Acids and Bases

• Though many think of the standard spewing volcano as an experiment in acids and bases, there are a variety of experiments that are more difficult and intricate that explore the relationship between the two. Acids and bases can be viewed from different angles and are interdisciplinary, allowing you a variety of options. Acidity can be tested in chemistry, medicine, botany and even genetics. For genetics, amino acid sequences in different animals can be compared to see how closely they are related, and in microbiology, test the effects of acid rainfall on the cellular structure of algae or moss.
  
  

Static Electricity

• Static electricity experiments do not only have to consist of hair standing on end or sticking balloons to clothing but can be much more extensive. Build your own electroscope and classify how conductive materials are, design and build a Van de Graaf generator (an electrostatic machine using a moving belt) or build a cloud charge monitor and show how electric the clouds are in your area.
  
  

Microbiology

• Microbiology is a difficult subject and can be used as a hard science fair topic. Growing microbes and studying them has to be calculated and can be difficult. Test the different growing capacities of pH waters, create bacteria from gym shoes or show how much bacteria grows on different surfaces in a home, from kitchen to bathroom.
  
  

Biochemistry

• Generally taught at a high school level, biochemistry-based projects are difficult to do, but not impossible. From enzymes to plant hormones, the subject offers an array of science fair experiments. Determine the properties of enzymes and how they react to different factors, such as temperatures, pH levels and inhibitors. Test the plant hormone Rootone on plant growth and the greenhouse effect associated with it.