Surfing Scientist Ruben Meerman demonstrated three cool science experiments you can do with the kids at home.

1. Christmas Candle Trick

What to do:

1. Float a tealight candle in a plate of water
2. Light the candle
3. Now cover the candle with a large glass bottle or jar

Explanation:
The flame goes out slowly, then the water gets "sucked" up into the bottle taking the floating candle with it. You might suspect that the oxygen being consumed by the flame is doing the trick but the main reason it works is heat. The candle flame does consume a lot of oxygen but it simultaneously produces a roughly equivalent volume of carbon dioxide gas.

Heat is the main reason it works. Heat air up and it expands, cool it down and it shrinks. If you look closely, you'll see bubbles escaping through the water around the rim of the bottle. That's because the air inside is expanding but so some air "escapes". When the flame goes out, the hot air inside the bottle cools and contracts. This produces a lower pressure inside the bottle than outside. The greater atmospheric pressure outside then forces water up into the bottle until the pressure inside is equal to the outside.


2. Psychedelic Christmas Colours

What to do:

1. Pour some full cream milk into a dinner plate
2. Squeeze some drops of food dye into the milk
3. Add a drop of detergent onto the edge of the plate so it runs down into the milk
4. The colours begin swirling like a psychadelic pattern
5. You can add more detergent if the motion stops

Explanation:
Like milk itself, this classic experiment is actually quite complicated. Milk is a suspension of tiny fat globules (about 4% by volume) in water, plus a whole range of proteins, sugar (lactose) and nutrients like calcium. Detergent is a form of surfactant (short for surface active agent) - individual detergent molecules can bind with both water and oil.

The swirling effect in milk is probably driven by the detergent molecules racing around and coating the fat globules. As the detergent molecules are "consumed" by the fat, they create currents. You'll notice colours from the opposite edge of the plate appearing near the detergent and then shooting across the surface.

A bit more info about detergent:
Detergent molecules "prefer" being at the surface of water or oil because they are long and have two distinct ends - one end "loves" water while the other "hates" the stuff, but "loves" oil. A single detergent molecule in water gets forced to the surface where it points its water hating tail up into the air - rather like a duck with it's head down and bum up.

You can't see it, but add lots of detergent in water and the molecules do truly amazing things. They spread to cover the entire surface. The remaining molecules zip around under the surface and latch onto each other's tails to form tiny droplets with the water loving tails pointing out. These are called micelles, and are effectively "hiding" their tails from the surrounding water.


3. Softdrink Fountain

What to do:

1. Wrap a sheet of paper around a roll of Mentos to make a cylinder and secure with tape
2. Unwrap the Mentos (some other mints work okay - Mentos works best)
3. Place all the Mentos in the paper cylinder
4. Carefully open a 2L bottle of softdrink (Diet Coke works best - many others work well but lemon and orange flavours won't work)
5. Hold a credit or business card over the mouth of the bottle
6. Hold the cylinder directly over the hole
7. Remove the credit card so all the Mentos fall directly into the bottle
8. Stand back!

 

 

See more explosive photos from Sunrise set!

Explanation:
The fountain erupts because softdrinks contain lots of dissolved carbon dioxide gas. But in order to form, a bubble has to overcome the incredibly strong tension between the water molecules that surround them. They simply can't do this on their own. They need a foreign particle or a tiny imperfection like a scratch to form on. These imperfections are called nucleation sites.

Mentos appear fairly smooth, but at the microscopic level, they are covered with millions of nucleation sites. Drop one Mentos into a glass of softdrink and the bubbles go crazy. Drop a whole roll of Mentos into a bottle of softdrink and it's a bubble bonanza. Because Mentos sink fast, the expanding bubbles form at the bottom of the bottle. And because they take up much more room than dissolved carbon dioxide, they force the softdrink up out of the bottle.

Many other softdrinks work well but Diet Coke seems to be the best - probably because it contains the most CO2. Lemon and orange flavoured softdrinks don't really work (too light on the fizz). Other lollies work too, but Mentos seem to be best.

More info about bubble formation:
The tension in a bubble's walls is directly related to its radius (size). The smaller a bubble, the greater the tension in its walls. It's the same for balloons and this is the reason a tiny water bomb balloon is so difficult to blow up compared to a larger party balloon. The scientific explanation is known as Laplace's Law. For bubbles to form out of nowhere, they would have to grow from a radius of zero metres - but this equates to infinite tension in its walls and can't happen. But a tiny scratch or speck of foreign matter allows bubbles to form because now, it's radius doesn't need to start from zero. Wherever you see bubbles forming, there's a tiny scratch or imperfection helping it along. They're called nucleation sites.

More info

uben's book, Surfing Scientist - 40 Cool Science Tricks, is available from ABC Shops and ABC online. 

The Coke+Mentos trick on Yahoo! VIDEO