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'Cloud in a Bottle'


You will need:

- empty 2l fizzy drink bottle (very important it held a fizzy drink to be sure it is strong enough)

- about 2 tablespoons of lukewarm water (or room temperature clear spirit like vodka)

- a car-tyre pump with the football-inflating pin attached

- some self adhesive draught excluder or similar foam to make a good sea

1. Wrap the draught excluder tape around the inflating pin so that you create a stopper big enough to fill the neck of the bottle when it is squeeeeezed in.

2. Place the vodka or lukewarm water in the bottle and swish it around for about 20 seconds to make sure that the 'atmosphere' inside the bottle becomes saturated with vapour.

3. Connect the pump to the bottle and pump until the bottle begins to creak A LITTLE. You are not trying to explode the bottle! With my pump this is four to five strokes. It becomes hard to hold the stopper in with much more. You may notice the pump getting warm due to the high pressure.

4. You have now created a high pressure chamber. You will see that the air inside is very clear. This is how the air is at ground level. It is under high pressure and the vapour is invisible.

5. Now remove the stopper.

6. You will hear a huge rush of air and the air pressure drops very rapidly inside the bottle. The bottle should feel a bit cooler. This cooling and lowering of pressure causes the vapour to condense and make droplets. This is what happens as warm moist air rises into the atmosphere. The water droplets reflect the light to make a lovely cloud.

7. Please share your photos on Facebook or Twitter.


If you have seen this, you will know it is VERY MESSY, please wear aprons and consider doing it outside!

You will need:

- A leg from an old pair of tights. The black opaque ones work well as they are less likely to burst and the colour contrast is fantastic.

- Two big breakfast bowls of cold porridge (about 300g oats). Follow the instructions on the packet, using water for the mix. Allow to cool.

- A cup of very strong coffee (at least 4x strength to give you an appropriate colour)

- A handful of raisins or sweetcorn

- A cup of water

- A big mixing bowl

- A big mixing spoon

- Scissors

- A tray or wipe clean work area and lots and lots of wipes

1. Place the porridge, coffee and sweetcorn/raisins into the big mixing bowl. This is your stomach. Stir it around, if it is hard to mix, add a bit of extra water. It needs to be fairly runny to give maximum effect. Your stomach is a muscular elastic bag which churns your food up. This leads to mechanical break-down of the food. There are also special enzymes present which start to break the food down into small enough parts to be absorbed by the body. If you see bubbles escaping, these would form burps in a real digestive system.

2. Once your breakfast is nicely mixed it passes from your stomach into your small intestine. It is called the small intestine because it is narrow. You need to pour your mixture into the tights to replicate this. DO THIS OVER A TRAY IT GETS REALLY MESSY.

3. Hold the open end of the tights closed while you squelch and knead the walls of your small intestine. This is what happens in your body too. The intestines are very muscular and waves of contractions help to move the food along the tube. This movement also helps to mix the contents so the digestive enzymes can keep working.

4. You will notice that the liquid is now oozing out quite nicely. In your intestine the broken down food (like this liquid) is absorbed into your body through lots of tiny fingers in the wall of the intestine. The goodness (and some bad things) from your food passes into your blood stream and is carried away to be processed by your body.

5. Your intestine model now contains the food which you have not yet digested. Lets move it on to the large intestine.

6. Now hold the tights up in the air by the open end. Squeeze the contents down until they are trapped at the toe-end. This is now your large intestine. It is wider than your small intestine. In the large intestine digestion continues and is helped by the bacteria which live there. They eat the food which you cannot digest and often produce gas. They especially like to feast on beans which is why you trump more after eating baked beans.

7. You should now have a tray with gloopy liquid in. This would be absorbed by your body. Squeeze out as much liquid as possible.

8. Your large intestine will now contain the food you were unable to digest. Just like in the body.

9. When your food reaches the end of the large intestine it gets to the bowel. You open the muscles in your bottom to poo. You will have to help your model by cutting the end open with scissors.

10. You will see that the poo contains undigested oats and the sweetcorn/raisins which were unable to pass through the walls of your model. You can test how long your own digestive system takes by eating an adult size portion of sweetcorn and seeing how long it takes to emerge.

11. Please send photos of your model intestines. Let me know if you do the sweetcorn test on your own digestion (but I am less keen on photos of that one!).