Grade 9 Chemistry

Chemistry in Grade 9 becomes an explanatory subject. Instead of describing what substances do, students begin to explain why: why sodium chloride conducts when molten but not when solid, why a noble gas does not react, why a reaction reaches equilibrium rather than finishing. The atomic model is the tool that makes those explanations possible, so it is taught slowly and used constantly.

The most common difficulty is the language rather than the ideas. Students mix up atom, ion and molecule, or read a formula without seeing how many of each atom it contains. We correct this with a great deal of written practice, because fluency with symbols is what makes the later chapters readable.

By the end of the year students should be able to write and balance simple equations, work out the electron arrangement of the first twenty elements, and predict whether a displacement reaction will happen.