A baking soda volcano is a classic project for any elementary science fair. Children love to watch the erupting foam, and it is usually exciting for adults as well. Because baking soda is a base substance and vinegar is an acidic substance, when the two mix it causes a reaction -- making the volcano a memorable visual demonstration of basic chemistry.
Stand the soda bottle in the baking pan. Tape the bottle to the pan so that it won't tip over. Set it aside. Mix the flour, salt, oil and water in a large mixing bowl. The mixture should turn into fairly firm dough.
Mold the dough around the soda bottle to form the cone-shaped volcano, making sure that no dough is dropped inside the bottle. Leave the opening at the top of the bottle clear. If the dough doesn't want to stick, let it dry a little before moulding.
Heat the water until it's warm. Add the red food colouring (other colours could be used if desired). Carefully pour the water inside the opening of the bottle. Fill the bottle almost to the top. Use a funnel for this process to minimise spills.
Create the volcano by adding the dishwashing detergent drops to the bottle. Pour the baking soda inside as well -- the funnel helps here as well. This prepares the volcano for eruption. If you are taking the volcano to a science fair, stop at this step until you are ready for your presentation.
Make the volcano erupt by slowly pouring the vinegar into the bottle opening. It should immediately start to foam and ooze over the top of the volcano. This process also gives off carbon dioxide, which is what real volcanoes emit.
When transporting the volcano from one location to another, the bottle cap can be screwed back on the top of the bottle to eliminate spills. The detergent is what causes the volcano to foam. The vinegar and baking soda just create carbon dioxide. Colours can be mixed to make a more realistic-looking volcano foam.
If the proportions are off in making the volcano, it will not erupt properly. Try to have a trial run before the final project is due to ensure the volcano will erupt as planned. If making the volcano for a science fair, consider making the internal solution at the location of the event. This will help eliminate mistakes and spills along the way.