Introduce your secondary students to the chemistry subtopic that you intend to explore through a science project. Make your project more interesting to your middle and high schoolers by using phenomena and substances that are well known to your young scientists. If you were studying acids, alkalis and the pH scale, for example, you could introduce the basic chemistry of lemonade and even go as far as to make your own homemade lemonade before sharing it with your students. Following this example, you could also enlarge a copy of the pH scale and pin it up in a prominent place in the classroom before indicating where lemonade would rate on the pH scale.
Inform your students that you will test five different substances, such as lemon juice, vinegar, distilled water, milk and bleach, to see if they are acidic or alkaline. Call out the name of each substance one by one, and get your secondary students to write a hypothesis for every substance involved in the project, indicating what pH they think the substance will rate on the pH scale.
Test each of your products individually to see where they register on the pH scale. You can either use a store-bought pH testing kit and compare the color of the testing strips to the color chart provided, or use a pH meter for a more accurate reading. Either way, demonstrate to your students that acids show up red or indicate a low pH reading on a meter while alkalis are commonly purple or a similar color and register a high pH reading. As you test each substance, write its name on a large arrow and pin it to the pH chart you already have on a notice board to show exactly where it registers. As you are teaching secondary grades, you should indicate that the difference between pH 8 and 9 is not the same as the difference between pH 9 and 10, for example, and introduce the concept of logarithmic scales to your class.
Get students to think about the substances you have tested and whether the substances have any similarities. For example, challenge your students to recognize the neutral, almost flavorless taste of water and understand why this is pH 7 and neutral. Other students should also correlate the flavor of acidic substances such as vinegar and lemon juice, for example. Work to get your class to relate the project findings back to their everyday life as this will help make your project more memorable and the lessons learned will stay with the young scientists.