Agar makes an excellent media for growing bacteria. In this experiment, students touch nutrient agar Petri dishes with dirty hands, with hands washed just with water and with hands washed with both soap and water. The dishes are then stored in a warm location (98.6 degrees Fahrenheit is ideal) and examined after several days. This experiment teaches children what bacteria are and why it is so important to maintain good hygiene.
At a point in our evolutionary past, life progressed from single-celled organisms to multicellular creatures. Diffusion and surface area-to-volume ratio explain why this occurred. In this experiment, students submerge different sized blocks of phenolphthalein agar in a 0.1% hydrochloric acid solution. As the solution diffuses into the agar, it changes the color of the block. The larger the block, the longer it takes for the solution to get to its center. Cells essentially work the same way. Very large cells are impractical for obtaining nutrients through diffusion, while small cells are more efficient.
In this experiment, ants are introduced to an enclosed block of colored, sweetened agar. Over the next several days and weeks, the ants carve tunnels into the agar (which is also their food). Since the entire structure is largely transparent, students can study the ants as they dig. This allows them to identify the various castes, see the different roles of each and observe the complex network of tunnels that they create.
In this experiment, students study the concept of dissolution and the basic states of matter. There are several containers of water, two each of saturated salt solution, half-saturated salt solution, saturated sugar solution and half-saturated sugar solution. There are also three containers of pure water. One of each set of containers is cooled, so that students can observe the differences in freezing points and one of each is heated, so that differences in boiling become apparent. In the last water container, the water is boiled and agar is added. Once cooled, this turns to a solid, but it will melt again when heated. Sugar and salt raise the boiling point of water but agar effectively (though not literally) raises the freezing point.