Students can use cat food to test for different nutrients, such as starch. Students can use wet or dry cat food as well as a variety of other types of food, such as fruit, bread or chocolate bars, for the sake of comparison. To test for starch, use brown iodine administered in a dropper. Starchy foods change color to a dark, purplish blue or black color. Students should note the changes, if any are observed, in the cat food and other foods.
Students can compare the fat content of various canned cat foods and other foods. For this experiment, students should collect non-fat as well as regular cat food and even canned tuna. They also should collect other foods, such as bread and fruits. Students can rub a sample of each food on small pieces of paper that are cut from brown paper bags. They can compare the fat content of the foods, noting the different greasiness levels by holding the paper bag pieces up to light.
Students can learn how to conduct a formal study with an experiment that requires feeding cats two different cat foods. They can compare grain-free versus standard, dry versus wet or non-fat versus regular cat foods. With the permission of their parents, students with cats as pets can randomly be given a cat food to feed their pets over the course of a month. They will keep track of weight, activity level, quality of fur coat and other health indicators on a weekly basis and bring in their data at the end of the month for the class to analyze.
Students can practice testing substances for pH by determining the pH of different cat foods. Some cat foods have a low or neutral pH to help cats with particular health problems, such as urinary tract issues. Collect various cat foods, low-pH and regular, puree each one separately without adding anything including water, and have students test them for pH with special indicator test strips.