Make some soap and devise tests to see how the soap compares to commercially produced soaps. Use caution when using the soap on the skin. The soap may be caustic if not all the lye has been neutralized. Try canola oil or olive oil instead of lard. All members of the group of chemicals called alcohols have an -OH group on a carbon chain.
Most fertilizers contain nitrogen, potassium and phosphorus.
For each mineral nutrient which a plant needs, identify one natural compound or source in the soil for this nutrient. Some fertilizers for houseplants are advertised as 'slow-release' fertilizers. Food additives can be used for more than preserving food. Go to a grocery store and make a list of the ingredients in each brand of ice cream that is sold there. For each brand, make a poster listing each ingredient, its chemical formula or the class of compounds to which it belongs and the reason the substance is used.