Time: 55 minutes (including the reading of the directions). Now set your clock for 55 minutes.
???In science, a theory is a reasonable explanation of observed evnets that are related.
A theory often involves an imaginary model that helps scientists picture the way an
obseved event could could be produced. A good example of this is found in the kinetic
molecular theory, in which gases are pictured as being made up of many small particles
that are in constant motion.
???A useful theoty, in addition to explaining past observations, helps to predict events
that have not as yet been ovserved. After a theory has been publized, scientists design
experiments to test the theory. If observations confirm the scientists predictions, the
theory is supported. If observations do not confirm the predictions, the scientists must
search further. There may be a fault in the experiment, or the theory may have to be
revised or rejected.
???Science involves imagination and creative thinking as well as collecting information
and performing experiments. Facts by thenselves are not science. As the mathematician
Jules Henri Poincare said: "Science is built with facts just as a house is built with
bricks, But a collection of facts cannot be called science any more than a pile of bricks
can be called a house."
???Most scientists start an investigation by finding out what other scientists have
learned avout a particular problem. After kmown facts have been gathered, the scientist
comes to the part of the investigation that requires considerable imagination. Possible
solutions to the problem are formulated. these possible solutions are called hypotheses.
???In a way, any hypothesis is a leap into the unknown. It extents the scientist s
thinking beyond the known facts. The scientist plans experiments, perform