If you have never done this you should get a teacher to show you or try it at home. I have written it for an experiment I was showing off to another group of students. It has messed up some of the formatting but I’m sure a teacher could fix it for you.
Red food colouring
600ml coke bottle
1. Half fill bottle with vinegar and add a few drops of red food dye and a squirt of dishwashing liquid
2. Put bottle in tray and mound sand around it to make it look like a volcano
3. Add baking soda
4. Chemical reaction takes place and red foam ‘erupts’ looking like lava
Why does this happen?
Vinegar is made from grapes and is often described as bad wine. The yeast used to make wine convert the sugar in the grape (glucose) into alcohol (ethanol).
Under warm conditions however the yeast begins to die as a common species of bacteria, Acetobacter, thrive. Acetobacter convert ethanol to acetic acid.
This is why you can’t get drunk on vinegar event though it is made from wine.
So our vinegar contains lots of acetic acid. In this experiment we added baking soda and got bubbles. To see why this is we have to know what is in baking soda.
Baking soda is largely sodium bicarbonate. Sodium bicarbonate is an example of a base which will neutralise the acetic acid with some consequences.
When sodium bicarbonate is added to acetic acid you create a very weak and very unstable acid called carbonic acid.
Carbonic acid immediately breaks down to form water and carbon dioxide
As the CO2 forms in the vinegar it forces its way to the surface because it is a gas. As all the gas is trying to do this at once millions of tiny bubbles form. Instead of burst at the surface the bubbles remain intact because the dishwashing liquid traps them. The bubbles fuse together and push each other up and out of the top of the bottle creating our lava.
Something to add on: The balloon inflates because the CO2 is released into it, rather than into lots of tiny red bubbles. The balloon drops faster because it is CO2 as opposed to N2 and O2. Every molecule of gas in the ‘volcano balloon’ has an extra ‘C’ on it and so the gas is heavier than N2 and O2.
You can also make other frothing mixtures, such as by very carefully adding some aqueous potassium iodide solution to a mixture of some detergent and aqueous hydrogen peroxide solution. This mixture makes a froth that is known as ‘elephants toothpaste’! You can find other mixtures by Google-ing something like ‘chemical volcano’. If you decide to try making any of these mixtures then please be very careful and get your teacher to help you.