The combination of powders can be different in each of your categories. The spoiling of food is a chemical reaction. The chemical properties of some substances, like salt and vinegar, can slow chemical reactions and keep foods from spoiling. For example, the vinegar used to make pickles helps preserve those cucumbers. The salt in beef jerky keeps the meat from spoiling.
Temperature can also affect the rate of some chemical reactions.
The coolness of the refrigerator or freezer slows chemical reactions so that foods keep longer before they spoil. Ask someone to give you several powders without telling you what each is. Give each mystery powder a number so that you can sort out the data for each one. Do each of the above tests on the mystery powders. Using what you know about how different powders react to each test, describe the properties of each powder and make an educated guess on the identity of each mystery powder.