Tom is a high school science student. He has recently learned that the chemical reaction associated with burning often involves combining other compounds with oxygen. Since natural gas is composed mainly of methane, which is a compound containing one carbon atom and four hydrogen atoms, Tom formulates a hypothesis that the process of burning natural gas produces water vapor. To test this hypothesis, Tom places a cold pot of water on his gas stove and turns on the flame. For a brief period of time, Tom notes a clear liquid condensing on the outside of the pot. The liquid is colorless, odorless, and tasteless, and prevents kitchen matches, which have been soaked in it, from lighting. From these observations, Tom concludes that his hypothesis is valid for this particular experiment.

While in his high school biology class, Tom is still thinking about things that contain water. He reads about living things and the composition of cells in his textbook. To learn more, Tom goes to the library to look at several books about cells. After his research, he sets up an experiment in which he takes a small amount of frog muscle tissue and heats it on a hot plate without burning it. He positions a beaker of cold water over the muscle tissue and notes that small droplets of water are condensing on the underside of the beaker. He tells his teacher about this experiment, and they repeat the experiment in class using a number of different animal and plant parts. Tom’s classmates also note similar condensation in their experiments. From this information, Tom formulates the conclusion that all living things contain water, and he adds to the body of support of currently accepted biological theories of the composition of living things.