Someday you may find yourself pressed for a science fair project that you, or your child, has put off until the last minute. This can be quite a stressful situation, particularly if you are also out of milk. Should you be lucky enough to find a few cups of unspoiled milk still in the refrigerator you could try any or all of these sour milk science fair projects. Using a digital camera to keep track of each milk storage group and the rate of spoilage can also provide great images for science fair project boards.
The first hypothesis is that milk will spoil at different rates depending on the storage location. Some locations, such as the refrigerator, will require several days or even a couple of weeks to spoil. Although milk will spoil in a matter of hours if it is left in a well-lit window, you may also want to try leaving some open in the refrigerator, inside cabinets and in different rooms of your home. Each cup of milk should be logged and labeled to track its progress. Some cups should be checked every few hours, like the one on the window sill. Others will only need to be checked daily.
Another interesting twist on the spoiled milk hypothesis is to test different types of milk. Most grocery stores carry whole milk, 2 percent and skim milk, but you may also find buttermilk, heavy cream and other types of milk. This experiment could be done by placing samples of each type of milk in one location and charting their progress. Alternatively, for a much more detailed experiment, prepare several samples of each type of milk and several storage locations. More types of milk and more storage locations will create a lot of data for testing your hypothesis. Perhaps one type of milk sours faster in direct sunlight but more slowly when left open in the refrigerator.
Testing temperature hypotheses can be done in at least two ways. You can test the storage temperature or the starting temperature. Changing the starting temperature can be done by dividing the milk into three groups. One group is then boiled, the next refrigerated and the third is frozen. Once all three groups have reached their starting temperature, place them into storage and track their progress. You can also track their storage temperature by placing a thermometer into each storage container. When you record your observations, you will also keep track of the temperature displayed on the thermometer.
The last, and in many cases the fastest, method for spoiling milk is to add a chemical agent to the storage container. Acid is known to spoil milk, but this hypothesis test the time required to spoil milk in different storage locations after being exposed to an acid. For greater verity, you can also use acids of differing strengths. The most common acid used in this experiment is lemon juice, but you can also try oranges, limes, pineapples and other acidic fruits. After creating and storing your acid/milk mixtures, you will need to chart their progress. This is another example of a sour milk experiment that will typically only take a few hours.
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