Australia's Science Forum

Dear Barbara,

I have a demonstration where foam rises out of a measuring cylinder at a fast pace and lands in a pnuematic trough.
Is that of any use?
Maree

One of our teachers does that "trick". He just uses a squirt or two of morning fresh(apparently the best for bubbles). He uses a glass pasteur pipette on the end of a rubber tube attached to the gas tap to bubble the gas through the water and lights the bubble with a taper. He also uses the bubble mixture,you buy from woolies in small bottles, used for parties and weddings.
Hope that helps

We generate Hydrogen in a conical flask (Zn in HCl) and use a fairly narrow piece of tubing to bubble the H2 into a large measuring cylinder with water and a big squirt of dishwashing detergent. Then you can light the bubbles as they rise to the surface. With practise, you can get a perpetual "pockety-pockety" of little flames happening, rather than one big BANG!

Kristin

All sound great to me. Thanks...will try. Whats the bubbles in a measuring cylinder prac?I'm not a lover of big bang chemistry! but we will give these a go.

Well Barbara, here is the Foam Column:
FOAM COLUMN

Materials: 500ml measuring cylinder, glass pneumatic trough, spatula
Chemicals: 50ml 100vol H2O2 , MnO2 , detergent
Procedure: Place two large spoonfuls of MnO2 powder in the bottom of the measuring cylinder. Add a generous squirt of detergent to cover the manganese dioxide. Now stand the measuring cylinder in the centre of the trough. Have paper underneath the trough.
Now pour the hydrogen peroxide into the cylinder. There is a change of temperature.
Theory: H2O2 decomposes slowly in the absence of a catalyst, forming water and oxygen. Addition of a catalyst such as MnO2 lowers the activation energy for the reaction, causing rapid production of oxygen gas. The detergent causes this gas to produce a column of foam.

Safety: 100 vol H2O2 can cause severe burns to skin and eyes. MnO2 must not be added to H2O2 of this concentration in the absence of detergent as the reaction becomes violent and the heat released causes boiling to occur.

Wear Safety Goggles and Gloves.

The students here love seeing this demonstration.
Good Luck

Maree

You can google "Elephant's toothpaste" to get other recipes for this one. We use it to demonstrate rates of reaction. Get 100ml of 30% H2O2 and warm it in a microwave (presuming you store your peroxide in the fridge, it will be cold, so try 2 mins in microwave), and pour into a large measuring cylinder -250mL or 500mL. Get another 100ml of COLD H2O2 and pour it into a second measuring cylinder. Add a generous squeeze of dishwashing detergent to each. Stand both cylinders in a trough. Have a teacher at your side, and measure out one spatula full each (ie 2 spatulae) of KI (Potassium Iodide). Say "One two three!" or something similar and add the KI to the cylinders. STAND BACK.
The hot H2O2 will react violently, with a column of bubbles shooting up into the air. The cold H2O2 will react slowly, but eventually produce more bubbles, as the O2 is released more slowly, and therefore has time to form bubbles in the soap mix. DON'T TOUCH the foam, and DON'T let the kids touch it. The iodine generated can invade your fingernails and hurt for days, speaking entirely from personal experience. However, you can observe the heat generated by the reaction, in the form of steam emanating from the bubbles, from both the hot and the cold H2O2. The KI is a cleaner catalyst then MnO2, but beware of the iodine.

Good Luck. Kristin

WE do this experiment quiet often - put some bubble mixture in a butter container attach a Thistle funnel to some rubber tubing and attach to gas outlet.
Put thistle funnel in bubble mixture - take out - turn on gas - then with a taper candle on a meter long ruler we then ignite the bubble. the kids love it. You get a big gas fire towards the ceiling - lots of ohs and ars from the kids -