Where does the matter come from for plants to grow? Matter cannot normally be created or destroyed, only moved from one place to another.

Disproof is more reliable than proof? Aristotle (~2,300 y.a.): Plants gain mass by taking it from the soil… Johann Baptista van Helmont in 1600’s Supporting Evidence: Plants need soil to grow. If roots are removed, plants die. After several years of cultivation, soil loses its ability to support plant growth.

The Rules of Strong Inference: Strong Inference is a method for looking at scientific problems by trying to disprove hypotheses and accepting the hypotheses that can not be disproved. Using Strong Inference entails following these rules (from an article by John Platt, 1964): 1. Devise multiple hypotheses. 2. Design experiment(s) to eliminate one or more of the hypotheses. 3. Carry out the experiments in a manner that gives a clean result. 4. Repeat. Refine hypotheses.

The Question: Can your hypothesis be disproved? What experiment(s) can disprove your hypothesis?

What is the world made of?

Nothing… …if the earth is the nucleus of an atom, the electrons are twice as far away as pluto

CB 6.2 http://video.google.com/videoplay?docid=6945724039283018435

protons neutrons electrons CB 2.4 Atoms are made of: protons neutrons electrons

CB 2.8 Each element is defined by the number of protons, has an equal number of electrons, the number of neutrons may vary.

CB 2.2 sodium + chloride = salt

Atoms can be combined together to make molecules

The Periodic Table of the Elements

How do atoms form molecules?

CB 6.2 http://youtube.com/watch?v=yCfDRvDWid0