Chemistry
High School (9–10)
General
Atoms and Molecules › The Mole ConceptAtoms and Molecules › Molecules, Ions and FormulaeAtoms and Molecules › Laws of Chemical CombinationChapter 3Contains Standard contentAtoms and Molecules
Burn a candle, and the wax seems to disappear. Does matter really vanish in a chemical change? In this chapter we meet the two laws that scientists found by weighing before and after a reaction. They lead us to the atom, the tiny particle that every element is made of. We learn how atoms join to form molecules and ions, how to write a chemical formula, and how chemists count atoms with a unit called the mole. Python helps us with the calculations.
Part of Chemistry · High School (9–10) (chapter 3)
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Laws of Chemical Combination and Atoms
Two centuries ago, scientists weighed substances before and after a reaction, and they found rules that never fail. Here we learn those two laws, and the idea of the atom that Dalton built from them. We also learn how heavy an atom is, in a unit made for it.
Molecules, Ions and Chemical Formulae
Oxygen in the air is not a single atom, and salt is not made of molecules at all. In this course we see how atoms join to make molecules and ions, and we learn to write the formula of a compound from the valency of its parts.