Hobbies And Interests
Containers
Soft drink bottles work well for this project. Clean these bottles first by washing them with detergent and warm water. Thoroughly rinse the bottles after washing and put them aside to air dry. Remove any stickers or labels, together with any adhesive glue that held the labels in place. It is not necessary to keep the bottle top, as sealing the bottle will not influence the outcome of this science fair project.
Bacteria
Collect a water sample from either a local pond, or from a mature aquarium. Obtain a little water from the aquarium filter as well, to make sure that there are enough bacteria in the water sample. Test for bacteria in the water by drawing up a tiny amount of water in a pipette and looking at this sample under a microscope. Various types of bacteria are visible in the drop of water. Many species of bacteria move slowly, but have hair-like growths on their bodies, which will be moving, typically in a wave-like motion.
Full Sun
Fill the soft drink bottle with the water sample and place the bottle on a window sill or counter that receives full sunshine for two to three hours per day. The sun light will destroy bacteria in the water sample. Ensure that the bottle is standing in full sun light and that sun shines on the bottle for a several hours. Remove a drop of water from the bottle after three hours has passed and place this on a microscope slide.
Confirming Results
The bacteria that are visible on the microscope slide will no longer be moving around. The sun's energy has destroyed all of the living colonies. Solar energy is a clean and cost-free way to destroy bacteria in water and has practical applications for third world countries, where boiling water or using chlorine as a disinfectant is not always practical.