours and very little between them. It is less spread out than Zinc. There is a big gap between the green and red sections.

Krypton is seen to be fainter than the others here, but the spectrum is still visible. The blue section has become much more violet or indigo here and the green is greener than it was in Cadmium.

The Astronomy Connection:

This is how astronomers know what stars are made of. They use advanced spectrometers to measure the spectrum of stars and pull out the ‘fingerprint’ patterns of colour that you see above. Each element has a unique set of spectral lines (colours) and these can identify the presence of different chemicals in stars, nebulae and just about everything else.

This is the whole spectrum of the Sun. It is so detailed that it had to spread onto multiple lines to see it properly! You’ll see that in fact it is not perfectly evenly spread out as I suggested earlier. This was taken with a very advanced spectrometer that has a greatly increased sensitivity compared to one made here, but its based on the same principles.

Things to Look At With Your Spectrometer:

• Sodium streelights
• Compare daylight to a lightbulb.
• Different light bulbs look different (that’s why energy saving bulbs light up the room in a different way).
• Neon signs.
• TV  and computer screens.
• LEDs from computers or remote controls (these give very pure spectra, often only one colour).

Have fun with your spectrometer and why not try and take a photo through it? It worked fairly well for me. I’d love to see any photos you take with it, or of it. Let me know how you get on. Thanks to the Science Made Simple team for this great idea!

What you will need:

• A regular drinks can
• A pot of cold water big enough to submerge the can
• A pair of tongs
• A kitchen hob (gas or electric is fine).

What to do:

Now you have to be careful with this one. The tongs have to be good or you’ll burn yourself. If you’re a child reading this, then make sure someone supervises you while doing this experiment. Reading though all the instructions before you start out is vital. I recommend having a couple of attempts, so maybe have two or three cans ready. So let’s begin:

Whilst you are filling up the pot of water why not drink the coke or whatever is in your drinks can. We don’t need any of the contents for this experiment, just an empty can. Once it is empty, rinse it out and place about two tablespoons of water in the can.

Now take your tongs and get a firm hold on the can. Hold it over the kitchen hob. We need to boil the small amount of water we have put in the can. This won’t take long and you’ll know when it’s worked because you’ll see steam coming out of the hole at the top of the can. Let it steam for a minute or two to be sure the water has all boiled.

Now here’s the cool bit. Keeping the can in between the tongs, take the can directly from the hob and dunk it, upside down, into the pot of water. The can will instantly and violently be crushed! It will happen very quickly so be ready. When I did it, it made a loud smacking sound as it went under water. I did it twice because I missed it the first time!

What is happening?

There is some great physics going on in this simple experiment. When you heat up the can and boil the water inside, the can fills with steam and pushes out all the air. Then when you dunk the can into cold water, the steam quickly condenses into water and there is no air pressure inside the can to support it. The can cannot resist the forces pushing on all sides from the water and air above it. Therefore it is crushed instantly!

Balloons:

Air pressure is also at work in balloons. When you blow air into a balloon you are artificially increasing the air pressure inside it and the rubber skin expands outward, forced by the force of the air molecules bounding around inside it.

You can ‘crush’ balloons by dipping them into liquid nitrogen. This condenses the air inside into a liquid and the balloon goes flat as a pancake. Here can see a video of a balloon that has been dunked into liquid nitrogen thawing out. The air boils back into a liquid and the balloon re-inflates. We filmed this last year in our first year undergrad physics lab.

Enjoy playing with air pressure and feel free to send me any images of your crushed cans!

Microwaves, fall on the electromagnetic spectrum, between radio waves and infrared waves. They are usually around the size of a few centimetres and you may well be very familiar with them as they are produced by the microwave oven that might just be sitting in your kitchen.

Microwave ovens use a particular microwave frequency to excite molecules of water. Since water is present in lots of food and drink, this means that microwaves heat up lots of useful stuff - and they do it quickly. The fact that microwaves are now readily available to most of us in the western world and they are only a few centimetres in length, means that you can measure the speed of light in your very own home.

What You Need:

The quickest and tastiest way to perform this little experiment is with marshmallows, but chocolate chips also work. You’ll obviously need a microwave oven as well, and a large, microwaveable dish. You will need a ruler, too.

What to Do:

Get your large, microwaveable dish and place a layer of marshmallows at the bottom of it.Remove the turntable from the bottom of the microwave oven. If you don’t, then this experiment will not work at all. If your microwave doesn’t have a turntable, it means that the turning mechanism is elsewhere and you’ll need to find a regular microwave oven to try this experiment.

Cook the marshmallows on a low heat for a couple of minutes, or until you see parts of the marshmallows starting to bubble. When you do, remove the dish and take a look at the marshmallows.

You ought to see that they have not melted evenly. In fact you should be able to see a regular pattern has formed, drawn out in melted-mallow. It depends on your microwave oven, but you should see a melted/unmelted pattern across the dish in some direction. When I tried it at home, my oven created long melted strips next to long unmelted strips (see above).

This regularity is caused by the same mechanism that heats up the food you place into your microwave oven. The appliance generates microwaves which very quickly form standing waves (see animation above) inside the cavity inside, where you put food. As the food rotates around, it passes through the standing wave nodes and this excites the water molecules, heating the food.

Measure the Microwaves:

Take your ruler and measure the distance between the melted parts of the marshmallows. You should find that there is an even pattern of melting and that the distance between them is something like 5 or 6cm. Why? Because that is the distance between the nodes of the standing waves.

Without the rotating mechanism, the food does not move around and cook evenly, instead it just heats at the nodal points. Using your marshmallows you have created a ‘map’ of the microwaves in your microwave oven!

Find the Frequency:

Finally you need to know the frequency at which your microwave oven operates. It is usually written on the back somewhere in small writing. Most standard microwave ovens operate at 2450 MHz. If you cannot find the value on the back of the oven, you can take it for granted that 2450 MHz is about correct.

Measure the Speed of Light:

Now you have what you need to measure the speed of light. You just need to know a very fundamental equation of physics:

Speed of a Wave (c) = Frequency (f) x Wavelength (L)

The distance between the melted sections of the marshmallow is in fact L/2, because there are two nodes for each wave (see animation). So if you have measured 6cm and your oven operates at 2450 MHz, then your measured speed of light is (0.12 x 2450,000,000) 294,000,000 metres per second.

The agreed value of the speed of light through a vacuum is 299,792,458 metres per second. See how accurately you can measure it? what could you do to make the experiment better, and thus get a closer answer?

Now You Can Eat the Gooey Melted Marshmallows:

…and make yourself sick. Yay!