One of the classic grade school science projects is the homemade erupting volcano. Often, kids will make the volcano erupt by mixing baking soda with vinegar, or adding mentos candies to diet cola. Another method is to add salt to diet cola. When you do, bubbles quickly form on the edges of the salt crystals and then rise to the surface. This makes the cola foam up and bubble out of its container. Though the reaction is not as violent as with baking soda and vinegar or with cola and mentos, it will still look like an erupting volcano.
Using clay or play dough, build a model volcano inside a box or on a board. If you wish, use different colours of clay or play dough to make the volcano look more realistic. For instance, use brown for rocks and dirt, green for grass and trees and red for lava. Make sure to leave enough space in the centre of the volcano to fit a can of cola. A box with low sides will help contain the cola/salt mixture as it bubbles out, making cleanup easier.
Open the can of diet cola and place it in the centre of the volcano. Though carbonated drinks with sugar in them will also work, the sugar will slow down the reaction as well as leave a stickier mess, making cleanup harder.
Hold the funnel upright, placing a finger over the hole at the bottom. Measure two tablespoons of salt into the top of the funnel.
Still keeping your finger over the bottom of the funnel, place it over the can of diet cola. When you are ready, remove your finger and let the salt drop into the can.
The cola will begin to foam and bubble out and over the sides of your volcano and will continue until nearly all the cola inside the can is gone. Wait until the reaction is finished and then start cleaning up.